METHODS AM SYSTEMS FOR DAMPING OSCILLATIONS OF AJPAYLOAD

CROSS .REFERE CE TO RELATED APPLICATION f9iWl| Hie resent application elairas priority ¾ .S. Provisional Application Mo

62/385·, 856 fil d on September % 2016 sad to I ^; .S. Parent Application No. 15/ 89,2 0. filed

^• Oft December 22, 2 1i , ie cooteM of wlheh are incorporated here »-¾y references in their entire ties.

CKGROt D

8O021 A liaraaaoed veiH e, .Which may also be referred to as aa atitoeoBKj vehicle. Is a. vehicle- -enable of travel witlw a pl^ysically-presont h«i«ati operator. Art unmanne v$rfcjte .ina operate m a remote-control mode, in a»i aataoomoas mode, or in a ^• partially autonomous nrode.

(00031 When m ufajaaaaed vehicle- · cperates. in. a remote-control mode, -a pilot or driver that Is at a remote loeabon can control the iraniaaued vehicle via so iinauds that are seat to the xm mneA vehicle ^' vi a wireless link. When, the o» manned vehicle operates in autonomous mode, the unmanned vehicle typically moves Based on pre-pTOgraoi!iied navigation waypoisiS. dynamic automation systems, or a combination of these. Further, some unmanned vehicles can: Operate in ^' both a remote-eOiiiro! mode and an autonomous-- mode, and in some instances may do so si muliafteo sl . For instance, a remote pi o or driver rrtay wish to leave navigation to an antonomotis system while manually petfonning another task, sneh as operating a mechanical system for piekisg up objects, as an exaniple.

}M04| Various ty es- of »n»iarraed vehicles exist fer various different environments,

For iastartee, unmanned, velieiss exist for operation in the ai , n the. ground, underwater, and in space. Examples iacia e aa4.-eo iet¾. ati^ tail-sitter U ^-amoag .others. lhaaa»a.ed vehicles also exist for hybrid operations ia. Which o>nlti-environmerit operation is possible, Examples of hybrid iirmiantre vehicles Include an amphihioa craft that is capable of operation on land as well as on water or a. fie platse that Is capable of landing on water as well as on land. Other examples are also possible. SUMMARY

{OOuSJ Example kipiemeafafeas »iay relate to various techntqaes for .dam ing oscillations of a pa iid co ipied to a tether of a winch, system arraaged on aa yj ianned aerial vehicle (tlAV). For example, t¾e UAV's control system tflay dampen th oscillations by causing the UAV to switc to; a forward flight mode iii which ntoveme of the UAV results ia drag on the pay load, thereby darapiag the oscillations due to the drag, in another ewffiple, the control system may cause the UAV to reduce m extent of flight stabi ^' llgatiori along at least one dimension, thereby resulting m damping of the detected: oscillations due to energ dissipation during niavenieni of the IIAV along the at least, one dimension, in this w y, the control system could select a d carry out one or niore suslj iechniques, anti e««ld do so during retrac tion and/or deployment f the tet er,

|0¾86 to one as ect a system is provided. The system may includ a winch system for an aerial vehicle, where the winch .system includes; (a a tether disposed on a spool, (b) a motor that is operable to apply torque to the tether, and (c) a pay load coupling apparatus coupled to a leading end of ^" the tether and strucmreil to mechanically couple ay.foad to the tether. The system may also include a control system operable to, white the aerial vehicle is la a hover fligh mode, switch to operation In a tether retractio mode. The control system is also operable to, while operating in the tether retraction mode, perform a damping routine to aro en oscillations of the payload coupling; apparatus.

{§Q&T\ & another aspect, another systeai is provided. The system may include, a winch system for an aerial vehicle, where the wiach system includes : (a) a tether disposed on a spool and (b) motor tha , is operable to apply tpt¾«e. to the tether. The system ma also include a control system operable to, while the aerial vehicle is in a hover flight mode, cause the aerial vehicle to switch from the hover flight .mode to a forward flight mode in which «jo vement of the aerial vehicle results in <fcg. on a pay load that is coupled to the tether, where the drag dampen oscillations of the payload when the tether is at least partiall umvonud,

{0008] In yet another aspect, yet aiKJiher system is provided. The systeat may include a witieh. system for an aerial vehicle, where the winch system mel tides: (a) a tether disposed on a spool and (b) a motor that is operable to apply torque to the tether, and where the aerial vehicle Is operable in a ;position¾> mode in which the aerial vehicle substantially maintains a physical position during hover flight by engagin in flight stabilization along three dimensions at physical space. The system may also: include a control system operable to, while the aerial vehicle is in the position-hold mode, cause the aerial vehicle to redisee art extent of flight stabilization along at least one of the three dimcasioiis, thereby -result¾ig in damping of oscillations of a pay load dueio energy dissipation -daiiHg movement of the aerial vehicle along the at least -one dimension, where the payload is■ ^■ coupled to the tether, and. where the oscillations occur when the tether is at leasi partially nwo nd.

}0i¾s>| In yet another aspect, yet another system is provided. The system .may include a winch system for a aerial vehicle, where the winch system includes; (a) a tether disposed on a spool and (h) a motor that is operable to apply torque to the tether. The system niay also m.eJ«de a control system operable to _s while the tether is at least partiaily unwound, select, one or more damping romiffes :fl¾i¾ a plurality of available darnping routines to dampen oscillations o a payload that is eotrcled to the tether.. The eo»tto! system is also- operable to perform the ose or mo e selected damping routines.

JOMOf Irs yet another aspect, yet auaiher system is provided. The sysiem may include means for, while an aerial vehicle is in a hover ^' Sigh mode, switching to operation in a te her refraction mode. The system may also include means foi, while operating in the tether retraction mode, pertomliug a dampin routine to dampen oscillations of a payload coupling apparatus.

| €l I ¾ I ί» yet another aspect,, yet another system is provided. The system ruay include means for, while aerial ehic e is in hover fight o e,* causing the aerial vehicle to switch Irani, the hover flight mode to a for a d flight mode i which movement of the aerial vebieie results in drag on a payload that is coupled to a tether, where the drag dampens oscillations of the payload when the tether is at least partially unwound.

$ 12$ In ye anothe aspect, yet another system is- provided. The system ma include means for, while the aerial vehicle is in a position-ltofd mode, causin the aerial vehicle t reduce a -ekfcenfc of flight stabilization along at least one of three dimensions, thereby resulting in d ping of oscillations of a payload due to ene gy dissipation during movement of the aerial vehicle along the at least one dimension, where the payload. coupled id a tether, and where the oscillations occur when, the tether is at least partially unwound.

(0013 1» yet another aspect, yet another system is provided The system .- ay include tneaos for., while the tether is at Iesst jar iaily unwo n *, selecting one or more damping routines from a plurality of available damping routines to dampen oscillations of payload that is coupled to a tether. The sysiem may also include means for performing th one or more selected damping ^' routines-.

BME ESC FtiO OF THE DRAWINGS j¾ J5J Figure 1 A is a _: simplified iiosiratioii of an unmanne aerial vehicle, according io aft example embodiment.

{00½{ Figure IB is a simplified iUusir&tion of aa anmaaned aerial vehicle, according to an example eaihodhne .

f -00.17} igure 1 C is a simplified, lkisiratiaa of aa mma ne aerial vehicle,, accx>rdiag. to a¾ example . embodiment-

|0O18 J Figure D Is & simplified lllwstraif on of m uimianned: aerial vehicle, according to an example e hodimesit

f0019{ Figure IE is a simplified illnsitatioH of an usmaaned aerial vehicle,, according to an example embodimeat.

{0820} Figure 2 is a simplified bloek diagram illustrating components of an unmanned aerial vehicle, according to an esaaTple enibodimeni,

{0021} Figure 1 is a Sim lified block: dia m! i-l iusteui 1.1ΑΎ system,: according id an example embodiment

|M22f Figures 4A _S , and 4C show a payioad deliver apparatus, according to example eai odttnei tS;.

|0023§ Figure SA &kows a espective view of a payioad delivery apparatiis 500 including payioad 510, accordin to an exam le- erttbodinrent.

fO02 | Figure 5B i s a cross-sectional side view of payioad delivery apparatus 500 and payioad.510 shown ire Figure SA.

[00251 Figure: 5 is a side view of payioad deliver apparatus 500 and pay load 51.0; shown in Figures SA and SB.

{002$} Figure OA is a _: perspective yiew of pay! oad eoupiing apparatus 800, according to an example erefcdteenr.

{0027} Figure 6B is a side view of payioad eoupiipg apparaiMs 80§ shown, in Figure j002S| Figure: 6C is a tent view of pa ioad couplin apparatus 800 shows in Figures

OA and 6B.

1 Figure ? is a perspective view of payload coupling apparatus 800 shown in Figures 6A-6C;. prior to insertion into a paytoad coupling a p atus receptacle positioned i» the fuselage of a UAV,

|9i30f Figure 8 is another perspective view of payioad coupling apparatus W® shown in Figures 6A-6C, prior to insertion into a payload eoupiirig apparatus receptacle positioaed ia the feelage: of a tJAV.

(0031.1 Figure 9 shows a perspective view of a recessed r strain! slot aui payioad coupling apparatus reee iacic poslftoued in a faselage of a DAY _*

j _, 8032| Figure 1ΘΑ shows a side view of a p-ayioad delivery apparatus 500 with, a handle 511 of payload 510 secured within, a pay load coupling apparatus 800 as the payioad. 5 !·ø -ittoves downwardly prior to toacHirg dowa for delivery,

{0033 j Figur 1 OB s ows a side view ef pay toad delivery apparatus 5( 0 after pa load 510 has landed on the ground showing payload coupling apparatus 800 decoupled froro handle .51 1 of payload 510,

Q03 | Figure IOC show a side view e payload delive y apparatus 500 with payload coupling apparatus S00 iBoving away tkro handle 511 of payload 51.0.

ffHBSf Figure 11 is a side view of handle 11 of paytead 10.

Q¾36J Figure 12 shows a _: pair o locking pins 570, 572 extendin throug holes 514 sad.5 i≠ handle 511 of payload 510 to secu the handle 511 and top of payload S 1 w tSwri tile fuselage of a UAV.

[003?] Figure 13 A is: a perspective view of payioad eoupiirig apparatus 90 prior to having a handle of a payload positioned within slot 92Ό of payioad coupling apparatus 90!). j0038j Figure 13B Is a perspective view of payioad eoupiirig apparatus 900 after delivering; a. payioad and decoupling: frc a handle of a payioad.

|0#39f Figure 14A is a tent perspective view of payioad couplin apparatus 900 shown in Figures 13 A an 13 , according to M esaurpie ehihodittreut,

|004i | Figure: 14B is a rea perspective view of payload coupling apparatus 900 shown in Figlsre 14 A.

f W4i I Figure 14C is. a side view of payioad coupling apparatus 900 shown in Figures

1 a 14B,

}9042| Figure 14D is a Irpat vie of payload eouplio apparatus 900 shown in.

Figures 1 4-140, {0043 Figure. I4E is a top view of pay load coupling apparatws 900. showri ia Figures

14A-D.

{0044}■ Figure ISA Is a perspective vie of payload coupling apparatus 1000, according to art exam le embodiffieiu.

jfl Sj Figure I SB is another perspective view of pay½ad cou lin apparatus 10

.shown in Figure ISA,

{0046} Figure ISC is a side view of payload c tJfKag apparatus 1000 ^' sho n in.

Figures 15A aud 1 SB,

{0047} Figure 1,5 D is a top view of payfead coupling apparatus .1000 ^' shown its

Figwres 15A- ,

f004Jj Figure BE. is a cross-seetioual side view of p ay load corrp!iBg apparatu s 1.000 shown in Figures- 15A~D.

} 49| Figure, ί 6 A is a side view of payload coupling, apparatus #00" with a lot 8 8 positioned above lip 806\ aeeordrug to rn, exam le emb dimen

{0050} ^' Figure 163B is a side view of payload eoppllrtg apparatus SOCf after slot 8 8 has -been clo sed ^' following decotip ag o f pay lead ceupliag apparatus O ' torn a h andle of a payload,

{005Ϊ] Figur 1 bC is a cfoss-seeiidnal side view of payload coupling, apparatus S0(f shown i Figure J 6 ^' A.

Q0S2i Figure 16D s a cross-sectional side view of payload coupling apparatus 800' shown in Figure 16 ,

{O053J _. Figure 1 ? is flow chart of a Method for carrying out teiaered pickup of a payload. for subseque t delivery to a target location, according to an example- embodiment: {-0Ο54| Figure 18 is a .flow ^' .chart of a a»thod fo -carrying- out tethered delivery of a payload., according to aa example eiabodsmeat.

}0OS5J Figure 19- is an example ^' flowchart for facilitating ^' control of the tether for purposes of leieraciing with, a¾d or providing feedback to a user, -according to aa examp e embodiuie t..

{005 f Figure Ί0 illustrates a motor current level over t»i% accordkg I» aa. exatnple embodiment

}¾857| Figure: 21 Illustrates a detected current spike that is Judicative of a particular user-iuteractioa with a tether,, according to aa example embodimeat

|0OS8 ^' Figure 22 illustrates a raotor response based pa the particular user-inieraeEiOii, according to aa example embodimeat. f00S9J _. Figure 23 illustrates ii motor response- process to adjust tension of fee tether, according to aa example e bddlmeat

Figure 2 illustrates a motor fespoitse process io provide the feet of a detent., cced ng to aa example embodiment.

}0M1| Figure 25 illustrates a motor response process followed by a IJAV response process, according to an -exampl embodiment

|0<}62| Figure 26 is a ¾w chart of a. method or determiniag whether a pay!oad has- detached from a teiaer of a UAV, aceordiag £o example e bodiment.

00631 Figure 27 is im example $¾wefesit for i tiatia a daftspiag: routine to da«¾pea oscillations of a jp l ^d: ^ j^ti^-^P ^ ³ ^^ -aceot^iag.- to a esarapfe ero odiraeot.

|0Μ4| Figures 28 to 28D cotiectiveiy illustrate Initiation of. a damping routine during a tether retrae&m process, according to .an example embodiment

JOMSJ Fi ure 29 is an example fl wchart for initiating forward flight to- dampen oscillations of ayload, according to aa es n^le embodiaieat:.

|0<f )| Figures 30A- to 30D collectively- illustrate nse of forward ^' Sight to dampen oscttlaticas of a payload, according t aa e m le erabodaaent.

{<lKN»7j Figure 31 is aa example .flowchart: .for rcdKcisg aa extent of flight sta%iji¾aiioft to dampea oscillations of a payload, according to aa example embodiment

|0¾68| Figures 32Ά to 32H collectively iltus&ate use of rednetiOB m the extent of flight: staijjhzatioa to dampen oscillations of a ayloail, according t example embodiment 9i 9| igu e 3 is art example flowchart for selectin one or mote damping routines to hel dampen oscillations of a pay toad, according to an exa le embodiment

[00701 Figure 3 is a flow chart of a method fo deiaehirig tether from a IJAV, according to aa example embodiment

|0¾7:l} Figure 35 is a flow chart of a method for detecting and addi¾ssiag downward feces on. a. tether when lowerin & payload toward the groirnd, according to aa example em odiraent

O72| Figure 3 & is a flow: chart of a raethod for delectin . aad ddressin do nWard: forces on a tether .when winching a payioad toward a IJAV, according to a exam le e ibod fflCBt

f§#?3£ Figure 37 is a flow chart: of a metkod for detecting whether a OAV has successfully picked up a payioad, accordin to an example embodiment

|Θ$?4| Figure 3SA illustrates -avportios of a state diagram of a II A V carryiag ,o»t a payload pickup aad delivery process, according to an example erabodimsBi J0075;j Figure 38B illusiraies■ another portion: of the siate diagram ·»£ a ϋ A V carrying out a psyioad pickup - ftd delivery process, according to a» exaisple emhoditaedt.

.[0076J Figure 38C jHastt¾fces. another portion of the state diagram of a UA V carrying ^■ &at a pay load piekup and delivery process, accor in to a» example er!abadiMeM.

fu¾?8| The present embodiments are related to the use of unmanned aerial vehicles

(UAVs) or urmiamied aerial systems (UASs) (referred to collectively herein as ^" UAVs) thai are user! to cany a payload to be delivered or retrieved;. As examples, UAVs m be used to deliver or retrieve a payload to or from an individual or business. In operation the payloa to be delivered is secured to the UAV and the UAV is then IIOWB to tbe desired delivery site. Osee the UAV arrives -at the deliver shs^ the UAV may land to deliver the- payload, or operate in a hover tirade aad lower the payload frora the UAV towards tbe delivery site usrug a tether and a winch mechanism posiiased with the UA V. Upon toaeadowu of ifee payload, a payload. coupling apparatus, sometimes referred to as a "capsule,' ^' ' is aisronla&ally decoupled ^" the payload. In addition, the payload may be retrieved while the UAV is operating in a hover mode by positioning a ^' handle of tile payload filto a slot in the payload coupling apparatus.

|00?9$ bt order to deliver the payload, the UAV amy iisc!ude various tuschaiiisms to secure the payload. during trafisport and release the payload upon delivery. Example embodiments may rake the form of or otherwise relate to au apparatiis for passively coupling a payload to a U AV fbr transport and releasiag tire payload upon delivery,

f 0089} Such a payload coupling apparatus may inelude a housing coupled to the UAV b a tether that may he wound and aiwound to raise and lower the housing with respect to: the UAV, T ie .housing may include one or more swing- arms adapted to extend from the housing at aa acute angle _* formin a hook au which the payload may be attached. hen the housing and attache payload are lowered tk»a the OAV e,g,, b isswlnding the lether) to transport location below the UAV (e.g. ,. the ground), the payload may detach from the hook. [0081! For insiasce, ouee the payloa aehes the ground, the UAV y ovee-tm the tetter by eotriifnung to ittiwisd tlie tether. As tlie payload rentarns stationary oP the grouisd, the payload coupling .apparatus ruay vmfim* t lower;, and a gravitational andpf an isertial. force on the homing Ma cause the swing arm book to detae from the payload.. Upon detaching from the payload, the .swing arm may be adapted, i retraet into the housing, a«d the payload coupling app ratus ma ascend (e.g., fey retracting the tether) toward the UAV, leaving tbe payioad OH tbe ground. As the payload. coupling apparatus approaches tbe UAV. a device adapted to receive the ^' bous ng may engage a cam. of the swing arm causing the swing im to extend fro die housing at as aesie angle, thereby forankg a ook for secMin another payload for delivery by the UAV,

(0082 More specifically., die present embodiments advantageously include a unique payload coupling apparatus. in oae en#odiment, the payload coupling apparatus includes a slot downwardl extending from an outer surface of the payload coupling apparatus towards a center of the payload coupling apparatus. The slot is dapted to receive a. handl of a payload, and supports: the payload during delivery or retrieval of the payioad:. Once the payioad re ches die ground, the payload coupling apparatus continues to move downwardly until the handle of the payload is decoupled from ite slot of the payload coupling apparatus. An outer surface of a lower lip berieaib the slot is undercut such that: It extends less than the outer surface of the upper end of the payload coupling device above the slot to prevent the payload coupling device front reengaging with the handle of the payload during retrieval ^' of di payload coupling device to tbe UAV. or with eatclnng oa power lines or tree branches..

[0β83 The _: payioad coupling apparatus may include earns positioned on opposite, sides of an outer surface thereof. As the payload coupling apparatus i winched, back to the UAV, the earns of tbe payload coupling apparatus are adapted to engage wi th corresponding cam w tibia the fuselage of die UA suck that when the cants engage, the payload coupling apparatus is able to rotate to orient the payload coupling apparatus in a desired position within the mseiage of the DAY,

1008 1 In this regasd. the payload may have longintdinally extending to such itat when the caw on the outer surf ce of tbe payioad couplin apparatus engage the mating cams within the fuselage of the UAV, the fengitodmatly extending top is rotated into a desired position within a corresponding iongttedinally extending recessed restraint slot in the bottom of the fuselage of the UAV, In other embodiments, the payload may be simply drawn Into a tight positioniag against tlie bottom of the fuselage of the UAV. In such cases, the top of the payload is not required to nave a longitudinally extending top tbat becomes positioned

ID within a cavity ta the fuselage when tfec cams of the p ayload coupling apparatus are in •engagement with maitug earns within the fiiselage. However, where c ms are used the cams of the payioad coupling apparatus an d the mating casus within a payioad -coupling receptacle is the feselage may properly rotate the pay bad coupling apparatus to orient the payioad in a desired position with respect to tne _: fuselage,

|0$SS| A significant advantage of the payioad coupling apparatus is that the pay lead ^• couplin , apparatus includes no movi g parts^ thereby .redncing its complexity and reducing die possibility of part failure which exists w en moving parts are involved io a payioad coupling apparatus,

086 the payioad mm aclvaatageoasly inclade a handle that is well-suited for positioning within th slot of the payioad coupling apparatus. The handle n¾ry he eoiistruefcd of a thin, flexible plastic material having a high degree of flexibility; allowing fo easy nser ion into the slot of the pay ioad coupling mechanism, and also for easy decoupling from the slot of the payioad eoupling meclmnisrri neon tending of the payioad. Handle ^' flexibility is desirable to allow the payioad and payioad coupling apparatus to hang vertically straight as the handle bends to match the angle of the slot in the payioad; eoupling apparatus. A more rigid handle makes it easier for the payioad coupKag apparatus to decouple from the handle upon package landing, although it the handle is to flex le the payioad coupling apparatus could fli over and not release, Fiirtherr ofe, it is desirable that upon decoupling, the handle should spring hack to a vertical orientation which, further reduces the re-hooking of the handle with the. slot of the payioad coupling apparatus, and. to pull the package tight into the restraint when engaging within, the fuselage of the UAV. It should also he noted that the handle could also be out of paper or other natural fiber, with or wi thoat plastic lamination or piaslic/giass aatural fibers fo extra strength, As■ aa example, fiber reinforced paper may he used as well,

j(M>8?) The handle may also advantageously include a pair of ho les that are adapted to receive lockin pins positioned within the IIAV . The locking pins may have a conical shape to facilitate insertion into the hole is the handle- and to pull the paekage into tight: engagement within the recessed restraint slot in the fuselage of the -OAV. Once the earns of the payioad coupling apparatus are engaged with the mating cans within the fuselage, the handle is positioned in the desired orientation. A. servo motor or other mechanism such as a regular electric motor with a leadscrew, or rack and pinion with limit switches to control travel (or other meehauism such as a linear actuator) may be used to move the conical locking puts through the h les in the handle to hold the handle and payioad beneat tightl in ^• pdsifioa, allowing far high speed flight of the UAV when ihe payload is secured heseath the UAV. Alternatively, the locking ^' pirn or pin. (mild be moved to position within a recess of opening to the payload eoypllng appara ts itself, rather than into holes is the handle of the of the package id secure the payload eoupiing appanittss ai¾d package to the UA V,

|OT88| The pay toad rnay take the fe tr? of aerodyaatnie tote, although the payioad may have any «uniber ^: of ίϊ«¾ηί configurations and geometries. However, where a linear recessed restraint slot is positioned! with the fuselage, it is desirable that the top of the payioad has a generally linear shape to fit within the linear recessed .restraint slot within the fuselage. 0®8 J The pa load coupling raeehaoisrn may ave: difiererit configuia iQus as well

For ex m le, ^, tether may he attaehe to a hottots of the payioad eoupliag a paratus, a is positioried - within a vertically extending tether slot in the payload coupling apparatus. Th vertical tether slot extends through; the payload cowphng apparatas that is adapted to receiv a handle of a payload, in this position, the handl e of the payload is positioned; within the slot during delivery and retrievai The payioad coupling apparatus als includes a. pair of upwardly extending fingers positioned about the slot with an opening between the pair of fingers^

|0{$ f Wfjeti the payload touches the grotiud, the payload eotipSing apparatus- continues ¾ move downwardly and: autoinatlealy is decoupled from the hasdle of the pay bad. The pay load conpiitig ap afatus may include a top lf that is weighted, s«eh that upon decoupling torn the handle of the payload, the payload conpHsg apparatus tips over and: rotates I SO degrees such that the pair of upwardly extending fingers are rotated 18 and extend: downwardly.: During this rotation, the tether becomes disengaged, front the vertical tether slot and moves through the opening between the pair of fingers, As a result:, the payload coupling- is prevented from reengaging with the handle of the payioad because the slots exiends downwardly., in addition, die downwardly extending slot after release f the: handle also helps to prevent the payload coupling apparattts from engaging with power lines or tre branches as it i winched back to the UAV _* because the opening in the slot extends downwardly. Alternately, the payload coupling apparatus May be bottom weighted

0091| This embodiment of the payioad eoupthig apparatus am also include cants o an onto" surface thereof adapted to engage mating cams withto a. payload coupling apparatus reeeptaele within the fuselage to orient the payload coupling apparatus in a desired position withi the fuselage of the .UAV.

ffW9¾ Irs another emhodinient, a vertical slot uiay he positioned within he: payload coupling apparatus adapted to receive a hande of a pa load and to support the handle and

alignment enables high speed forward flight, after ick u . The alignment ¾ accomplished through the shape of the payload hook a¾d receptacle, The hook (also- called capsule dee to its shape) has cam features around its perimeter which always orient it i a defined direction when it engages into the cam fe ures inside the receptacle of the fuselage of the VSA . T e tips of the earn shapes oa both sides of the capstile are asyn retric to prevent jafemsng. in the 9& degree orientation.,. .¾¾. this regard, helical ^' cans surfaces may meet at mm on one side of the payioad: coupling mechanism, an helical cam surfaces may meet at a rounded, apex on the ether side of the payload conphng mechanism. The hook is specifically designed so that fee package li nas in the eenterltne of the hook, enabling alignment in both directions f m 90 degrees.

|Θ094| Besides the alignment functionality,, the payload hook also releases the package passivel m d atitoniatieally when the package fetiches the ground upon delivery. This is accomplished through the shape and angle of the hook slo and the co«espo.udiug. handle on fee package. The hook; slides off the handle easil when the payload touches down dne to the mass of the capsule and. also the hiertia wanting to eontinne moving the capsule downward past the package. The end of the ook is designed to he recesse slightl from the body of the capsule, which prevents the hook front accidentally re-attaching to fee handle. Afte stieeessfttS. release, th.e hook gets winched hack up Into the aircraft All thi funetionaiity (package alignment ^'" during pickup and passive release during delivery) may advantageously be achieved without any moving parts in this hook embodiment (referred to as a solid state design). This greatSy increases reliability and reduces cost. The simple design also makes user interaction very clear and, self-explanatory. In addition the payload coupling apparatus tmy be bottom weighted si? "that It ^' mains itt a desired ve tical orientation and does nor tilt.

j0 95f The package used for the which op/pick up operation ma be an aeradynarrtiea!ly shaped tote with a reinforced snap-in handle (e.g. Made ant of plastic or other materials .such as fiber), -although other shaped pay l oads slay also be used. The handle of the pay load attaches the payload to the hook of a payload coupling apparatus and its slot or opening is shaped to allow for a reliable passive .release _* The andle also ma include two sntal ^' ler openings for locking pins,:. The reinforcement of the handle is beneficial to transnnt ike torque from the capsule ½to the package during die alignment rotation. The package Itself saay he made out of caidstock and have an irjterual tear strip, The t » Sher tape fear strip may tun along die erimeter of one package side and ena es the customer to open the ackage easily alter delivery.

When the payload is witrched u and alignme t is completed,, the payload is piil!ed into a recessed restraint slot in the ftseiage of the UAV, using the additional vertical tra vel of the capsule in its receptacle . The recessed rest ai t slot matches the shape of the upper portion of the payload nd stabillsies it during cruise flight, preventing any excess side to side or back and forth sway motion The recessed restraint slot is als completely recessed Into the fuselage and has no protruding parts, allowing for good aerodynamics on- the return flight (after tire package has beers delivered).

f 0iJ#7| The present embodknents provide a highly integrated winch-based piekij and delivery system- for UAVs. . number of ^'' significant advantages may be provided. For example, the ability to pick up and deliver packages without fie need for landing is provided. The system is able to winch up a package with the aircraft hovering. There also may be no need for inirastreeitue at the merchant or customer in certain applications. The advantages Include high Hussion flexibility and the oiemial for lituhed or no iafras ^' &ueiure installation costs, as well as increased flexibility in. payload geometry.

II, llJustrative llntuanaed Vebieles

f0 8f Herein, die terms %ur«annesl aerial vehicle" and '-UAV" refer to any autonomous or semi-atitoriornous vehicle that is capable of per&nning some functions without a physically present human pilot.

} S*9] A U AV can take various forms. For example, a T V may take tfie form of a fixed- wing aircraft, a glide aircraft, a tail-sitter aircraft, a jet aircraft, a ducted fan aircraft:, a ighter- hari-air dirigible such as a blini or ste-sra ie balloon, a rotoreraii sues as a helicopter or multicopter, and/or an omiihopter, among other possibilities. Further, the terms 'Worse, ⁵ ' section: to provide lift for the UAV 120, a vertical siaMMzer 126 (or fin) to stabilize tine plane's yaw (torn tert or right), a horizontal stabi se 12$ (also referred to as an elevator or tallplane) to stabilize pitch (tilt up or down), landing gear 130, and a propulsion unit 132, which can include a motor, shaft, arid propeller,

pieSf Figure iC shows an example of a UAV 140 with a propeller in a pnsher coB iguraiiori. The term "pusher refers t the fact that a propulsion unit 142 is mounted at the back of the UAV and ''poshes ^*5 the vehicle fcrward, in contrast to the propulsion unit being mounted at the trout of the UAV _t Similar to the deseription. provided for Figures A and IB. Figaro iC depicts eouuuon structures used in a pusher plane, including a fuselage i 44, t o wing 146, vertical stabilizers i48,.a»d ihe pi¾pulsioa turn 142, which can inehsde .motor, shaft, ami propeller.

010 1 figure ID shows an example of a tail-sitter UAV MO. In he illustrated example, the taiS«sitter U AV 160 has fixed wiags 162 to provide lift and allow the UAV 160 to glide- fcori-^a&Hy-(e, > _> along the x~axis _s in a position that is appr05i.iffia.tely perpendieui.ar to dse position shown in. Figure ID), .However, the fixed wings M2 also allow the tail-sliter UAV 1 0 to take off and land vertically on its o n.

|θί07| For exarnple, si launch site, the tail-sitter UA 160 ma fee positioned vertically (as shown) with its fins 1.64 and/or wings 162 restiBg on the ground, and stabilixin the UAV 160 in the vertical position. The tail-sitter UAV 160 m y then t ke of fh operating lis propellers 166 to generate an upward . ^' thrust (e.g., _; a thrust that is generally along the y- axis}:. CJnee at a. suitable altitude:, the Mil-sitter UAV 160 may use Its flaps 168 to reorient itself in a horizontal position, such that its fuselage 170 is closer to being aligned with the JS* axis than the y~axis. Positioned horizo tally, the propellers 166 may provide forward thrust so that the taihsi tier UAV 160 ean :iy in a similar manner as a typical airplane..

1 _. 1081 any variations on the illustrated Slxed^wing UAVs e possible. For instance, ftsed-wing UAV may meludc mo e or fe er propellers, artd or may utilize a ducted, fan or multiple ducted fans for propulsion,, Farther, UAVs with more wings (e,g., _t an "x-wing" eOnfiguratiott: with four wings), with fe er wings,, or eve witn no wings, are also possible.

[0109} As- noted above, some embodiments niay Involve other types of UAVs, it), addition to or in th alternative to fixed-wing UAVs. For instance. Figure IE shows an example of a rotoreral that is commonly mferre-d to as a muitieopter 180, The nu tieopter 180 ma also he referred to as a adcopler, as it includes four- rotors I 2, it should be understood that example embodiments may involve a retoreraft with more or fewer rotors ihati the n«iltieopier ΙΒΐΧ For example, a helicopter typ cally has two rotors. Other exam les with: three or more rotors ate possible as well Herein, the terra '¾dticOpfe ^s refers to amy rotorcfari having store i m two rotors, a id the term "teiicopier" refers to ixito craft having two rotors,

}0110| efcfring to Ore mtdticopter ISO ki greater detail, die four rotors 182 provide propulsion aad raaneuverafeilhy for the sBulticQpter 18(1 .More specifically,, -each rotor 1 S2 ncludes blades that are attaelied to a motor ; 84. Configured as s«ch, the rotors t 2 _: may allow the mwltieopter 1 SO to take off aud: land ifertie liy, to maneuver in arty direction, and/or to hover. F ther, the pitch of the blades ma be adjusted as a. group and or diifeerdally, and may allow tfte multieopter 180 to control lis pitch, roil, yaw,, and/or altltwde.

j¾l 11- it should be understood tliat referesces herein to an ¾lrnauoed" aerial vehicle or UAV ca apply equally to autouomous and .serni-autonomoKS aerial vehicles, in an atitonomous im lementation,, all functionality- of the aerial vehicle is automated; e,g. _s pf¾- progi'anuned or controlled; via real-time computer fuacttoftait - thai responds to input from ^• Va ious sensors and/or pre-determihed Intonation. lv¾ semi-autonomous implementation, some mnetions of aerial vehicle a be controlled by a htttaan operator, while oilier functions: are carried out autonomously,. Further, ¾· some e tibodunetits., a UAV ay he eonfigitred to allow a rearote operator to take over funetiors that cm otherwise be controlle autonomousiv hy the UAV Y et rarthet, _: a given type of functi n may be controlled reasotely at one level ^' of abstraction and perfornied aMenoniously at sodi r level of ahsiraetiOiJ. For exam le, a remote operator eonld eosfro! high level navigation decisions for a U V, suc as by specifying dial the UAV should travel from one location to another (e.g., ftam a warehouse hi a suburban area to a delivery address in a aearhy city};, while the UAV's navigation system autonomously controls more fiae-¾fai»ed. navigatio decisions,, such as the specific route to take between die two locaUosts, .specific Eight controls to achieve the route and a void obstacles while na vigating the route,, and so on

|0ii | More generally, it should foe understood that the example UA ^' Vs described hereirr are not intended to be limiting. E¾ar»pie erahodirnents may relate to, fee impletaerrted within, or take the form of any type of manned aerial vehicle,

ϊϊί, i «s rative tlAV Coaipooesits

f O l Of Figure 2 is a simplified- block dktgram illustrating component of a UAV 20(1, according to an example embodiment., UAV 29$ may Safes the form oC of be siatilar is form to, one of the UAVs li ⁾ 0 _? !¾!,. 140, 160, and: 180 described in reference to Figures I A- I E. However, U V 1M may also take other forms.

A. Settsors

f(H18J In -an illustrative cmbodHneiH, !MU 202 may include both an aceelerometer and a gyroscope, which may be used, together to determine an orientation of the UAV 200. In particular, tire aeceleroraeter can measure the orientation of die vehicle with respect to earth, while the gyroscope .measures the rate of rotation around an axis. I Us me commercially available in low-cost, low-power packages,. For instance, an JMU 20 may take the form of or include a nnniaturbe MieroEieetoMechanicai System (MEMS) or a anol!eetroMeehanical System (MEMS J, Other types of IM Js may also he u ilized.

|iB 119 An IMIJ 202 ma include other sensors, in addition to accelerometers and gyroscopes, which, may help to better deterraitje position and/or help to hierease autonomy of die OAV 200, Two examples of such sensors are magnetometers and pressure sessors. In some embodiments, a UAV amy include a Ie *power, digital 3-axis magnetometer, . which can fee used to realize an orientation Md:epe»derit eiectmsic compass for accurate heading information. However, oilier iypes of magnetometers may be utilized, as well. Other examples are also possible. Further., Bot that IJAV could include some or all of the above- described; inertia sensors as separate components from an IMIJ,

|0120| 0 A 209 may also Inelnde a pressure sensor or barometer, which can be used to determine the altitude of the IIAV 200. Alternatively, other sensors, such as sonic altimeters or radar altimeters, can be used to provide an indication of altitude, which may help to improve the aeenraey of aud ot prevent drift of an. IMI J,

l&tM l In a farther aspect, 1 ⁾ AV 200 mm inelnde one or more sensors that allow the [JAV to sense obiects in tie environment. Fo instance,, in the illustrated embodiment, LJAV 200 includes ultrasonic seRSor(s) 204. IJltrasoak seasor(s) 204 can determine the distance to an. object b generating, sotusd waves ar*d deteimintog tire time interval between transmission Of the wave and; receivin the corresponding echo off an object,. A typical application of an ultrasonic sensor for unmanned ve iet&s or Mils is low-level altitude control and obstacle avoidance, An ultrasonic sensor can also be used for vehicles -that need to hover ^' at a certai height or need to be eajpaUe of detecting obstacles. Other systems can: be ased t determine, sense the presence of _* and/or deiermiae the distance to nearby objects, such as a light detection and ranging (LID Ait) system, laser detection and rangin (LADAil) system, and/or an infrared or i¾rw rd-Iooiiing infrared (FOR) system, .ajaong other possibilities.

|0ί 22 J In some emfeodinrerits, IJ V 200 may also include one or more imaging systern(s):. For example, one or more still and/br video cameras may be atifeed by I.IAV 200 to capture image data from the IJAV 's environment;. As a. specific example, eharge _^ coupied device (CCD) eameras r complementary mem »«de-semieonduetor (CMOS) cameras can be used with umoartued vehicles. Such imagin se«sor(s) have numerous possible appliealioo.s, such as obstacle avoidance, localization techniques,, ground trackin for more accurate navigation (e^g., by applying optica! flo techruques to images.} _* video feedback, and/of image reeognitiou and processing, among other possibilities,

| i23| IJAV 20 : xaay also include a GPS receiver 206. lire GPS receiver ;2¾ may be configured, to provide dat that is typical of vveJl-kaom OPS. systems, such as the 0PS coordinates of the UAV 200. Such 6PS d ta ma be utilized by die l!AV 200 for various functions. As suck the UAV may use its CtPS receiver 206 t help navigate to the caller's location,; a indicated, at least in part, by the GPS coordinates provided by their mobile device. Other examples are also possible.

\9 Β,. avigation utl Locution Dctermmatson

{01241 ^' The navigation module 21 may rovide ftmetionality tot allows tbe UAV 200 to,, e.g.s move a ut its environment and reach a desired location. To d so, the navigation module 214 may control the altitude and/or direction of flight by eostroi!iiig fee .mechanicai features of .the UAV that affect fisgbt (e.g., its fudder(s), e}evaiof(s), aileronCs},. and/or -the speed of its propellesis)}.

}0:i¾SJ In order to navigate the UAV 200 to a target location, the navigation niodule

214 ma impiement var ous navigation teekuqws, sacl as ma -raise navigation and lpeaii¾ation 5ased navigation, for inst nce, With map-based navigation, itie UAV 00 inay be provided wit , a map of its ew r^nrReui wbieh nia then be used to navigate to particular loeauon on the map. With j:oeaittatioa-base navigation, the UAV 200 ^' m y be capable of navigating in an unknown enviroanient using localization.

navigation -may involve the UAV 20 building its own tmp of its environment and ealct ating its position within the niap and/or fee position of objects in the eaviro tmetjk For example, as a UAV 2 moves thr nighout its environment, the UAV 200 may continuously ^' use localisation t update its ma of the environment. This continuoas Mapping process n¾ay be referred: to as sim ianeous localization: and raappkig (SLAM). Other naylgau ^' ert techniques m y also be «rili»ed,

}§$26J In som eiiibodime s. the navigation reod e 214 may navigate using a teebnique that rebes on way point s. Is particular* waypoinis are sets of coordinates tha identify points in physical space. For instance, an ai^navigation waypaiat may be defined b a certain latitude, longitude, and altitude. Accordingly, navigation niodale 21 may cause UAV 20 to move from waypoint to v'ay oint, _: in order to Ultimately travel to a final destination. (e.g., a final waypoint i a sequence of waypoinfs),

fOiif l la a .. further aspect, the navigation module 214 and/or other components and systems of the UAV 200 roay be confi «red for 'localiaation*- to more precisely navigate to the scene of a target location. More specifically, it may be desi rable in certain situations for a UAV to be within a threshold, distance of the target location -where a payioad 228 is being delivered by a UAV (e.g., within a few feet cf ihe target destination). To this end, a UAV may use a two-tiered approach is which it uses a more-general loeation-detemrination. teebnique to navigate to a general ar a that is associated with the target location, and then use a more-refined loeatkn^determination technique io Identify and/or navigate to tbe target location within the general area.

should, adjiist its .mechanical features <e.g;., its md eris ., elevat r ^' s), aileron{.s), and/or ^' the speed of its propeMer(s)) in order to effectaaie snch movements. The remote computing system may then eommunieate such adjustments to the UAV 2M so it can move in the ■determined manner.

C. CoaiHiujikatioji Systems

J 04J Irt a further aspect, the UAV 2 includes one or more comniunicatioR systems 318:- The conrmitRieations systems 218 may iRchrde one of more wireless interfaces Eaid t one or rnore wireline: iaterfirces, whic allow the UAV 200 to eo tnaaieate via one or more networks, -Such wireless interfaces may provide far eomniMuieatiori under one or more wireless eomRmnica ioR protocols, such, as Bitietooth, Wifi (e,g., an IEEE 802.1 1. protocol), Long-Term .Evolution (UTE), W.iMAX (e.g., m IEEE 802 Jft starsdard), a radio-frequemcy ID (RP.IB) protocol, aear-fieid communication (NFC), aad r other wireless commnnicatioa protocols. Such wireline irjteifaces may include an Ethernet interface, a Universal Serial 8BS (USB) interface, or similar interface t eomnnmicate via a wire, a twisted pair of wires, a eoaxial cable, an optical link, a fibero tic link, or other physical connection to a wireline network.

j0135| IK some eniboditrieats, a OAV 2O0 may include c romtffi eaiios systems 318 that allow for oth short-range e r»nmnic¾tion and loBg-range commuaicatioii, For example, the IJAV 200 may be configured for sbott-rarsgs comimrajcafioiis ttsing Bluetooth a»d for long-range coramtaiicatioas under a CDMA protocol I» sneh as embodiment, the t!AV 200 may be configured to ftnictioa as a "hot spot;' ⁵ or in other words _* as a: gateway or prox between a remote support device aad one or raore data. Retworks, such as _: a cellular network, and/or the Iafei¾k . Cojiigured as such, the UAY 200 may facilitate data cpi¾muriieatioHS _: that the emote support device. wo«i.d otherwise fee «aabte to perform by itself:

fil j For example, the UAV .200 may provide a iF.i connection to a remote device, and serve as a proxy or gateway to a cellular service provider's data network, which the UAV might ^' connect to under an LTE or a 3G protocol,, for instance. The IJAV 200 could also serve as a proxy or gateway to a high-alttede balloon network _s a satellite network, er a combination of these: networks, araoRg others, which a remote device might not be able to otherwise access,

the items) . [013$¾ ϊύ some embodiments, the payload 228 -t y be attached to t¾£ UAV sad located substantially ontside of the UAV during some or all of a light by the UAV, Far exatnple, the package may be temefed or otherwise reieasafely attached belo the- UAV daritt flight to a target location, is an embodiment where a package carries oo s belo .the UAV,. the package may include various features that protect its contents from the eiwiroiinieat, reduce aerodynamic drag on fe system, and prevent the contents- of .the package from. shifting during UA flight,

JOi40| For instance, when; the payload 228 takes the fbmi of a package for transposing; items, the package may include gn outer shell constructed of water-resistant cardboard, plastic, or an other lightweight and water-resistant materia!. Further, ip order t reduce drag, the package may feature smooth surfaces with a po nted - front that reduces the frontal cross -sectional area. Further, the sides of the package may taper from, a wide bottom to a -narrow top, which allows- the packa e to se ve as a -narrow pylon thai reduces interference effects on. the wing(s) of the U AV, This may move some of the frontal area anil volume of the package away from the wing(s) of the UAV, thereby preventing the reduction of lift OR the wiag(s) cause by the package. Yet further, in some embodiments, the dnter shell of the ackage may be constructed kom a single sheet of material in order to reduce air gaps or extra m terial both of which njay increase drag on the system,. Additionally or alternatively, the package tnay include a stabiliser to dampen package flatter, This redaction is flutter t y llow the package to have less rigid connection to the UAV and may eanse the contents of the package to shift less dur n flight.

[0141 J In order to deliver the payloae, the UA may include a winch system 221 controlled by the tether control module 21.6 in order to lower the payload 228 to the ground while the ^' UAV hovers above. As shown in figure 2, the winch system 22! may include a tether 224, .and the tether 224 .may be ooup!od to ^' die pay bad 22 b a payload coupling, appa tus 226, The tether 224 ma he wound on a spool that is eonpled to a motor 222 of the UAV . The motor 22 may take die form of a DC motor (e ., a servo motor) that can be activel controlled by speed cdn$aM«fc. The tether control module 2½ can control the speed controller to cause the rnotor.222 to rotate the spool thereby unwinding or retracting the tether 224 and lowering or raising the payload coupliag apparatus 226, In practice, the speed controller may output a desired operating rate fe.g., a desired RPM for the spool., which may correspond to the speed at which the tether 224 and payload 228 should be lowered towards the ground. The m t r 222. may then rotate the -spool so that it maintains, the desired operatin rate. f0142| Is order to control the m&t&t 222 via the speed controller, the tether control

•module 2ϊβ ma receive data from a speed seasor (e.g., an encoder) configured to eoiwert a mechanical positiou to a representative analog or digital signal, In partienlar, the speed sensor ma include a rotary encoder that may provide fo ation related to rotary position (and/or rotary movement) of a shaft of the motor or the spool coupled to the moto , a¾aostg other possibilities. Moreover,; the speed sensor may take t ie -form of an absolute encoder ■and or an incremental encoder, mmtg others. So m. an example implementation, as the motor 222 causes rotation of tlie ^' spool _* a rota y encoder may be used t measare this rotation. It doin so, the rotary encoder may be ^' Used to con vert a rotary position t an analog or digital electronic signal used fey the tether control .module- 236 t deterniihe the . -amo nt of rotation of the spool from a J¾a¾ i femme a le iot to as analog or digital electronic signal that: is representative of a new rotar position, among oilier options. Other examples are also possible.

|0l43f Based on ike data from the speed sensor, the tether .control: inodoie 216 tm determine a rotational speed of the motor 222 and'or the spool and tespoasively control the may vary the amotmt by which it adjusts the speed (e,g>, the RF ) of the spool, .md. thus may ^■ ty the de loyment rate of the tether 224, Other examples are also possible.

j0i45f IK some embodiments, the tether .control module 2X6 may be configured t limit the motor current supplied to the motor 222 to a maximum value. With such a limit placed on th motor cuweni _> there may fas skualioas w er the moto 222 eaunot opera at the desired operate specified by the speed: controller. For instance, as discussed, in more detail below, there may he .situations where the speed controller specifies a desired perati g rate at which the motor 222 should retract the teller 22 toward the UAV 2(M), hut the motor eurreut may he limited such that a large enough do u ard force on the tether 22:4 would counteract the retracting force of the motor 22% 4- cause t e: iether 224 to uuwiod instead. And as further discussed belo , a limit ou the tuolor current may imposed imd/or altered dependiag o?i au operatioual slats of the UAV 260.

f0|46 ΪΒ some embodiments, the tettser control modwle 216- ma be configured: to determme a states, of the tether 22 asd/or the payload 228 based on e amount of current supplied to the motor 222. For instance, if a downward, .forge is applied, to the tethe 224 (e.g., if the payio d 22S is attached t the tether 224 or/if the tether 22 gets saagged on an object, ett retracting toward the UA 206], the tether eoatrol utodtile 16 may need to increase the motor cnrrfent in order to. ause the determined rotational speed of the motor 222 and/or spool to match the desired speed. Similarly, wises the downward force is removed fk»» the iether 224 fe.g., upon deliver of the payioad. ^' 22$ or removal of a tether suag), th tether control module 216 may need: t decrease the motor current in order to cause th determined rotational speed o the motor 222 and/or spool t match the desired speed. As such, the iether control module 216 may he configured to monitor the current supplied ^' to the motor 222. For instance, the tether control module 216 could determine the motor current based on seasor data received from a current sensor of the motor or a eurreut sensor of die powe system 220, In asy ease, based oa the -current supplied to the motor 222, determine if the pay load 228 is attached to the tether 224, if someone or s methin - is pulling on the tether 224, and/or if the payioad; coupling apparatus 2 - is pressing against the UAV 200 after retracting the tether 224. Other examples are possible as-well

[M47f During delivery of the . payioad 22g. the pay load conpUng/ apparatus 226 can. be configured to secure the payioad 22 while bein io wered from the UAV by the iether 224, and can be further configured to release the payioad 228 upon reaching ground level. The payioad coupling apparatus 226 cas i eti be retracted to die UAV by reeling in the tether 224 using the motor 222, fO 148J In some ift^ieraemaiioas, ^' the pay load 228 may foe p ssively released o¾ce it is lowered to ttejptaniL For ex le, a passive release nieehanism my iaolude one or raore swing i ^' MS adap ed to retract into arid extend froni a hoasing:. Aa ex eaded swiag arm rnay ferm a hook on which die payload 228 my e attached, tfp . lowering die release mechanism and die payload. 228 to the ground via a tether, a gravitatioiial force as well as downward: inertia! force on ie release raedmmsm may cause the payload 228 to detach from the hook allowing ^■■ the release mechanism to be nhsed upwards toward the- UA The releas mechanism may further include; a ψ η$. meefenisro that biases the swing arm to retract into the housing when there are no other external, i rees ø¾ the swing arm. for instanc , a spriug ■ ^' my exert a force on tie swing arm ifrnt pushes or paii die swing mm toward, the feousiag mch that the swing arm retracts into the housing once the weight of the payload 228 no longer forces the swing arm. to extend from the housing, Reiraetisg the swing arm info th housing ma reduce i likelihood o the release tnecharhsm snagging (he payload 228 o other nearby objects when raising the release mec nism; toward die UA apon delivery of the payload 228.

}θί49| Active payload release mecha isms are also possihie. For sam ie _^ sensors such as a barotaeaie pressure based a!tirseter aad ot aceelerenieters may help to detect the position of the release nieehaalsm (and the psyioad) relative io the ground. Dat froni the sensors can be connaariicaied hack to the llA V ^' and/or a cofldo! syste over a wireless ak aa used to hel ½ determkiag whea the release meehanisra has reached groand level (e.g., by detecting a measurement wifti (he aeeeleroa efer that is characteristic Of ground impact). In other ex m l s, t e UAV may determine that me payload has reached the ground, based on a weight sensor detecting a threshold low downward force on the tether and/or based on direshold lo w measurement of power drawn by (he winch when lowering the payload..

|OiS0| Oilier systems and tecl uques ibr delivering a payload, hi addition or in dse alterative to a. tethered delivery system are also possible. For example, a UAV 2&0 could include an air-hag drop system or a a ehste dro system. Alternatively, UAV 200 carrying a payload could simpl land o the g ound at a delivery location. Other examples are also possible.

IV, iterative tl ^' AV Deploy merit Systems

fMSl | UAV systems may be implemente In order to provide various: IJAV-related services. In particular,, ϋ A Vs ma be provided at a .number of different lannch sites that may he in- eoaanunicaiion with regional asdVor eeetxai control sysleras. Such a disrrihuied UAV system may allow UAVs to be quickly deployed to provide services across a large geographic area (e.g., that is much larger than, me ni t ra»ge of any single UAV). For example, AVs capable of carrying payloads ¾f be d siriba¾d at a mtmber of launch sites across a large geographic area (possibly even throughout an satire coaittry, or even worldwide), hi order to provide on-demand transport of various items t locations .throughout the geographic area. Figure 3 is a sim lified block diagram IhiStraiin a distributed UAV system. 300, according to an exam le embodiment

0l.S2| In the illustrative OAY systera 300;, an: access system 302 may allow t¼ interaction with, control of, and/or utilization of & petwork of UAVs 304. in some embodiments, an. access system 302 may be- a eomputirtg system: that allows for human- corstrolled dispatch of UAVs 304, As such, the eoatrol system may include ^' or- otherwise provide a user interface through which a user can access arid/or control the UAVs 304.

fOlSSl In some embodiments, dispatch of the UAVs 304 may additionally or alternatively be accomplished via. orse or more Automate processes. For instance,, the access system 302 may dispatch one of ihe UAVs 304 to transport: a payload to a target location, and die OAY may autonomously navigate to the target location by utilizing, various on-board sensors, such as a GPS receiver and/or other various navigational sensors.

fQI f Further, the access -system 302 .may -provide- for .remote operation of a UAV. For isstauee, the access system 302 may allow an. operator to control the flight of a D AY via its u er interface. As a specific esarsiplc, art operator may use: die access system 302 to -dispatch a UAV 304 te a target location ^" The UAV 304 may then autonomousl navigate to the general area of the target location. At this poin ,, the operator aiay use the access system 302 to take control of the UAV 304 and navigate the UAV to the target location (o.g,, to a particular person to hom a payload is being transported . Other examples of remote operation of a UAY are also possible,

|0i5S| ht an illustrative euibotiinieut, the UAVs 304 xmy lake various .forms. For example, each of t e UAVs 304 may be a. UAV sneSi as those illustrated in Figures lA-iE. However, UAV system _; 300 ma also utilize other types of UAVs without departing from the scope of the inven iioti.. In some tmpiemmt iicnSi all of the UAVs 304 amy be of me same or a similar eoafiguratiori. However, in. other im lementations, the UAYs 304 may itKtude a number of different types of UAVs. Fo instance, the UAVs 304 may include a number of types of UAVs, with each, ^' type of UAV being configured for different: type or types of payload delivery capabilities.

|ΘΪ56 The UAV system.. 300 ma further ktelnde a remote device 306, which ma take various forms. Generally, the remote device 306 may he any device through which a direct or indirect equest to dispatch a UAV a be made. (Note tha an indirect request may involve arr comimstueaiioa. that may be ots^d to by dispatching a \ kV such as requesting a package delivery), ¾ as ^■ exa ple embodiment the remote device 306 iaay be a mobile ptione, tablet computer, laptop computer, pctsoriai computet, or any iteiwork- conneeted eojBj utteg device. Further, in some instances, the remote device 306 may not b a compu&Jg device. As an example, a standard telepnoae,. which allows for communication via plain old telephone service (POTS), may serve as (he remote device 306. Other types of remote devices are also possible.

1571 Further, die remote device 306 jrtay be configured to commmtiea e xvith access system. 302 via one or more types of e0mn¾mie tiofi. »et Qr¾s) 308. For example _* the i'emoie device 306 may eearatimcate witfe ihe aecess system 3€2 (or a hsma operator of the access system. 302) by communicating over & POTS network, a cellular network, and/or a data netwo k such as tbe Internet, Other types of networks may also be iro iaed,

plSSj In some embodiments, the remote device 30 may b configured to allow a user to reques delivery of one or more: items to a desired ioeatroji Far ex8mple _s a user could request UAV delivery of a package to their home via their mobile phone, tablet, or laptop. As attofjher example, a user could request %iia ie delivery to wherever the are located at th time of delivery. To provide suc dynamic delivery _* the UAV system 300 ma receive location: ½l¾rmation (e.g. _s GPS coordinates, etc.) fern the aser's mobile phone, or at other device oil rlie riser's person, suets that a tlAV eaa navigate to the user's loeatioii (as indicated fey their mobile phone);

|ftl.S9| _. In an illustrative rraugemeRt,. the central dispatch, system 310 may be a server or group f servers, which is configure to receive dispatch messages requests arid/or dispatch instructions from the access system 302, Sac dispatch messages may equest or instruct the eeoirai dispatch system 310 to coordinate the deployment of UAVs io various target iocatiofis. The centra! dispatc system. 310 may be farther configured- to fouie such requests or iastmciiorss to one or more local dispatch systems 31,2. To provide such functio iMy, the central dispatch system 310 may communicate witfe the access system 302 vi data network, siteh, as the internet or a private network that: is established for eommttsieatiotrs between access systems arid automated dispateli systems,

fO 0| hi the illustrated configuration, the centra! dispateli system; 310 may be configured to coordinate the dispatch of UAVs 304 from a nurnber of different local dispatch, systems 12, As such, the eeatral dispatch, system 310 may keep track of whiefi UAVs 304 are located at which local dispatch systems 31,2, whieh UAVs 30 are currently available for deployment, a»d or which services or operations each of the UAVs 304 is configured far (ia the event thai a O ^' AV fleet includes multiple types of OAVs configured for different services and/Or operations). Additionally or alternatively, each local dispatch system 312 may be configured: to track which of ts associated UA% 30.4 are currently available for deployment and/or are currently hi the midst of item fians oit.

j0:161| In some eases, when the central dispateh system 310 receives a request for llAV-related service (e,g., transport of an item) from, the access system 302, the central dis atch s stem 310 may select a specific UAV 304 to dispateh, e central dispatch system 10 may accordingly instruct the local dispatch system 312 that is associated with: the selected UAV to dispateh the selected ^" UAV ^' . ^r fhe local dispatch system 312. ma then - perale its associated deployment system 314 to lattuch the selected UAV, la other eases, the central dispatch syste 31 ma forward a request for a UAV^related service to a local dispatch system 312 that is near the location where the support is requested and leave the selection of a particular UAV ^' 304 fa the local dispatch system 312,.

(03:62] !R an example the local dispateh system 12 may be implenseaied: as a c nipetiii system.: at the satac loeatiori: as the deployment system s) 31 thai it controls- For example:, the local, dispatch system 312 ay h® k»plemented by eOtapnting systetn installed at a building _* . s«eh as a. warehouse, where the deployment systemCs} 314 and UAY(s) 304 that are associated with the .particular local dispatch system 312 are als located. In other etobodimeats, the local dispatch system 312 may be impSetttested at a location that is remote to its associated deployment systeai(s) 314 and UAYfe) 304.

[0163 f Numerous variations on and alternatives to the illustrated configuration of the

UAV system 30 are possible. For example, in some embodiments-,, a user of the r te; device 3 6 could request delivery of a package- directly from, the central dispatc system 310, To do so, an. application; may be implemented on the remote device 306 that allows the iiser to provide inibrraation regardin requested- celivery, and, generate and. send 3 data messag to request that die UAV systeiu 300 provide the delivery. In snch air embodiment, the central dispatch system 310 may Mclide automated fMBct oEaitt to handle requests that are generated by such. an. application, evaluate sneh re uests, and, if appropr te _* coordinate with an appropriate local dispatch system 31.2 to deploy a UAV,.

}0164| Further, some or all of the functionality that is attribu ted herein to the central dispateh system 310, the local dispatch systefn(s) 312, the access system 302, and/or the: deployment systemfs) 314 may be combined is a single systeni, implemented in a more complex system, aad or redistributed amon the central dispatch system 310, tkv local dispatc syste (s) 312, the access system 302, aod or the depieymeBi systemis) 314 ¾» various ways.

}0165| Yet further, while e ch local dispatch system 312 is shown: as having two associated: depJoyme systems 314, a given local dispatch system 312 may alternatively have more or fewer associaied deployment systems 314, Similarly, while the central dispatch system 310 is shown as being m commum ^' ca ioR with two local dispatch systems 312, the central dispatch system 310 may alternativel be in corammueation with more or fewer loca dispatc systems 312.

|0ί6δ to a forther aspect the- dspfoytaerii s stems 314 ma take various forms, la general, die deployment systems 314 may take the form of or hieiude systems for physically iattilchio orse or jjjOte- of the UAV 304. Saeh launch systems may include featpre that provide for as automated UAV launch and/or features that allow for a hxnmn-assisted UAV latineh. Further, the deployment systems 31 may each ^' be configured to launch -o . particular UAV 304, or to launch: multiple UAVs 304,

J <J7J The deployment systems 31 niay further fee configured to provide additional functions, Including; lor eMrople, diagnostk-ielated tectioRS such as verifying system, fonetionaii t of the UAY, verifying fonet Baii of devices that are housed within a UA V (e.g., a payload delivery apparatus), and/or maataiaing evise or other item that are housed ^' hi the UAV (e.g., lay niotutoriag a status of a payload. such as lis temperature, weight, etc.). |Μδ8| in some embodiments, the deployment systems 314 and their co**esporidinig- _.

UAVs 304 (and possibly associated local dispatch systems 312) may be strategically distributed throughout an area such as a city . Fo example, the deployment systems 314 may be strategically disnibuted such thai each deployment system 314 is: proximate to one or more payload pickup locatioas (e.g., near a resfeoraut, snore, or warehouse), However-, the deployment systems 314 (and possibly the local dispatch systems 312) m be distributed in other ways, depending up n the particular implemeMaiion, As an additional example:, kiosks 'that allow users to transport packages via UAVs may be Installed in various locations. Such kiosks a Include OA V launch systems _* and may allow a user to provide their package for loading onto U V and pay for OA.V shipping services, among other possibilities. Other example are also possible.

|0I | hi a further aspect, the UAV system 300 may irscl tide or have access to a user- account database 31 & The uset-aeeoniit database 31 $ niay include data for a sumoer of user aceoimis, and which arc each associated with one or more person. For a given user account. eoiiphng apparatus 412 front t!AV 400. The payload 08 may itself ¼ βα item fbf delivery, and amy be housed ^' wit in (or otherwise incorporate) a parcel, container, or other structure that is ^' configured to totcrfeee with the payload fetch 406, in practice, the payload delivery system 410 of IIAV 400 may inaction to autonomously lower payload 408 to the ground in a cOntrolled manner to facilitate delivery of the payload 408 on the gronud. while the DAY 40 hovers above.

{017 ! As shews: in Figure A, the payloa latch 406 m be in a close position(fc.g- _* piss engaging the payload coupling apparatus 413} to hold ώε payload 408 against or close to the b t m of the UAV 400, or even partially or eompicteiy inside Ilie tiAV 400,. during Sight i oni a launch site to a target losatiou 420. The target location 420 may be a point in space directly above a desired delivery location. Then, when tire UAV 400 re ches tire target location 420, the JAVs control system (e.g., the tether control module 216 of Figure 2). may toggle the payload latch 406 to an o n position (e,g,, isengaging the pins from the payload couplin apparatus 12), thereby allowing the payload 408 to he lowered from the IIAV 400, The control system ruay further operate the spool 40 (e.g;., b controlling the motor 222 of Figure 2} such that the payload 08, secured to the tether 402 by a payload coupling apparatus 412, is lowered to the ground, as shows is figure 48.

jOI7S| Once the payload 408 reaches the ground, the control system imy continue operating the spool 404 t lower the tether 402, causing over-run of the tether 402. During over-run of the tether 402, the puy!oad coupling apparatus 412 may continue to lower as th payload- 408 ema ns stationary en the. ground. The downward, momenrism: assl or gravitational forces on the payload coupling apparatus 412 .may cause the payload. 408 to detach fk»¾ the payload. coupling apparatus 412 (e.g., b shdihg off a hook of the payload coiipling apparatus 412). After releasing payload 408, the control system may operate the spool 40 to renuct the tedjer 402 mid die payload coupling apparatus 412 to ard the UAV ^* 400. Once the payload coupling apparatus reashes or aears the OAV 400, the contfol system may operate the spool 404 to pull the payload coupling apparatus 412 into the receptacle 414 and the control system may toggle the p ylo d latch 406 to the closed position, as sho u in Figure 4€.

0I76| Is some enihodimcats. when lowering the payload 08 from the UA V 400, the control system may detect whep the payload 08 and/or the payioad coupling apparatus 432 lias been towered, to be at or near the ground based on an. nnwoimd length of the tether 402 from the spool 404. Similar techniques may be used to determine when the pa ioad coupling apparatus 412 is at or near the UAV 400 when retracting the tether 402. As noted ahove, the UAV 400 ¾iay incl de an -e coder for providing data indicative of .t¾as rotation of the spool 404. Based on data, f om the encoder, fee eontrol system may determine how many rotations the spool 404 has nndergone nd, based on the nnmber of rotations, determine a length of the: tether 402 that is unwound frorn the spool 404. For instance, the control system rnay deiernitee an unwound, length of the tether 402 by Multiplying the number of rotations of the spool 404 by the eircuniiei¾nee of the tether 402 wrapped around th spool 404, In some embodiments, such as hen the spool 404 is narrow or when the tether 402 has a large diani ter, the circumference of the tether 402 on the spool 404 may -vary as the tether 402 winds or unwinds from the tether, and so the control system may ^: he configured to account fo these variations when determining the unwound tether length,

|!177| In other embodiments, the control system may use various types of data, and various techniques, to determine when the psyload 408 arid/or payioad cou ling apparatus 41:2 have lowered to h at o nea the ground. Furfter. the data that is used to determine when the payioad 408 is at or near the ground may h provided by sensors oft UAV 400 _» sensors on the payioad coupling apparatus 412. and or other data sources that provide data to the control system.

{0178 In some embodiments, the -caa-ttol system itself may be situated on the payioad eouphng apparatus 413 nd/or tm th OAV 400, For example, the payioad couplin apparatus 412 trsay tectnde gic; moduleCs) tmpien¾enied via hardware, software, and or firmware that cause the OAV 400 t function as described terete, and the UAV 400 may include logic rood«le(s.i thai eonlnmnieate wita the payioad couplin apparatus 412 to eans die UAV 400 to perfo m fettctons described herein,

|0179| Figure 5 A shows a perspective view of a payioad deliver,' apparatus 500 including payioad 51% according to an example embodimen The payioad delivery apparatus 500 is ositioned within a fuselage of a UA (not shown) and Includes a winch 314 powered by motor 512, and a tether 502 spooled onto winch 314. The tether 502 is attached to a payioad coupling apparatus 800 positioned widhn a payioad coupling apparatus receptacle 51S positioned: within the fuselage of ih& UAV (not shown). A payioad 51 is secured to the payioad eonpSIng apparatus 800. to this embodiment a top portion 513 of payioad 510 is secured within, the fuselage of the UAV, A locking is 570 is shown- extending through handle 511 attached to payioad 510 to positively secure the payioad beneath the UAV during high speed fligh .

J0180J Figure 5 is & cross-sec ionai side view of payioad delivery apparatus 500 and payioad 510 shown in Figtire 5 A. i this view, the payioad coupling apparatus is shown tightly "positioned wit the payioad coupling apparatus receptacle 516, Tether 502 extends ifotn wineh 51 a is attached to the lop of payioad -cotipliag apparatus 800. Top portion 513 of payioad 510: is shown positioned within the fttsclage of the UAV (aot shown) "along with handle S3 L

}0181| Figure 5C is a side view of payioad delivery apparatus 500 and payioad 510 shown k Figures 5 A and SB, The top portion 513 of pay load 5 0 is shown positioned within tte fitselage of the LAV. Winch 514 has been used to ind in tether 502 to position the payioad coiroling: apparatus within payioad. coupling apparatus receptacle 51.6. Figures 5 A~C disclose payioad 510 taking the shape of an astpdynaraie hexagonaUy-shaped tote, where the base and side walls are six-sided hexagons ^' mi. the tote includes generally pointed tent and rear surfaces formed at the intersections of the side walls -and base of the tote providing an aerodynamic shape.

VI» ExaKiple Ca siifes, Receptacle, a»id PackageTote

t&182| Figirre 6A is a perspective view of payioad coupling apparatus 8(H), according to _: an example embodiment Payioad eonpJiug apparatus 800 includes tether mounting point and a slot 8Θ to position a handle of a payioad handle in. Lower lip, or hook:, ·¾0 · is positioned, beneath slot :. Also Included fe an outer protrusion 804 having helical cant snrfeces .804a and 804b that are adapted to mal with corresponding cam roating surfaces within a . payioad coupling apparatus receptacle positioisad with a fuselage of a DAV, fl83| Figure 6B- is a side view of payioad coupling apparahis SO shown is. Figure

6A, Slot 808 is shown positioned above lewer!lp. or hook, 8 6. As shown lower lip or hook 806 has an outer surface 806a that is undercut suc that it does not extend as far outwardly as an outer snrfaee above slot 805 so that the lower lip or hook 806 will not reengage with the handle of the payioad after it has been cou le , or will sot get engaged wi th power lines or tree branches during .retrieval to die UAV,

[ 18 ! Figure 6C is front view of payioad coupling apparatus 8 shown i Figures 6 A and 68, Lower lip or book 806 is shown positioned beneath slot 808 that i adapted for securhig a handle of a payioad,

|01:$5 J Figure 7 is a perspective vie of payioad coupling apparatus 800 show In Fignres 6A-6C, prior to insertion into a payioad coupling apparatus receptacle 5 positioned in the fuselage 550 of a UAV, As noted previously payioad coupling apparatus 800 Includes a slot 808 positioned above lower lip or hook 806 _y adapted to receive a handle of payioad. The niselage 550 of the payioad delivery system 500 Includes a pa ioa*! coupling appamt»s receptacle 516 positioned, within the fuselage 550 of the UAV, The payioad -coupling _. receptacle is prevented. This scenario results in a revention, of ^' the. jaa«ning of die payioad eoupling apparatus w&hln the receptacle.

0 iB7 Figure 9 shows a perspective vie of a recessed resteaint slot arid payload. cou ling apparatus receptacle positioned in: a mseiage of a tiAV. Irs particular, payioad delivery system 500 includes a fuselage 5 SO vipg a payload coupling apparatus receptacle 516 therein that includes inward protrusion 530 having cammed surfaces 530a asd 5Mb ihat are adapted to mate with corresponding eaniroed surfaces m a payload eotrpliog apparatu (not shown). Also included: is a longitudinally extending recessed restrained slot 540 into which a top portioft of a payload is adapted to be ositioned: and secured widiin the fuselage 550.

0iS8| Figure 10A shows a side view of a payload delivery apparatus 500 with a handle 511 of payload 510 secured within a payload coupling apparatus 800 as the payioad 510.moves downwardly prior to touching down for delivery, Prierto payioad touciKlown, the ^' handle 511 of payload 510 includes a hole 513 through which a lower li or hook of payioad coupling apparatus 800 ext ds _* The handle sits within slot of th payload eoupliug apparatus 80£l that is suspended from tefher 502: of payload delive y system 500 during descent of the payload 1 to a lauding site.

l&lWi Figure lOB shows a side view ef payload delivery apparatus 500 after payload 510 has landed on the ground showing payload coupling apparatus 800 decoupled from handle 511 of payload: 510. Onee ihe payload 10 touches the ground, the payload coupling apparatus 800.continues to iukwe downwardly (as the winch further unwinds) through inertia or gravity and decouples the lower li or hook 808 of the payload coupling apparatus 800 from: handle 51 1 of payload 510, The payload coupling apparatus 800 remains: suspended from tether 502, and ear he winched back up to the payload coupling receptacle of the I V, fOlSOf Figure IOC shows a side view of p yl ad delivery appai atus 500 with payioad coupling apparatus 800 nioviag away from handle 511 of payioad. 519, Here the payioad coupling apparatus 800 is c mpletely separated, from, the hole 513 of handle 51 1 of payload 510. Tether 502 .raay be used to winch the payload coupling apparatus back to the payload coupling apparatus receptacle positioned is the fuselage of the OAV.

Θ1*>1| Figure 11 is a side view of handle 511 of payioad 510. The handle 511 includes a hole 513 through which tire lower lip or hook of a payload coupling apparatus extends through to suspend die payload during deli er :; The handle 51 1 includes a lower ortioH 515 .that is- secured to the top portion of a payload. Also ineiuded are holes 514 and 516 through which locking pins positioned, itte ! the fuselage of a U AV may extend to secure :the handle imi payioad a secure position dating high speed forward i!jg!it ie a deliv ry location. The handle limy be comprised of a fern, SfexiMe plastic material thai is flexible and provides snffieierit strength- to suspend fee payioad beneath a UA.V during forward flight to a deliver site, and during deli ery and/or retrieval of a payioad. In practice, die handle may be tot to position the handle within a slot of a pay load coupling apparatus. The liaadf SI I also has sufficient strength to withstand fee torqae during rotation of the psy!oad coupling apparatus into me desired orientation within fee payioad coupling apparatus receptacle; and rotation: of the top portion of the payioad Into position with the reeessed restraint slot

l&i I Figure 12 shows fr a of l cking pios 570, 572 extendin throug holes 514 ami 51 in handle 5.1 1 of payioad 510 to seesre the handle 51 1 and top portion of payioad. 510 within the fuselage of n UAV: in this ntmner, the ^' handle 511 and. payioad Sit) rnay fee secured -within the fuselage of a OAV, la this eriibodiment, the locking pins 570 and .572 have a conica shape so that they pull the package up slightly or a least remove any down rd, slack present. in some embodiments the Locking pins 570 and. 572 may completely ping the holes 514 and 516 of the handle 511 of payioad $ Ιίί, to provide a very secure atiaelaBent of the handle and top portion of the payioad within the fuselage of the UAY. A!feough. preferah!y the locking pins ate conical in other applications they may have other geonietries, such as a cylindrical geometry,

&Ϊ93 Figure 13A is a perspective vie of payioad coupling apparatus 900 prior to ving a handle of a. payioad positioned within slot 920 of payioad eoaplmg apparatus 900. Pa ioad coupling apparatus 900 has a tether slo 906 on inner sitrfaee 904 of portion 914 into which a tether 902 is inserted. Also included, is a pair of upwardly extending fingers 908 and 910 having a slot 91:2 posi tioned therebeweeiL A handle of a payioad may fee inserted into th slo 920 of payioad coupling apparatus 900 positioned be-tweer* upwardly extending fingers 90S and 910 and inner surface 904.

θϊ94| .Figure 138 is a perspective view of payioad coupling apparattis 900 after delivering a. payioad and decoupling the payioad couplin apparatus 900 from a handle of a payioad. In this embodiment, the upper portion of portion 14 is weighted such that when the payioad coupling apparatus 900 is decoupled from the handle of fee payioad _* fee payioad coupling apparatus 900 rotates I SO degrees suc that the fingers 908 and 910 are downwardly extending.; thereby preventing the slot 920 from reengaging wit the handle of the pay ioad, or engaging wife tree branches or wires dniing retrieval to the fuselage of the UAV, During rotation ollowfeg decoupling,, the tether 902 is pulled from the tether slot §06 (shown in :E a e 13 A) and passes throug slot 912 between fingers 908 arid 910 such that the pay load coupling apparatus 900 is suspended f oiii tetter 902.

j0i95f Figures 14A-E provide various views of pay ad coupling: apparatus 900 shown hi Figures 13A arid. 13:8; As shown in Figures M -E, the pay load coupling appaxatiis 900 includes a slot 920 positioned between apwardi extending fingers 908 and 91 and mam surface 904., A tetter slot 906 is positioned is ipnsx- sitrtace 904, A slot 91 also extends between upwardly extendin fingers 08 arid 910, A tether attachment point 922 is positioned eft a bottom of the payload coupiiKg apparatus 900. ^' The tether slot 90f> extends from iethetr attachment point 922 to the top of huier surface 904, Upper portion 914 of payload eoupling apparatus 914 is weighted, such that upo« payload lauding, the payload coupling apparates is automatically de oupled from the handle of the payload, and the weighted upper portion 914 eatises tie payload coupling apparatns 90 to rotate downwardly 180 degrees, Durin this period of rotation ,, a tether is pulled tr ee from tether slot 906 and the payload. coupling apparatus is suspended from the UAV via the tether attached: t tether attachment poin 922 with, fingers 90S and 910 pointing downwardly. As a result, the fingers 8 and 910 ate prevented froni reengaging the handle of the payload when retrieved to the UAV, and: also prevented frorn engagtag tree b aaeaes or power lines during retrieval to the UAV. Alt ougir riot.sho ft in Figures 14A-B, the payload eoupltug apparatus 900 co«M also iaciude esrnrned surfaces as showa. is payiea .c uplin apparatus 80 that engage with mating cams positioned within a payload coupl tag apparatus receptacle in the fuselage of UAV to orient the payload eoypliug apparatus ift a desired orientatio within: the payioad coupling apparatus receptacle,

fOiM! Payload eouplin apparatus 900 als advantageously is a solid state design that includes: no moving parts, thereby reducing the complexity and .cost of the payload coupling apparatus ami eliminating moving parts thai: eat* possibl Ml A more reliable payload. coupling apparatus is techy ovided,

|0i9?| .Figures 15Α-Β· provide various view of payload coupling .apparatus 1 00. h this enibod neot, payload eoupling apparatus 1.000 has a generall spherical shape.. A slot 1020 ts positioned bet een outer lip or hook 1010 and rounded portion 1014, The slot 1020 is 3d.aptcd o receive handle of a payload. A tether attac ment point 1022 is positioned on. rounded portion 1014. A tether slot I0Q6 extends from tether attach e poin 1022 to slot 1020 and is adapted to recei ve and hold a tether. Rounded portion 1014 or portion 1010 may be weighted such- that when a payload touches tte ground, the handle of the payload is decoupled from the slot of payload coupling apparatus 1000, During decoupling front the coupling apparatus f om snagging during descent M or retrieval to,- the fuselage of a UAV,

.{0203J The present embodiments provide a highly miegraied ^' wlriel*½scd .jpkkup and delivery system for l!AYs, A number of significant advantages .are provided. For example,, the ability to pick op. and kli ver packages wAont the .need for landing is provided, as the s s em Is able to winch u a package with the aircraft hovering. Although .in some locations, ioftasnitciure such as a platform or perch for landing or loading ihe OAV may be provided, in other location there may be m weed for infestmcture at - the merchant or -customer location. The advantages include high: mission flexibility and potentially little or no isfra^truetnfe installation costs, as well as increased flexibility in payload geometry.

f&204| is addition, the payload delivery system may automatically align, the top portion of the pay load during winch up _s orie»iing it for minimtim drag along the aircraft's longitudinal axis. This alignment enables high speed forward flight after pick up. The aM e t is accompli shed through the shape of the pay load hdofc and receptacle. In the payload. coupling apparatus 800, the lower li or book 8 6 has cam features around its periMeter which always orient it th. a defined directio when it engages into the -cam. features inside the reeepiaeie of the fuselage of the UAV. The tips of the cant shapes n both sides of the capsule ate asymnsctric to prevent janatnng in the 90 degree orientation, 1». this regard, helical ca surfaces ma meet at art apex on on side f the payload coupling mechanism, and lieiical cam sur aces ma meet at a rocuded apes on the other side of the payload coupling mechanism. The hook is speeiieaSly designed, so that the package hangs in the eemeriine of the hook _s enabling alignment in both directions from 9 degrees.

f0205J -Payload coupling apparatuses 8 CL 800', K , and 1000 include a hook forme about a slot such that hook also releases the payload passively and automatically when the payload touches die ground upon delivery. This is accomplished through tire shape and angle of the hook slot and die corresponding -handle- on the payload. The hook slides .off the handle easily when the payload touches down due to the mass of the capsule and also - ^' the inertia wasting to continue moving the capsule d nwa d past the payload. The end of the hook. Is designed to he recessed slightly front the body of the capsule, which prevents the hook from.: accidentally re-attaching to the handle _* After snecess&i release, the hook gets winched back u into ihe aircraft. All this functionalit (package alignment during pickup and passive release during delivery:): is achieved without an moving parts in this payload coupling apparatuses 800, 000, and 1000 (referre to as a solid state design). This greatly increases reliability and reduces cost hc simple design also Mates user i.Memcik>n very clear md selt-explaaatory,

VH. Teiher Coairoi Parin Payload Pickup

|028€| A UAV may be able to pick it md deli vet' a payload without landing* I» some examples, the U A, may be able to raise arid lower a payloa coupled to a tether by winding and unwinding the teiher while hoveriag. As such, the OAV pay pick up and deliver the payload. without requiring infrastructure be set up by a merchant or customer, the e y increasing a flexibility of delivery location atid or payload geometry arid decreasin or eliminadng costs associated with the manu&tu e or installation of inftasiraeiure. In..other examples, the. OAV may be eontlgnred to land on various elevated, sfnsctees, such as a perch or shelf, and, from its elevated landing. pos os. pick ttp or deliver the, payload by winding or unwinding the teiher.

|¾2I 7| Figure I 7 shows a method 1 TOO for tethered pickup of a payload (e.g, .. a package) for subseque t: delivery to a target location. Method 1701) amy be carried out by a UAV such as those described elsewhere herein For exam le _s method. 1700 may fee carried out by a control system of a OAV with a which system. Fatther, the winch system may inelude a tether disposed o» a spool, a motor operable & a first Mode and a second Mode that respectively counter md ^ m mi n^ of the tether due to gravity (e.g,. b fcivtog h spool forward or in Mvetsej _>; a payload couplhig apparaiws thai: raeehariieally couples the tether to a payload, and a payload latch switehable between a closed position thatpreYeats the payload from being lowered fmm the U A V and an open position that allows d¾ payload to be lowered f om the UAV,

[0208 J As shown by block 1702 of method .1700, when the UAV arrives at a picku location (also tererred to: as a utes location), the AV's control system ma open the payload latch, such that the tether and die payload coupling apparatus ats be lowered toward the ground at the pickup l cation

|02i9| At block 1,704, the control system operates the motor to wnwiftd a predefefinined lengt of the tether. This unwoun length may correspond to an expected payload attachment altitude for the payload coupling apparatus, which is attached to the lower en of the tether. The payload attaefement sltimde may be as altitude at which a kuma», or perhaps a robotic device, ma grab the payload coupling apparatus for attacMrig the coupling apparatus t a payload. For iustaaee ₅ the payload attachment altitude m be an altitude less -than two meters above gfonnd level Other examples are possihle as well. After .u& ind&ig the predefern¾tedl length of the tether, the control system may wait fee a predefermiped payload attaehraent period, as sfcrwn by block 1706. T & attachment period allows time for a human, or perhaps a robotic device, to attach a payload: (e.g., a package for delivery) to the paylQad eoupllng apparatus. The predeiermised payload attachment period m y be a fixed value or may vary based on an operational, state of the

I;AV.

receptacle, in particular, feea the calculated anwousul lengt of tether ½ at or near zero, this may radieaie that the pay load coupling apparatus and/or the payload have beett Silled ail the way to the AV. ¾rt¾sr when the r^ lo d co«|jKsg apparatus aftd/or the payload contact the UAV's receptacle area,, th motor entreat may increase as the motor's speed controller attempts to coMinue pulling the payload upward. A» _$ eoasiderlng both these indications,, the control system may avoid false positives.

|0 i5§ Thus, upon detecting both of the above-described indications, the control system may respo sively operate the motor in the first mode to put the payload into, at¾d orient the payload within, the receptacle on the lower surface of the UAV, as shown by block 1716. in pattie iar, the control system may operate the s - tbt to increase the t rque; applied to the tetlier, such, as by increasing die current supplied, to the motor to a predetermined value, iti order to help ensure that the payload coupling apparatus (arid perhaps the payload as well) are firmly seated against the corresponding surfaces of the UAV's receptacle,, such that die payload. laieh (e.g, _< pins 579 and 573 of Figure 13) ea * be closed to secure the payload for flight to the target iocatioji Accordingly, after applying torque to the tether hv att upward direetioii for predetermined period of time, the control system may close the payload latch, as shown fey block 17! ¾ With the payload secwed for flight, the UAV tnay navigate to a. target location tor delivery.

VOL Tether ont ol Biir o Fayl ad Delivery

&2161 Once die UAV arrives at the target location for delivery,, the tJAV's eositfoi system ma responsivety operate in a delivery mode. Figure 18 is a flow chart rltiistratirig a method 1800 for operation of a UAV in delivery mode, according to m example embodiment,

f0217f More speeittcally, once the UAV arrives at and is hover sag over a target location lor tet ered delivery, the ^■ UAV's control system amy operate the motor to unwind the tether according to s predetermin descent profile, as shown by block 1802, Th predetermined descent profile rsray control a descent rate of the payload by specif irtg a desired rotational speed of the .motor. For example, the descent profile may specify a constant: descent rate or a variable descent rate for the dMafioa .of the payload descent.

[02f8{ in some examples, the desired rotational motor speeds specified by the predeiermined descent profile could be based on .machine-learned data that conld be inferred from data from prior flights. For example, for deli .very to a particular kieation die. control system could use a descent profile that was previously used, d ing a previous deiivery to th particular location. Alternatively, If use of the deseent profile during previous delivery to that particular location or sett; ^■ ■ other location resulted is one or more delected errors (C.g., failure to detach .the payfoad from rae teiSief, daaiaged payload, etc.), itei the control sysiem. couid alter the descent profile ie,g, _: , by increasing or decreasing the desired motor speeds durkg various phases of the payload deseerst) or choose to use a default descent profile insiead.

|9219| la an. example method, the control system ma not exert significant control over the descen of the payload until it is closer to the ground. For instance, at some _: point while the tether i$ unwinding, the control system may determine that the unwound length of ike tether is greater dian a threshold length, and resppusively operate in a pre- touchdown mode, as shown by "block ί Μ. The threshold length .may con'espon.d to a. predetermined, near-grouud altitude of the payload; e,g., a height where more control is desirable for the safety of bystanders and/or ground struc tures, aud or to protect the payload and its contents from damage,

p228f As noted,, in the pi¾-to«ciidovm mode,, the control systeni may pay close attention to the payload to improve the chances of successful release of the payload on the ground. In particular, &ile operating in tae pre-touehdowii mode, the control system.: operates the motor such that the tether continues to unwind acc¾rcBag. » ¾. redetermined ^' descent profile, as shown by block I&tMa, white moustortug. both motor etrrreut and motor speed, as shows by block 1804b. The motor current may be compared to a predetermined pa load-uaeouipi g current to: delect when the motor current is less than the predetermined pay!oa l-useonpltng correal Additi nall ;, the motor speed may be compared to a predetermitted payload-uncoupMng speed to detect when the motor speed is less than the predetermi!ied pay3oad«-nuconpliug speed, as shown by block 1804c. When both the motor curreut is less than a predetermined payload-t¾coupIing current and the motor speed is less than a predetermined pa)½ad"oncoupiiisg speed, the couiiol system responsivei switches to operation in a possible-touchdown mode.

[022.1 J The possible-touchdown mode may be implemented in an effort to verify that die package has, in feet, reached the ground (or put another way, to help prevent false positive detection of contact with the ground). For instance, whi le operating in the possible- touchdown mode, the control system may analyze me motor current to verify that the motor current remains below the predetermined payloadmncoupling curreut for a iouchdowtt- veritleaiion period (e.g., perhaps allowing for a small amo«nt of fluctuation, dnring thi period), as shown b block 1806. hi practice:, a Schmitt trigger ma be applied t verit that die detected drop is motor curreut to belo the ayload-ancoupling threshold is not the result of o mme temporary blockage, and is in. fact due to the payload resting on the ground. Other techniques ibr verifying touchdown of the payload are also possible.

J0222 Once touchdown of the payload is verified, t e control- system operates the motor such that over-ran of the tether nd payload coupling apparatus occurs, as shown by block 1808. Qvet-rriB: occurs when the payload comes t a rest w ile ik tether eont iues to unwind. In practice, for example, the control . system, -may switch the wlac motor from the first mode to the second mode fey, e.g., reversing the direction .the motor and thus the direction, of torque applied to the tether by d e motor. Thus, ihe motor may switch from slowing the descent of the tether io forcing th tether to unwind sue tha overrun of the tether occurs. The over-run. of the tether amy in tyro lower the payload coiipling apparatus below a height -where coupling -to tile payload occurs (and perhaps ail the way t the ground)-. In. other embodiments, block li¾)8 may involve the control system simply taming the motor off, attd allowing gravity to pal! the payload coupling apparatus down and cause the tether over-run.

[0223| Further,, as shown in Figures &A-6 ^' C _S 1OA-I0C, and 1 1 , the payload and/or payload coupling apparatus ma tev irjierfaciag surfaces such that, the interaction, of the payload and payload coupling apparatus dtsring over-run deflec : the payload coapliag apparatus to the side of the payload. As such, th cou l ng eatu e of the payload coupling, apparatus (e.g , a hook) will no longer ^' fee -aligned with a corresponding; coupling, feature: of the payload (e,g,, a handle on a tote package). Located as such, the winch system ma retract the tether nd payioad coupling apparatus to the tlAV imOuf die payload coupling apparatus re-coupling to the payload, thereby leaving the package on the ground,

f0224| In some examples pi method. 1¾ίΚί, the control system may be configured to, prior to openiag the payload latch, operating die motor to apply art upward force on the- tether. This nmy allow for me pay load latch te be o ened m m easily., as dre pay ioad ma be arranged to rest some or all of its weight on the payloa latch when the latch is in the closed position. The weight of die payload may increase- the fr ction against the payload lateh when attempting to switch the hitch to the open position. So lifting the payload a predetermined: amount may reduce occurrences of the payload latch getting stack in the closed position. Additionally _* ate opening the payload latch and before unwinding the tether, the control, system may be configured ^' io operate the motor to hold the tether in. a substantially eonstant position. This may allow the weight of the payload to pall the pay load downward and against the payload coupling apparatus, causing, the payload to become fenly seated in a coiiplirig nieclianism (e,g,, a hook) of the payload couplin apparatus. IX _* User 'Interaction and Feedback, via Central of Tether

}Θ225| lit practice, a user may internet with the disclosed wlneh system i various ways and for various .'.reasons. For instance, the user may interact with die winc system to .manually couple or decouple a payload to the tether via the paytoad coupling appafaias, such, as for payload delivery ur oses or for payload pickitp purposes. in doing so,: the user may app ly forces directly onto die tether and/or may apply forces to the tether via the pay l oad coupling apparatus., among other possibilities,. Moreover, such interaction with the winch sys tem ma effectively also amounts to an interaction wi th die UAV itself because the UAV could adjust its operation based pa those forces (e.g., the UAV m y engage in light stabiii¾aiioii thst accounts for those forces)..

|0226} When the user ioieraets with, tile disclosed winch system, ihe laser could encounter various challenges. For example, the ttser .slot; know how the interaction with the winch system may ultimately affect operation of the wiBc system end/or operatioB of the HAY, As a result the user could inadvertently damage the UAV and/or the winch system, hi another example, the user may not .know airy mtnre operations that the DAV and/or the winch system plan to carry out. As a result, the use? cohM inadvertently stop the UAV and/or the winch, system from eatiyiitg. out a planned epe atien. la yet another example, the tsser may wait the DAY and or the which, system to carry OBC a certain Operation, hwt may not have the tneans t control operation of the UAV Or of the winch system.- Other examples are possible as well.

ifi227| To hel resolve such challenges., the disclosed winch system may be

-configured, to control the: tether so as to eraet with and. provide feedback to a user. Specifically, the UAV's control system ma he equipped with, the capability to interpret direct or indirect user interactions with the tether, perhaps carrying out certain operations is response to the interpreted ^" interaetions. Abo, the UAV's control system mm be equipped with the capability to provide information to the user by manipulating the tether, perhap doing so in response to a user interaction with the tether .

J0228J Figure 19 illustrates a method 190 for facilitating control of the tether for purposes of interacting with and/or providing feedback to a user. As shown by block 1902 of method 1900, the UAV's control system may determine one or more operational parameters of a motor for a winc disposed in an aerial vehicle, the winch, including a te ther and a spoo l . Then, the control system may detect, in foe one or more operational parameters, an. operatioriai pattern of the motor that is indicative of aa intentional uset-interaettan with the tether, as shown by block 1904 of method l fX>, Based on the delected operational pattern of

4? ^• fiie motor that is iridieaiive of the iateational MSer-i&teraetiou with the tether, the control s stOT: i«ay deterrafle a motet response process, as shewn by block I9 6 of method 1900; And as shown by block I¾S of method U ti, the control system may then operate the motor m accordance with the determined motor response process.

i, B&tefmimttg Op&rttiami Par mefers meter

|022 } As noted above, iiie WAV's control system may determine one or more operational parameters of the motor, in practice, an opera tions! parameter of the motor ma be an measure of the motor's activity.: Although certain: operations! parameters are described; herein,, other opemhonai parameters _^ axe also possible itbout departing imm the scope of the res nt disclosure,

f 0:230| By- way of ^' examples, an operational, parameter of the motor may he e«rrent characteristics of the motor, such as a current level being provided to aild Of generated by the •motor over time or at a particular instance in time, among other possibilities. In another example _* an operational parameter of the motor may be speed characteristics of the motor, seek as a speed, of rotation of the motor's transmission assembly over time or at particular instance i time, among, other possibilities . In yet aaote ^* exam le, as operational par meter of the motor may be rotation characteristics dib& motor, such as an exten of rotation of the motor's transmission assembly over time, among other possibilities. Other examples are possible as well.

§2 J Generally, the control systetn ma determlae one or more operational parameters of the motor in various ways, For instance, the control system may receive., -from ^' one or more sensor® coup ed to motor, sensor cats indicative of operational parameters. Ones the control system receives the sensor data, the control system may then use the -.sensor data to determine and/or evaluate the operational parameters of the motor,

fO¾32J By way of example, a current sensor amy be coupled to die motor aod eoniigored to gciier te curren data indicative of a cu nt level being ff vaded to aiid dr generated, by the. motor. With, this arrangerrsest, the control system may receive current data from tire current seris r and may use tire refeeived current data as basis to determine earrent characteristics of the motor For instance, the control system, may use tire received current data, as basis to detemrme particular current level of the motor over a partienlar iimepertod. Q233i In a otber example,: a speed sensor may he coupled to the motor and configured to generate speed data indicative of speed of rotatio of the motor 's: transmission, sssemhly. With this arrangement, the control system may receive speed data from the speed sensor sod may use the received enrreot data as basi to dete ime speed characteristics of the

first rime period). Other eases arc possible as well. | 23S| Given -the above-described arrangement,, the control system detecting as operational pattern may teolve flie coMrol s stem detecting ^' various patterns aruorig one OF more determined pa ameters. By way of example .(and without limitation), the control system, detecting an operational pattern may involve the eofttrol system detecting afty combination of the following: a particular relative change of motor current, a particular rate ■of change of motor current, a particular motor current value, a particular sequence of motor eurreut values, a partailar relative change of motor speed, a. particular rate of change of motor speed, a particular motor speed value, a particular sequence of motor speed values, -a particular relative change of niotor rotatio , a particular ^' rate of change of motor rotation, a particular motor relation value, and/or a particular sequence of motor rotation, valises, among others.

|0239J In accordance wit the present discl sure, as noted, detecting aft operational pattern may specifically involve detecting an operational pattern of the motor that is indicative of an intentional user-inte action with the tetter. More specifically, wteu a user interacts with the tether in a particular manner, the motor may exhibit a . _. articular operational pattern. As such, established operational patterns: (eg., established via manual engineering Input) that the control system car* detect, may each correspond to a respective nset-iirte etieu with the tether. in this way, when the entral system detects a particular operational pattern, the control system, may effectivel detect a particular user-inter action with the tether. In practice, the control system may do so simply detecting the operational pattern, and. wlthonf there necessarily hei»g a logical indication Of a liser-in teraction ,

|0249J in some eases, however, the control, system may maintain or may otherwise refer to mapping data that maps each of a plurality of operational patterns of the moto each with a respective user«interaction. For example, the mappin data may snap a particular current level pattern with au indication of a user providing a particular downward force on ike tether. In practice,, the particular downward force may he a force that is applied. In a direction. substantially perpendicula to a ground, surface and/or may be a force that is applied in a direction that is at anoiher angle {e,g., 45 degrees) relative to the ground surface (e,g,, such as w&Bira user catches an oscillating tether and then, tugs on it at an angle), la- other example, the QMppfng data may map a particnlar speed level pattern wit aa indication of user Bioving the tether side to side at a particular rate. In praetiee^ sueh indications could each take on any feasible forms, sneh as the form of letters, numbers, aad/or logical Boolean, values, amon others Accordingly, when the control system detects a particular operational pattern, the corrtrol system may refer to the map ing data to defernrine the xis r-mtetaetion that is espeeitwiy mapped to thai pariicttlar operationatpatferr

02 1 § Meireo ier, different operational patterns may sometimes be indicative of the same yser-interaecion. For this reason, ike control system may be arranged to detect a first operational patters and. thns effectively detect a particular user-interaction with the tethe * and may aiso be arranged to detect a second operational pattern and tints eftectivet detect the same particular aser-iateraciion with the tether, such as tor purposes of deterniining a motor response process as farthm- described belo . Alteraadvely, two or more operational patens in the mapping data could each, be mapped te the same itser-mteraction, so ^■ thai the control system detects the same yser-jnieraetion when tefen ^' ing to e ther one of those operational patterns in the mapping data. Other eases are possible as well

J02421 Yet further, when vasioas detectable eperatiorial patterns are established, at least some. of those established pattern could account, for various external- forces that may be applied to me tether., sitch as external forces other man just, those being applied by a. user dnriftg an interaction with the tether,. In particular, the operational patterns may account for gravity, external farces based on weight of the pay load eonpfhlg apparatus, and or exteraal forces based on weight of eoiiple payioad (e.g,, _: a weight, of package to be shipped), among others. In this wa * the control system may be able to detect m operational attern of the motor that is exhibited when, such external forces are applied in combin ti n with external forces that are based on a aser- te etiori. Other extersa! forces are possible as well

|ίϊ2 3| In yet a further aspect in addition to or instead of the above-mentioned mapping data, the control system may use one or more other approaches to determine a user- interaction based on art operational pattern of the motor,

{02 4! & one ease, the eoatroi system ma carry out signal processing and/or analysis^ techniques to ete m ne ¹ value(s) arid or trend{s) of a signal (e.g., a signal representative of motor speed v lues) and to determine the ttsei^interaefion based, oft those valne(s) and/or trend(s) of the signal For instance, tire control system, ma ev aluate a se t of conditions of a sigimi s as to determine; whether or not all conditions within the set are determined to he true, if the control system. de ermines: that all conditions of the set are true, the eoatroi system, may determine that the signal corresponds to a particular user-interaction. Otherwise, the control system may evaluate another set of conditions so as to determine whether or not all conditions withia that other set are determined to be tarn, and so on, hi an example of this approach, the control system may determine whether or iot a slope of die signal is within a particular range of slopes and may determine whether of not a value of the signal exceeds a may iavdlve oue or mote ^' particular operations by the motor, such as application of one or more patttettiar torques onto the te&er tot sfeuee. Moreo er, a motor response process may be arranged so as to cause the which system t« interact with the user via th tether andtorto provide feedback to the riser via ifee tether,, among other possibilities,

}02 | in accordance with the present diseiositre, the control system may detertnine tite motor response process .in various ways. In one ease, the control system may have stored thereon or may otherwise fee c nfigured to refer to mapping data that maps a plurality of operatioRal patterns each with a respective motor response process. For instance, the mapping data may map a particular sequence of speed levels with: a motor response process involyi ig the motor applying: OBC or more paiiieola torques to wind the. tether. ½ stick the control system m determine the motor response process by refemng to the mapping data to determine the respecti ve motor response process that is Mapped io the detected operational pattern of the motor .

0250f |n another case, the control system may actually determine c particular user- iiiteraetioa with the tether that is indicated by the detected operational pattern, of the motor, saett as by referring to the above-described mapping data that maps -various operational patier s respectively t various respective user-interactions. Arid the control -system may theft use the determi ed particular seNhtejpaesiJisv as basis for deternrmtng the motor response process,

|02S1| More specifically, the control system may have stored thereon or may otherwise be configured t refer to mappin data that, maps a plurality of liser-inferaetmns each with a respective motor response process. For Instance, the mapping data may map a particular side to side movement of the tether by a user with a response process involving application of a pariieolar torque to unwind the tether for a particular duration. As such, the ■control, s ste ay determine the nio r res onse pr cess by referrfag to ie mappiag data to determioe the respective motor response process tha is mapped to the particular nser- iateraetiori, which, was origiualiy determined based, on the above-described mapping data that map various operational patterns^ to various respective user- teraetioss. C feer eases are also possible.

[Θ252 in a further aspect, i»- ad itioir to or instead of niappmg data, the control system may use one or more oilier approaches io determine a motor response process, f 02S31 in one- case _f the control system m$y carry out signal processing and/or analysis tecfasiqnes io detainine valuers) and/or trendis) of a signal {e.g., signal repteseutative of motor speed values}- and. to determine the motor response process based on those valne(s) aad Of tread(s of the signal For instance, the control system ma evaluate it set of co itioas of a signal .so- as to deterrrrine feether or aot all conditions withlri the set are determined to- be troc. If -the control system <tem¾rifcs that all conditions of tire set are true, the control system may determine that the sigaa! corresponds to a particular motor res oase process. Otherwise, ike control system may evaluate another set of coiidhiorss so as to determine whether or sot ail conditions idrin that other set are determined to be true, and so om In an example of this approach, the control system may determine whether or not the signal includes an Inflection point and may determine whether or not a valne of a local maxima of die signal exceeds a particular threshold value, And the eontroi system ma detenitsrie that the signal cor esportds to s partieufar motor response process if the control system determines both of these coadi iions to be true. Other examples are also possible. }0254) In aaother ease, tbe control system may carr o-ttt probability analysis tecbnfcpes to determine the motor response process, fo example, the- control -syst m ma determine - that a detected operational pattern does not precisely match one of the operational patterns of tbe mapping data and thus ma apply probability analysis to determine the operatibaal pattern of :t¾e iitapniK data to w kb the detected aperatioaal pattern matches with the highest likelihood. For instance, when detennlaing the match, the control system may determine a state of ibe environment sad/or of the DAV during wbieb the operational pattern is detected, and m&y use: the state of the environment aatl or of the UAV as art additional weighted factor for detematiing the Matching; operational pattern. In tiris way, once the control system determines tire matching operational pattern nsing the the probability analysis,, the control system may then determine the motor response proces based ø« the mapping data. Other cases aad examples are also possible.

|0255| & a system arranged as; described above, the motor response process may- involve various motor response operations, so.cne of which are described below, to practice, the control system may deien¼¾e ^' the- ftw-t&r- i¾spc¾s© process to include a single sneh. motor response operation or any feasible combination of these motor response operations. Assuming o or more mbtett response operations are determined to fee carried out, detetminiag the motor response process May also hwolve deternrlruog an order for carrying out motor response operations fe.g,, with some motor response operations possibly being repeated at various points throughout tbe order) and/or a respecti e dur tion for applying each moto respons eperatioa _? ¾ΗΜΗ¾. other possibilities. Generally, such an order arsd or durations may be determined based on various factors, such as based on the detected operational pattern of the motor for instance. Alternatively, such an. order and/or durations may e- sdfetetemed in accordance with established ti^jpisg data..

}02S6| in either esse, ^' Various possible otor response operations are described below. Although certain nlotot response operations are described, other motor response operations are possible as ell without departing from tl« scope of the , resent disclosure.

|02S7f in one example, a motor response operation may involve a particular countering operation that counters unwinding of the tether due to at least one external force applied to the tether. As part of such art operation, the control system may operate the motor to apply one or more particular counteracting torques that each counteract imwinding f the tether, and possibly apply each sio^teraetmg. to que;, fat a. r^j^ct v.e.4¾raiijo(».. Specifically,, each sneii counteracting torqne may he at a magnitude that is substantially the same as the external fercef i being applied and nia fee in direction that is effectively opposite to directio la which external ihree(s are applied, in this way, this response operation ma resist unwinding of the te ther dye to the external &rce(s) bein applied without neecssariy causing retraction of the tether back t the IJAV. in practice, a nser applying an extspiai force to the tether may essentially feel tha the tether cannot fee lowered any further. Moreover, as magnitude of such counteracting torques increases, the tension: of the tenher may increase as we l

02SS I» another c nrpie, a motor response- operation may involve a particular assistance operation that assists unwinding o the tether due t at least one external force applied to the tether. As part of such an operation, the control system may operate the motor to apply one or more particular assistive torque tha t eaeli assist unwinding of the tether,, and possibly apply each assistive torque for a respective duration. Specifically, each such assistive torque m y fee in a direction that is effectively- 'that same to direction in which externa! ibrce(s) are applied, and ftiay be of any .liasihle magnitude, its ibis way, the assistive ionpes may be used i eonibination with the sxiernaf foree(s). being applied so as to fnrther hel unwinding of the tether, in. practice, a user applying an. external force to the tether ma essentially feel that .manual nnwinilssg of the tether has been ntade easier due to lesser resistance to the nnwinding.

i&Z5H>\ hi yet another exampl * a motor response operation ma involve a pai icular retracting operation that retracts- the tethe against at least oae external force applied to the tether. As part of such an operation, the control system ma operate the motor to apply one or -more psriicnlar retracting torques that eaeh retract th tether against the external fer¾e{s},. and possibl apply each retracting torqne for a respective duration. Specifically, each such retracting torque may be at a magnitude that is larger than the external f reefs) being applied and may be & a direction that is effecti ely opposite to- direction which external feree{s) are applied. In th s way, this response Opera on may resist unwinding of the tether doe to the external ft>rce(s} being applied and in fact cause retraction of the tether back to the IJAV despit the external foreefs). In practice,- oser applying aft external force to Ike tether may essentially fed that the teifter is pulling: against the user to m extent that, tire tethe retracts even: as though the user applies the external force.

f026lf In yet another example, a motor response operation ma occur after application of an external force by a user rathsr tha during applicatio of an external force, by a user.. For instance,, a motor response operation may ijiv lve a tether movement operation that moves the tether In accordance with a particular tether movement profile after the external force is applied onto the tether. In practice, such a motor response operation ma allow for user feedback/iriteraetioo to be carried out even when a user no longer physicall interacts with the tether.

|Θ263| In this reg d ike control system could- detect an operational patter indicative of a particular eser interaction and then dete iine a motor response process that, is; to be carried out. after die particnlar user Interaction is complete. In particular,, the control system ma determine that the particular user iutetaotion is- complete by detecting yet another o e tional pattern of the motor that indicates s and/or may do tins in other ways. I either case _i; once the control system determines that the particular user interaction is eorraalefe.. the eeuo-o! system could men carry our the determined motor response process thai involves movement of the iether i accordance with particular tether movement profile.

0262J Generally, the- particular tetbe movement profile may take various forms and may be based on the operationai pattern indicative of the user-interaction. For instance, the tetber movement profile xm$ simply involve retractioij of the tether back to the UAV at a particular rate. In this instance, niovement of the tether in. accordance with this tether movement profile may occur based, on detecting an. operational pattern -that is indicative of tire user pullin down o the iether several eosseeMive times . Other instances and examples are possible as well.

[02€3f Figure 22 next illnstrates an exam le motor response process. As sho n* the control system determines that the above-described particula user-interaction 21 1ft corresponds to a motor response process 2200,. Specifically, the motor response process 220ft involves a connteriug operation that includes application of a connteririg tort ue. That countering torque may have a magnitude of ' TV* that is substantially the same as the magnitude ^' "Fl" of fee downward force feeing applied by the oser 210:8, Also _> thai eor itering tonpe may be in a dlreclioti that is effectively opposite to the direction of the down ar force- feeing applied by the user 2108. As sash, the control system may idtiniately operate: the ^■ motor of fee winch system 2106 to appl that cotuiiering torque as fee user 2108 applies fee do n ard force onto the tefeer. Other examples are also possible.

Cipemtfag the- Motor in Accordance wi the Determined Motor espome

Process

f 0-264 j As noted above, once a motor response process is determined, the control ystem ma then operate fee raot t in: accordance wife the determined motor respons process, speeiSeslly doing so b tmhssTOtiing to ίΐκτ motor one or more commands that instruct the motor to carry out certain operations in line wit!i fee response process. And as further rioted above, .fee control system a do so during arid t after a user-interaction., -depending on the motor response process that has been determined. Moreover, fee motor response process that is carried out may lead to various outconies in addition to the planned hiteraetiors feedfeaek with the user.

{0265J For example, fee motor response process ma correspond to one or more target tension forces being eneotitttered by the tcAer, Specifically, each target tension force m be one that is expected to fee experienced fey the tether when the mo tor applies a certain torque in accor&aaee -with the motor response process. As such, t&e control system operating the motor in accordance with fee determined response process may earrse one or more such target tension force to be encountered fay the tether .

| 266| In anothe example, the motor response process may correspond to one or more target tether movement being encountered by the tether. Specifically, each tar et tether movement may he one that is expected to fee experienced by the tether when the motor applies a certain torque in accordance wife fee motor response process. A such, fee oatrol system operating the motor in accordance wife the determine response process may cause one or more sneh target isfeer movements to ^' be eneomrtered by fee tether (e.g., a w ve pulse traveling through the iefeerk Other examples are also possible.

10267] Figure 23 next illustrates an esample motor response process in which the control system -operates- the moto to control tension- of the tether 2102 a$ the user 2108 grasps onto fee tether 2102, -such as during ie process of manually coupling a payload fo instance. Assuming that the tJAV 2100 substantially maintains its physical position in space while hovering, the control sy stem .may proportionally (eg., linearly) increase the torque of me moto in a winding direction as a downward force provided b the user 2108 .increases:,. and Vice versa. la this way, the tettsion of the tether 2102 -toay increase as the user 2108 palls fee tether 210 further down, and vice versa. Moreover, the control system may be conilgnred proportionally Increase the toiqae of the motor up to a ax mum torque, thereb .sa rating the tension of fee tether and ideaily preveotmg fee user 2108 from pulling the UA V 2100 down towards Ike gronnd.

|026Sf More specifically, at state 2302 of the motor response process, the control system operates the motor to appl a torepe hmm$ a magnitude ' t" to coajftteraci the magnitude "FP of fee force provided by the use?- 3108, thereby resulting in a first tension force heing encountered hy the tether 2102. Then, at state 230 of the motor respons process, the - control system operates the n ter to appl a torque having: a utagfnt ile " 2 ^1S that is target than "'ΤΓ" and do so to e trnieract fee force magnitude that s larger than "Ft", thereby resulting in the tether 2102 encountering a second tension force thai is larger than the first tension force. Finally, at state 2306 of the motor response process, tire control system operates the motor to apply ίοκ β having a magnitude " 3' ^! that is yet larger than "T2" and do so to counteract fee force magnitude ^* *F3 ^W that is yet larger than ΎΤ thereb resniting in the tether 2102 encountering a thir tension force that is yet larger than the second tension force.

j02 Figure 2 c illustrates an exam le motor response process in which the ^• coatroi system may operate the rnotot to vary fee ahtownt, and possibly the direction,; of the torqiie that is applied to the tether 2102 over time, specifically dpfeg §ό to enhance user- experience or to otter reasons. For Instance, fee control system may operate the motor to replicat the feel of detents or clicks as the user 2108 ulls down on the tether 2102, and/o to provide vibrational feedback (e.g., a wave pulse) via the tether 2102, among other possibilities.

JO270} Mote specifically,, .at state 2402 of the motor response process, fee control system operates the motor to appl an ^' assistive torque feat has a magnitude "TP and is in the same direction as the force provided by the user 21.08, thereby assisting the user 21:08 with un in in of the; tether .2102, Theft, during unwinding of the tether 102 at state 2404 of the motor response process, the control system operates the niotort© appl a eouatemc iig torque having: a magnitude "T2" to counteract the niag«itu: e "F2'' of the force provided by fee user 2 i08 _s thereby resulting hi a feel of a "detent" being experienced by the. user 2108. Finally , at state 2406 of the motor respons process, i z control system again operates the motor to apply an assistive torque, so as to continue assisting the user 21 8 with . unwinding of the: tefeer 2103. Specifically, this further assistive force is shown, as having a. magfetade: and being provided In the same direction as the force (having magnitude ^* '' 3") provided by the user 2108.

j0271| Figure 23 next iliusiiates- an- example- motor resp nse process is which the control system interprets the. ^' tiSer ^' 2.l ^' Qft*$ inter¾?tion. with the tether 2102 to determine that die user 2108's intention is to eaase the UAV 2100 and or the motor of the wineh system 2106 to carr out certain operations. Specifically, at state 250 of the motor response process, the control sysiero detects an operational pattern that indicates that the nser 1 OS prilled down -on- i e tether 102 at least three consecutive times wi th a force sohstantiaily having nmgnitude of " T', Upon detecting m . gesture by the user 2 08, the control, system ma interpret the gesture as a signal that a paylostj ^' has been properly decoupled: from tl» payloa^ couplin apparatus 2104 and thus thai il e UAV 21 Oil ma proceed with fnrther flight to a target destination. Generally, .to facilitate such gestures, users could be provided with a rnaraial or the tike listing the- various gestures that are interjsretab! by the disclosed system.

|02-72f More specifically _* as shews by state 2504 of fee motor response process,, the Control ^' sysiero responds to -the gesture by carrying .out a motor response proeess that involves operat og; the motor to apply a torqoe having a magnitude "T2" for u oses . f retracting the ieftjer . 102 back to fte UAV 2100, Moreover, the control system, does so once the user 2108 has com leted interaction- with the: tether 2102 and tfcus no -fonger applies e terna] foree(s) to the tether 2102. Finally, once the tether 2102 has been retracted, the OAV 2100 may then proceed with forward Sight to a target destination, as shown fey state 2506. Other examples are possible as well,

v. Ad itional Features of !J er Interaction i Feedhiiek

|0273j In a ftather aspect, the control system could consider other factors as basis for deterahniog a m tor response process., in practice, the control system may consider such factors .in addition to or instead of eonsfderatiori of ihe- detected o e ational pattern of the. motor as described above. Moreover, the control: system may c nstdor any feasible combination of these factors, possibl giving some factors more weight compared to others. { ^' 27 | In one case, the cotttrol sy stent ma consider a state of the environmen as basis for detemhniog a motor response, proeess. Specifically, the control system may recei ve, from one _. or more of the AV*S sensors (e.gv, image eaptare device), sensor dat representative of the UAV¾ state of the environment, such as of obstacles near the UAV,. among oilier possibilities, And the control system may hen determine the motor .response proeess based at least on that sensor data. Fo example, if tire -control system detects an obstacle within a threshold distance awa from the tether, the control system: may responsibly select a motor response process in -whic the tether encounters smaier target tether movements rather than larger target tether triovemenis,. thereby atternpttag to avoid eoHisKm with the obstacle.

fS\ In another ease, the control system may consider a tJAV's state of light as

¾aski r deteraiitiii¾ a motor response process. Specifically, the control system may receive, from a flight niaaagemeat system (e.g, _: , oa«fcoard the UAV and/or externa! to the OAV), flight dat r<^resentative of a state of flight of the UAV. which may Be the UAV's iight progress along a planned flight _. path, among o¾her possibilities. And the control system m y iten determine the motor response process teed at km on that flight data, For ex ple, if the control system determine that .the .WAV's flight progress is sipifleaRtly behind a plaaned. .schedule along the flight path, the control system ma tesponsiveiy select a motor response process in which, the motor begins retracting the tether to a certain extern, so as to indicate to a user that that- the UA¥ ^s s flight progress is significaatly behind theptso ed schedule. Other eases and ^' .exam les are possible as we ^' ll,

p276J 1« ye a further aspect, the control system may carry ont the disclosed method

1 90 conditioned upo a payload (e:g., the payload eoxipliag apparatus and/or a coupled payload) being at payload. altitude at which a aser-interaetion is expected. More specifically, the control system, roay deiermtnc a. payload altitude of the payload wl may make a determination that, the payload altitude is one at which a user ntetaetion is expected. Otree the control system makes that determfcafi n, me control system may then rssponsiveiy carry out the method such as when a aser-interaetion is actually detected for instance, |027?J Generally, the control, system may use various techaiques to determine the payload altitude. la one example, att altitude sensor may he coupled to the payload. (e.g., to the payload coupiiag apparatus) aa the control sensor aisay receive, from tire altitude sensor, altitude -data indicati ve of the payload altitude. In another example, the control system tij y deternime an nawoirnd length of the tether, such as by asing techniques described hereia for instance. Also, the control system may determiae a flight altitude based on a mde data received from ah altitude; seesor of die UAV, among other possibilities, Then, the control system, may ase the -determined aawoaud tether length of the tetter as well as the determined ^' flight altitude as: basis for determiniag the payload altitude. For example, the control system, may subtract the determined unwound tether length of tlie tether ;{e.g., 5 .feet) from the determined, flight altitude (e.g., ίΐ feet abo e: ground) so as to d termine the payload altitude (e.g., ^' 6: feet above ground). [ 278 Moreover, the control .system may take vadoas approaches for deter»iai-»g that the payload altitude is o«e at which a user-interaction: is expected, .Per ursiatiee, the control system may determine that the pay ^' foail altitude is less t an a threshold aliit»de (e,g., established via ataaual engineering iaput). Irs practice, the threshold ahitiide may be a height above gr und at which osers eatt feasibly reach tile payload and thus iaterac with .the tetter.. Other iastances are possible as well

|Θ27 In yet a further aspect, the centrol systern ma operate the UAV itself :® accordance with a 1) A response process, which may involve at least a particular mo ement of the UAV, lis. practice, the particular moveraent could take o» any feasible forms. For e^arnple, the particular raovetweni m y involve side to _: side »ove«)eiit of the DAV along an axis in physical space.. In another example, the particular .movement ma involve iaitLliion of forward flight along a flight path, as shown. b state 2506 of Figure 25 for instance. Other examples are possibte as well.

;2 | Generally,; the control system may operate the UAV in. accordance with the UAV response process in additioa to or instead of operating the motor in accordance with a deteruhne mofot respotise process. & if the control systeru does so in additioa to operatin the .taoior in accordance with a motor response process, the control syste raay operate the motor and the UAV, respectively, to carry out those processes simil aneoasl aaife at different times. Moreover, th control system may perate the UAV i . accordance with the OA.V response process after andVpr dMing a aser- iieraetiorj.

( ^' 181 Vet fwrther, th t i systera may cfeiermiue the U V response process bas&I oa various factors . In doing so, the control sysiem may consider any feasible combination of those factors, possibly giving more weight t some factors compared to others, Nonetheless, various factors are possible.

282J. lit ne example, die eontioi system may determine the UAV response process based on a detected, operationa pattern of the motor. Wot i stance _: , the control system may have stored thereon or may otherwise he configured to refe to mapping data that maps a p arality of operational patteras each with a respective UAV response process. For instance, the mappin data may map particular secpeace of current levels with a UAV response process inve-lvmg the operating the UA to iit by a certain extent and in. a certain direction. As such, the control system aia determiae the UAV response process by .referring to the mapping data to determine the res pective UAV .response process that is mapped to the detected opcratiotialpattcrri of the motor. ία another exatt¾>k _s the coutrel system May determine the UAV response on a state of the UAV ¾ envlronBient and/or based on the UAV ¾ state of flight if die -control system determines hat the UAV ^* s state of flight iirvolves the UAV hovering over a first location on th ground and thai the state of the UAV's enykonmeot includes a aser physically pointing to second location on the ground, then the lAV response process may involve the UAV flying hover flight so as to end up hovering over the second location, such as for ptn oses of delivering a payload at the sscomd location, for instance. Other esanipies and aspects are possible as well.

(028 3 h is noted that the ahove-deserihed feature relate io er luteractipHi'fccdljaek are not litniiedto a situat n in which the UAV is hovering an could h carried out, io various situations- without -departing, from the scope of the present disclosure. For example, the various features may be carried out iri a sifnat eu in which the tlAV has laRded OR a ledge and the tether has beet* at. least, partially unwound such that the tether is suspended by the UA over an edge of the ledge _* Other examples are possible as well

Post-Oeliyery Tether Control

» Release erification

0285| As noted b e;, when & UAV la ers a payload to ¾e g oypd by eoatroiimg a motor to unwind a tether coupled to the payload, the control system of the UAV rrsay monitor the current of the rnotor and/or the rotati«s of fee spool to verif that the payload lias reached the ground. he contest system may then operate the motor to eaese over-run of ^" the tether by continuing to inlwiod: the tether fern die spool.. Once the touchdown of the payload is verified and tether overru is performed, t¾e control system, may operate iri a release- verification mode in order to verif separation of the payload from the payload coupling apparatus,, before feegimung the process of lifting the payioad coupling apparatus back to- the UAV.

}0286| Fi tsre 26 is. flow chart iiiystratuig release verification hiethod 2600, according to an example etnbodi merit. Method 2600 ^; may be initiated upon the completion of method |e,g,,, at the end of the tethe over -run period), as part of operation in th release-verification mode.

(0287J As shows, method 2600 involves the control system operating the motor m the first rsode (where torque is applied to counter the pull of gravity on th tether) fo a release- verification period, as shown hy hiocfc 2602. In practice;, the control system may apply a speed profile designed for release verification. The speed profile may be designed so as to lift the specific weight of the pa load coupling apparatus a small distance during the release- verification period Thus, if ^' the payioad has not been released, the motor will draw: more current to follow this speed profile, ttisa it does when the payioad has been properly released from the payioad eouplrog apparatus. Accordingly;, based at least in part on the motor current during the rolease-v-erifieaticiil period;, the control system may determoie thai the payload is separated feom. the payioad coupling apparatus, as shown b block 2604. For instance, the control system may determine that the- payload Is separated from, the payload coupling ap aratus by determining that the motor enrreoi: during <he reiease-verifeaiiori period is below a threshold current for at least a. threshold amount of time. A d, in response to this deteniHimt ps, the control system may operate th motor ta retract the tether, as shown by block 2«6.

0288 On the offset hand. If die motor :¾rreni dnrin the releasc-Yerifieadon period is large enough, then tile control system, may determine that the pay load has not been, separated from the payload coupling: apparatus, and may repeat the processes of operating the motor t cause over-feu of the tether (this time, perhaps, by some predetemhned additional length) and then pulling upwards 0» the tether to test for payioad separation,, shown, in blocks 1.808 and 2692 » 2606.

B, Tether Retrsctioa Processes

f Θ289 Once the release of (he payload: has been verified (e.g„ by performing method 2600), tlie control system ma switch to a rettaetion mode, in order: to retract the tether to lift the payload cowpiing apparatus back to the liAV.

|02¾r| In the retraction mode, the ascent of the payload coupling apparatus may be divided into two phases: an initial ascent arid a final ascent phase.

f 0291 During the initial ascent,, the control system ma uBpienient a predetenBhled ascent rate .profile, w eh may be designed -with the safety of bystanders and/or ab un ing structures lu i»ind. After die initial, ascent Is com ete (e.g., once a certain, iengtii of erser has been wound up), the control system may pause the retraction process, C g,,. by operating tlte. motor to mai ntain a substantiall constant length of unwound te ther.

|0292| Due to tire redaction in weight suspended fr m the tether (e g,, the weight of ike payload coupling apparatus only), tire payload coupling apparatus may be more seseeph e to swinging back and forth onee the payioad Is released. Accordingly, during the pause in tfe refraction process, the control svstsnr may evaluate whether the payload coupling apparatus is oscillating ^■■ (e.g., as a pendulum) and/o determine the magnitude of oscillations, and may e vai uate whether ac ti e¾s should be taken to dampen the oscillations. After or dining ■such damping processes, the control syste may initiate the final ascent of the payload coupling apparatus, in which t e tether retracts fis!Iy to pull the pay load coupling apparates to the UAV, and seat the payload coupling apparatus in ike UAV ¾ receptacle for the flight back to a return location,

}§:29S| More details regardi&g retraction of fee tether and: payload eoaphag apparatus after delivery are provided in reference to Figures 38A- C below.

XL Baiapi 8 sciik ioMS of a Payloati

0294| IB practice, ¾e UAV may sometimes encounter situatieas in which the tether is t feast partially un ound arid a suspended pay load eonpled to the tether is susceptible to oscillations. In one example of this sitttatiori, the UAV may deploy the tedier for delivery of a coupled paytoari, there y makin the efcupied payload susceptible to oscillations, in another exampl of this situation, the IJAV ma deploy the tether fo pickup of a payload, thereby making tbe payload coupling apparatus (e,g.. considered to be the payload la this ease) susceptible to oscillations.. In yet another example of this ^'■ situation, the iJAV may retract the tether tol!owuig couplin of ^' She payload or pickup, thereby making the coupled payload susceptible to oscillations. In yet another example of thi s sinsation, the UAV may retract the tether Mlo ing release, of the payload after delivery, thereby makin the psyload coupa ^' ag apparatus (e.g., again considered to be the payload in this ease) susceptible to oscillations. Other examples are also possible,

ff 29S Ιϊι such situations, va ions faeors may canse oscillations of the suspended payload. I» one example, suffieleGtiy steng wind con iiioas may cause the payload to oscillate. In another example, movement of tfee DAV to maintain its position in hover niode. amy cause the payload to oscillate. And. in yet another exa le, oscillations of the payload aiay be a result of an external force applied b a user to the teiher and/or the payload itself. Other examples are also possible.

[02961 ^' Generall , oscillation of the payl a may cause ike payload to -move back and forth Its a. pendulum-like nrotioa, also refee to as pendutar motion, la practice,, the pendular motion of an oscillating payload could have various consequences. For example, the pendubr motion of aa oseillatiag: payload may haye tmdesirahie effects on the stabil ity of the UAV, may create difficulties in positioning the payload in a desired location on the ground, may create an tsadesired mo vement of the payload near the ground, or may create difficulties ia seating tke payload coupling apparatus in the UAV's receptacle, among other problems, }¾297| To resolve these problems, the UAV's. control system may perform one or more damping techrjiques, snch as those described below. As noted above, such damping techniques may be performed after delivery of the payload,. dining pause in the tetker retraction process. However, ft should be understoo thai the below described damping tech i ues could: be applied oilier : scenarios as well Fnrther, datn tog tecfaaiijaes described herein eonht be applied in scenarios where &e payioad is still attacked to the pavload couplin apparatus (perhaps wit some- adjustments to account for the increase weight stispended from the tether, as compared to when only the payload conphsg apparatys is attached). More generally, damping ie.cliniq»es disclosed herein could apply in any scenario where a tether suspends a weight from an aerial vehicle.:

A, Dei eefion and EyaJaatKM* of Payload Oscillations

0298| in an. example implementatiors, a OAV may include ne or rrsofe sensors arranged to genemte sensor data indicative of oscillations of the pay load eoiajliog apparatus (aadior -of the- coupled payload) strspended belo the O A.V. hi pnactiee _s these sensors maynclude a currest sensor coupled to the wioeli aiotor, a tertsion sensor on the teiher. ail bieriial measurement -unit (JMU) on the IJAV and/or on the payioad coupling apparatus, an image capture device on the U AY, and/of m encoder on the winch motor, among odier possibilities. Accordingly, the UAV's control system mm <ise sensor data feam any combination of such sensors so as to detect oscillations of ije ayload as well as: attributes of the oscillations, such as a ijtMde, frequency, and or speed of oscillations, arnong other options,

|Ci29 f In one case _* the cu rent sensor may generate dat representative of electric current characteristics of the motor. The control system may receive such current data and rnay rise ate curren data as basis for detecting oscillation of the payload a well as for determining aftrih¾ies of those detected oscillations:: To do so, the control system could refer to mapping data or the like that maps various current characteristics, each with an indication of payload oscillations and'or with respective attributes of payload oseiUaiions. For example, a particular set of current charaeteristics (e.g., a. particular relative change in current value) m y be mapped t an indication ^'' thai the payload is oscillating. Also, anodier particular set of ^• current characteristic (e.g., a particular rate of change in current value) ma he mappe to an indication that the payioa is oscillating with a particular am htade of oscillation.

jOJOftf In antfther case, the tension sensor ma generate tension data representative of tension of the tether.. The control system may receive such tension data and may use the tension data as basis for detecting osciHariotis o the payload as well as for dctern ratig attributes of those detected oscillations. To do so:, the control system eouM refer to mapping, data or the like that maps various tether tension, characteristics each with an indication of payload oscillations and or with respective attributes of payioad oscillations. r exartiple _s a particular set of tether tension characteristics- : e.g., a. particular relative change in tension) niay be ma ped to an indication tte iljc payload is oscillating,. Also, another particular set: of tether tension, characteristics {e¾., a particular rate of change i» teasidt* may be mapped to indicatio fei&e payioad is oscillating wita a particular speed.

}CB0iJ in yet another case, the !MU may generate movement data indicative of movement of the payload. relative t the aerial vehicle. The control system may receive such movement data and may use the movement data as basis for detecting osciilatioas of the payload as well as for determmirfg attributes of ihose: detected oscillations. To do so*, the control system, could refer to mapping data or the like drat maps various characteristics of movement data each ¾·¾¾. n iadieahon of payioad oscillations and/or with respective attributes of payioad osciMatiohs. f r e^ra le, a particular set of movement dais eharaetemii.es miry he mapped to an indicatioB. ih¾ the payload is oscillating. Also, anothe ^■ particular set of movement data characteristics (e.g., movement data indicative of particular force) ma foe mapped to an indication thai the payload is oscillating, with & -particular atnpiiiude of oscillation,

f03ft2| f» yet another esse, tire image capture device may be arranged to face the payload and thus provide image data represetKativc: of position of tlte payioa relative to the UAV. With this arrangement, the control system may receive the image data and may ¾se any ew¾nt! known and/or fa m developed nmage processing techniques to evaluate the image data. In doing so, the control system may use the itnsge daia to determine position of the payload. over lime. More specifically, the control system may detect oscillation of the payload. by determining a difference in position of the payload over ime Moreover, the eontroi system could se the image data a basis for determining atirihotes of detected oscillations,. For example., the control system may determine a difference between certain payload positions over time and then determine amplitude of oscillatio based on the deteoniised. diilereace. In another eA mpfc, the control system amy use the image data io deteni e a rate of chang in position, of ihe payload and then determine speed of oscillation based on the determined rate of change. Other cases and examples are possible as well.

|0303J Moreover,, variotts attributes of payiond oscillations may depend on tie- extent to which the tether is unwound. For instance, a Shorter unwou d tether length may cause the payload to swing with a higher frequency eo pared to a frequenc widi w c the payload swings when the unwound tether length, is longer. For this reason, the control system may consider unwound tether length as an additional factor when detennining attxifonies of payload oscillations. For example, after determining that the tether is unwound at a particular fength. _!; the eonto! system ay determine positions of the payload Over time. "Then, the control system tmf relet to mapping data that im s the conmmatiou the determined taworiiid I gtk of the tether aud the determined position to a particular amplitude of oscillations asd to ¾ ^rtieuiar ¾¾ue»c - of oscillai ms.. Alternatively, the control system may determiue stteti attributes based oil a predetermined formula that inputs ^• variables, such the unwound tether .length and determined positions, and that ^' outputs data ndicative of one or more of the abo e-n eiUi oued atehuies. Other examples are also passible.

|03i | ,!«. practice, the control system -may determiue the unwound tether length by receiving fro the encode position data i jpTfcseutative of the unwound length of the tether. o e speclSeaily, the encoder may be _. -coupled o _. the motor suc that, as the motor carries out rotation to unwind and or wind the tether, the encoder generated data representative of an angular position andior mot on of the motor (e,g. _} of a transmission assembly of tire motor). As such, the control system may receive the data and may -use the data, as basis for tracking, tht- unwound length of the tether. For example _* the control system may detect two revokttioas of the motor in a particular direction based on the data from the encoder and ma determine that those two re voMioni eotrespoud to unwhiidiu Of the tether by two meters. Other exampl s are also possible,

ji OSf 1» a ftu her aspect, the control system; may also use the .sensor data as basis for detemnuiug the detected oscillations exceed a thresho C& , -established via manual engineering input}. For example _* the control system m determine that the sensor data is indicative of a particular aalplittide of die oscillations of the payl.oad, and wa detepnine- that the particular amplitude is higher than ihresho!d amplitude, hi another ex mp e, the control system that the senso data is indicative of a particular speed of the oscillations of the pay load, sneh as a speed at which the payload swings back and forth while the tether w partially unwound in this e antpie, die cant ^' toi system may then determine that this particular speed is higher than a threshold speed. In yet another example, the control system dun the sensor data is indicative of a particular freq ency of the oscillations of the paySoad. such a a frequency at w eh the payload. swings baefe and forth while the tether is partiall tar ound. in this example, the control system, may then determine mat this particular frequenc is higher than a threshold frequency. Other examples are possible as eSl

E, Damping d tiring a Tether Retract JOB Process

f§386f Figure 27 is a flowchart illustrating a method 2W0 fo initiating a damping routine (could also be referred to herein as a damping technique}, according to an example, embodiment. Method 270 ^; may be implemented, by a UAV's control system during a. tether retraction process. 1* practice,, t&e tether retraction proeess may be earned -Out -alter deliver and/ r at -other hraes during pick-up and/or e&!very. Moreover, aithdiig method 2700 is described as being carried oat its the context of a payload couplhig apparatus, method 2700: could also be carried out in the context of a payload coupled to the payload coupling apparatus.

|9307J Taming to method .270¾, the EJAV may initially he operating in a hover flight mode, as shown fey block 2702. For .instance* the UAV may hover over a target or delivery loca ion _; or over a source location. Once the- payload is released on the ground, the UAV's control, ystem ma switc to a tether retraction mo e^ as shown by Mock 2702. Whil operating, in. the tether re traction mode, the control system may perform a damping routine to dampen die oscillations of the payload eo¾pliag apparatus, as shown hy hlocfc 2704, Optionally., the- control system ma do -so specifically i response io deterrnifting that etec ted oseiTiations exceed a threshold

p308| Generally, ihe dampin routme that the control system performs may e any combination of the damping routines described herein. 1» some cases, however, the control system may per&rm one or more darnpirig rentine other those descrihed herein d do so ^• ithou departing from the scope of rriet od 2 00.

j#3 9J As-noted above, a damping routine, such as that perioraied at ock 2704, m be carried oat duritig pause in the ascent proeess (and perhaps during a pause while lowering the payload coupling apparatus as well), in sorne embodiments, the control system may wait un il die oscillations are . sufficientl dampened before resumin di proeess of retracting (or loweriug) the tedier. For example,, the control system may pause until it determines tha the amplitude of the oscillations is les than a threshold amplitude, of possibly even that, the payload coupling apparatus: Is resting in an c¾uilibriuru position. In eidier case, rise control s stem may respoasively resume retraction of ihe tether to Sift the payload. coupling apparatus to die UAV, in other embodiments, however,, the eontroi system ma sot wait until the oscillations are sufficiently dampeHed before resumis the process of retraeting (or lowering) ihe ther, For exam le, die control system might pause the tether retraction process for a fixed period of time before resuming. Specfficaliy, upon starting performance of the ^' damping routine, the control, system niay initiate a timer that is arranged to expire after a particular duration (e.g., established via manual engineering inpatj, and may resume the proeess of refracting (or lowering) die tether in response to detecting expiration of that timer. Other examples are also; possible. {0310} Figures 28A to 28D next collectivel illustrate initiation of a damping routine during ^" a tether mfmetiOn rocess.

03li| As shown b figure 2SA.,. a 1JAV 28CK) sncliiilss tether 2802 and a payioad coupling apparatus 2804 coupled to -the tether 2802.. Abo, a payioa 2806 is sho wn as haviiig been, delivered by the 13 AV 2860 at a delivery location on the ground. M reover* Figure 28A shows that the tlAV 2800 Is hovering over .he delivery location, while the UAV ^* s control system operates in the tether refraction mode so ascent die payioad coupling apparatus 280 back to the t) AV a ter .delivery of the payioad 2806.

03J.2| As showM by Figure 28B _:! while operating in die tother retraction mode, the tJAV's control s stem p sses the aseeat of the payioad eoiipliBg apparaius 2804. Sparing tlie pause, the control system performs a am ing routine, as indicated by Figure 28B, As noted, the dampin routine could be any of the damping routines described herein, among others. Qpitonaliy,. as noted, ^' i e control systeta performs the d mping routine h response to detecting thai Gscillations of the payioad coupling apparatus 280 are at an oseil dfi amplitude 2808 that is greater than a threshold, amplitude.

{ ^' 0313! As shown by Figure 28C, while the UAV's comtroJ. ^' system still pauses ascent of tli© payioad: coupling apparatus 2804, the oscillations axe shown to have been da peaed due to the daaiphig routine,. 1B one case, during the pause and after ^' carrying out of the damping rorrtine for some time period, the control system detects that oscillations of the payioad couplin apparates 2804 are at an OseiiSatioa amplitude 2810 that is lower thaa the threshold amplitude. I» this wa , the central system determ es that the oscillations have been sufficiently dampened and responsrveiy determines that: the tether retraction process ma resume, is another ease, the control sy stern detects expiration of a timer initiated upon starting performance of the dam in routine, md deterjnhies tot the tether retraction process .may resume in response to deieethig. eA h lfoa ot drat ilmer. As such, in either case, the control system may respoasiveiy resume operetlon t» the tether retraction mode to ascent .the payioad coupling apparatus 2804 hack to the UAY 2800 after delivery of die payioad, as shown by Figure 28 , Other illustrations are also possible.

C. Esatn ie ©sniping Teds aiques

{0314| Althoug several darppiag techni ues are described below, it shoul be understood that other damping techniques and niadifi cations to the described techniques are possible as well without departing fr m the scope of the present disclosure _^

Fo Wai i- FBgiit in IMmp Osei!fctttom [0315j Figure 2 is a flowchart ilktstrating a method 2900 for initiating for ard fiighi to dampen oscillations. As noted above, ike UAV may be configured to fly in accordance with a hove Sight mode and ia accordance with a forward ight mode, I hover flight mode, flight dynamics may be similar to a helicopter. Mote speeifkally, lift. arsd thrust m be supplied by rotors thai allow the IJAV to take off and laud vertically and fly in all directions, in forward flight mode, however, flight dynamics may be similar to an airplane. More specifically, a fixed-wing UAV may be propelled forward by thrust from ajet engine or a propeller, with fixed wings of the IJAV providing lifting and allowing the UAV to glide snhstaofiahy Ittizontaily relative to the grousid.

|0316 Willi tkis arrangement, the OAV may operate Jo acior acc with, hover flight mode, as sho n fay Mock 2902. As noted, the IJAV may do so {hiring a process of deploying the tether for pay load piekirp and/or for pay load delivery, or may do so during a process of retracting the tether for payload pickup and/or for payload delivery. Regardless, 'While, tire UAV is ifi the hover flight mode, the UAY's control system may caus trie UAV to switch ftoro the hover flight mode to the forward Hig , mode, as shown by block 2904,

317| Optionally, the control system may do s in response to determining that detected oscillations exceed a threshold. Also, the. payload at issue may be considered to he a.: payload (e.g., a package) that is coupled the payload couplmg spparatiis or mm be considered to be tire payload eowpliag apparatus itself among other possibilities,

|0318 More specifically, by switching to the forward flight mode, the movement of ike UAV ma result in drag on the payload. Generally, drag is considered to be: an aerodynamic force or friction dial opposes or resists an objee s motion through the air ^' due to interaction between the objeet and molecules of the air. So in a forward flight scenario;, airflow may result i» drag that is directed along direction opposite to the direction of the forward Oight. Thus, the .resulting drag may dampen lire detected oscillations of the payload because the airflow ma hel stabilise the payload,

10319| Furthermore, in some embodiments, when the control system causes the OAV to switch to the forward ^' flight mode, the control ystem m also direct the IJAV to operate in he forward fligh mode with certain flight characteristics, 1». practice, these flight characteristics may include Sight speed, light direction, and/or flight t »ti% _s among othe possibilities. As such, the control system may determiiie the appropriate flight characteristics based on various factors. Arid in accordance wU the present disclosure, the control system iiray deternnne the appropriate flight ciuiraeteristics. based at least on the detected oscillations of the payload andor based on other factors. [0320} By wa of example, the control system ma determine an initial flight speed for the forward fii ht mode based at least on the detected oscillations. 1B practice, the initial flight speed may be a flight speed to which die UAV Initially accelerates immediately idler switching to forward flight mode and one which the IIA.V ultimately maintains for a! least some time period dating the forward flight mode. So in accordance with the presen disclosure, the control system may determine an Initial flight speed that is generally higher when amplitude- of die detected oscillations is greater. For instance, the control system may ■select a first- initial flight speed when the control system detects a first amplitude of oscillation of the payload and may select a second initial flight speed when the control ystems detects a second amplitude of oscillation of die payload, w stir the first amplitude being higher than the second amplitude and the first initial light speed being higher than the seeond initial flight speed, Mote that the initial flight speed ma additionally or alternatively depend on mass, ηαάίόι dra of the payload, or may simply be predefined via m nual engineeri ng kgrcrt or the like

f 0321 J in another example _^ the control system ma determine flight timin for the forward fligh mode based at least on the defected oscillations _^ In particular, determining Sight timing may inv ^' olve deterrnlsing a time at which to initiate the forward flight mode, a ijra iott for which to carry e»f damping as part of the forward flight mode, and/or a tirne to end the forward: flight mode, among oilier possibilities, in either case, the control system may consider various factors related to the delected oscillations: as basis for determinin die flight timing. For instance, the control system .may determine state of the payload swing, such as whether the payload is at top of a swing or a. bottom of a swing, and ese that determined state of the payload swing as basis for determinin me flight timing. In another instance, the eontrol system m determine an - xte t, (e.g., amplitude) of payload oscillations and may deiertniae die flight timin based ø.·» die determined extent. Note that the flight timlrsg may alternativel be predefined via manual engineering input or the ^' like _* Other instances and examples are possible as well.

0322J In a further aspect, the control system may help facilitate th forward flight damping routine m various si&taiions. in one example situation, the control system may initiate .for ard Sight to dampen oscillations during a process of retractin the tether for payload pickup and/or for payload delivery, in this example situation, the control system eoiild technicall initiate the forward flight at any point of the retraction process, such, a without panse is the retraction process. Ideally, however, the control system may operale the motor to pause retraction of the tether while th detected oscillations exceed tlie threshold, which a allow the- control system Is? imitate, the forward flight mode diarag the. pause iu the retraction process, Then, once the ce-ritroi system detects that osciliatioiis of the payload have been sitfficiently danipefted- by the drag (e.g. _* thai the detected oscillations n longer exceed the threshold] aud/br after a fked time delay (e.g., i» response to detecting expiration of a timer), the control system may t efi operate the motor to resume retraction of the .either.

0323J In another example siteatioa. the control s stem may initiate -forward flight to dampen oscillations during a process of depl ymg the tether for pay load picku arid/or for payload delivery;. in this example situatkm, the control system could technically ini i t th forward flight at any point of the eplo ment process:, s¾ch as wit out a paase i.a the, deployment process. Ideally, however- tile control system may operate the motor t paase deployment of the tether while ifee detected oseiilatkirrs exceed the threshold, which may allo the control system to initiate the forward flight mode during the pause ta the deployment ptoeess. Then, once the control system detects that oscillations of the payload have been suffic ently dampened by the drag and/or after a feed tiftte delay (e ₍ g. _s in response to detecting expiration of a titrtef), the control system .may then operate the motor to esu e: deployment of the tether. Various other example u&tions are possible as well.

}#324| Yet farther _* , when the control system operates the motor to resum deployment or ie ractiott of die tether, the control system ma ideally do so while the UAV operates in the forward flight mode, het could also do so while the UAV operates n¾ the hover flight mode. (¾325J _. F example, once the control system detects that oscillations Of the payload have been sufflcleraly dampened by the drag and/or after a fixed time delay, the control system may responsively operate the motor to deploy or retract the tethe as the control system- also causes: the UAV to continue operating in the forward flight mode. Also, in the coutext of .retention for iastiince, the control system .may direct the t AV to mauiia s a particular forward Sight speed (e.g; _s the determined irntiat flight speed) as the tether is being retracted in this way _s the control system may easure safe and steady retraction of the tether. Tlien, once the control ystem- determines tha; that tether retraction is complete, the control system, may then responsively change (e,g,,. increase) the forward flight speed, i f applicable, Θ326| Additionally or alternatively, ¾tice the tether has bees fully retracted, the control system, could then cause the UAV to switch from the .fopvard fliglit mode back to the hover flight mode, hi -this' regard, after the IIAV switches back to the hover flight mode, the control system may then operate the motor to- deploy die tether. In this way, the forward flight may dampen oscillations of the payload. and subsequent hover flight ma allow for tethe deployBleut over a particular location, swefe as for payload pickup or delivery purposes. Other exarapies ate ftssibte as well,

_. {0327} in- a further aspect, the control system maf carr out ftsii!sod 290(5 conditioned upon the payload being at a safe distance a way from the UA.V . Generally, lie control system .may do so to eiisure that the payload does not collide wife the UAV upon initiation of forward flight and/or tm do so for oilier reasons. None&eiess,: the control system may -do so in various ways. For example, the control system may determine the unwound length of the tether and may then determine that the unwound length of the tether is higher thai) a threshold length, ibere&y indicating to the control system that the payload is at a relati ely safe distance away from the U ^' AV, in this way, if the control system seeks to catty out method 2900, the control system may do so only if the control system deterBMBes that the unwound length of the tether is higher than the threshold ieBgih. Other examples are also possible.

|8328J Figsres 3 A to 30D collectively illustrate the technique invOiv g forward flight to dampen oscill tions _* specifically doing so during a tether reti iction process.

p329| As shown by Figure 30A _S a t!A V 3000 inclndes tether 300 arid a payload coopling apparatus: 3004 coupled to the tether 3002. Also, a payload 3006 i shewn as having been delivered by the OAV 3006 at a delivery eation o the ground. Moreover, Figure 3 A shows that the U V 3000 is hoverin over the delivery location while the 0ΑΥ¼ eonteol system operates in fee tether retraction mode ¾} ascent the payload conpling apparatus 3004 back to the DAY atlct delivery of the payload 3006..

{033i}J As shown by ^' Ffgutfc 308, while the OAV 3000 is m hover flight .mode, the

UA.V's control system panses th ascent of the payload coupling apparatu 3004. Daring the panse. the control system ma optionally detect that an unwound IeBgih 3 10 of the tether 3Θ02 is greate than a tiireshQld length. Also, the: control system may optionally detest that the oscillations of line payload coupling apparatus 3004 ate at an oscillation amplitude 3008 that is greater than a mresho!d amplitude, Ίή s, regard,, the eonifni system may then responsively performs: the forward flight dampipg routine, as shown: by Kgnr 30/ In particular _!: w ile die tJ V's control system still pauses ascent of the payload coupling apparatus 00 , the UAV 3000 responsively switches from oper atag m hover flight mode to •operating in forward light mode, in other cases owe r the control system may not detect oscillations and may simply c m' out the forwar flight damping routing for a fixed period of time (e.g., until detecting expiration of a timer).

}0331) As show by Figwe. 3 C _f by switching to the forward flight mode, the movement of the UAV 3000 results in drag on the payload couplin apparatus 3004, which dampens fee oscillations of the pay load coupling apparatus 3094, Accordingly, during the pause and after the UAV carries out forward flight for some tlfee petted, the control system •detects- that osciiatiosis of fee pay load coaplmg apparatus 3ίί0 are at aft oscillauoa amplitude 3012 that is lower than the threshold a ph ^' inde. In this way,, the eoMroi system determines- iliac the oscillations have hee suffieieMiy darftpened arid responsively determine that the tether retraction process may resume.

{033f| As s own, fey Figure 3 ϊ¾ in response t eter ining that the oscilla ions have feeeri srrffiejently dampened and/or in response to detecting expiradon of tim r, the control system, then- resumes operation m the tether retraction mode to a seem the pay½ad coupling apparatus 300 hack to the UA 3CK1) afier delivery of the pa load Moreover,, the control system is shown, to resume operation in. the tether retraction mode as the control system eo irraes directing the UAV 3000 to operate forward flight mode. Odier illustrations are: also possible,

it RMmiftg. an Extmt of Flight S ibi!iz t m to I mpm O iUifttom

f0333| fn accordance with an example irnpiementaiion, the UA may be operafele |» a position~ho mode in which the UAV substantially aifttains physical position & physical space dining hover flight. Generally, the UAV may do so b engagin in one or mors Sight .stabilization techniques e.g., vision^-based stabilization an i½r IMU-based stabilization) during hover flig t suc as sta ization teeluriqttes ihat are currefttly known and/or those developed in the future.

|<3334f Specifically, the AV may engage in flight stabilization along; feree dimensions in physical, space, so as io resist .movement of the IJAV along any one of those three -dimensions ami t us to help maintain, the iAV's. physical, position,. In- practice,, the three dimeasions at issue may he the yaw axis of the UAV, the pitch axis of the UAV, and fee roll axis of fee UA . Additionally or alternatively, fe three dimensions may include any. feasible h&nslational axis for fee UAV (e.g., an axis along which irans!ational movement o the UAV is possible). But the three dimensions-. -could also take on various other forms without departing ¾Ο«Ϊ fee scope f the preseu; disclosure,

f 0335| Figure 31 Is a flowchart iliustrahrtg a taethod 3100 for redtiekg an. extent (e.g., gains) -of flight stabiSizaiioft to dampen oscillations ("go limp" datn ng technique). As. .shown by block 3102 of method 311 ⁾ 0, fee UAV may operate in fee position-hoM mode. Here again,, the UA may do so during a process of deploying the tefeer tor payload pickup and/or &r payioa:d delivery,, or may do so during a process of retracing the tether for payload pickup and/or for payload delivery. Regardless, while fee UAV is in the position-hold mode, tire UAY's coatrol system may reduce as extent of flight .stabilization alon at least one. dimension, as shown by block; 31(34. Optionally, me e«6troI system may do so response to determining that detected oscillations exceed the aboVc^descdbe threshold. Also, as notfc& the pay load at Issue may he eoasMered to be a payload (e.g.-,- ¾ package) that is coupled the payload coupling apparatus or ma be considered to be ifee payload coupling apparatus itself., among other possibilities.

}Ct336§ Μθϊδ· speei&ealiy, the "go limp" damping tectak|u.e _; may involve the control system causing me UAV -to tedoee an extent af flight siaMhzation along at least one of the ¾t^ve-t»e«]fi&.a!e¾ ^• 0¾ ^, ^e-.dii¾ei}sii&ss _< By doing, so, the UAV tua then move ai ag that dimension C¾.g„ translattanai movement aior.g the axis) based oh application of external forces to the UAV. in practice, these external forces ma be a resalt of the oscillations of th payioad. d as these payload oscillations cause a»vement of the UAV along the at least one dittte si ii at iss«e, ener y ma dissipate sver time, thereby resulting in dampi of the detected oscillations due to this esiergy dissipahojJ,

|0337| !R accordance witfe the presen disclosure, the act of reducing an extent of

Sight si¾bi i^€ai-ai0«g-¾¾e ^' ai ^' IeasE one dimension may take various fbJtns,

Θ338 j lift one case*. .« «ci»g an extent, of fligla siahiti^iioa along the at least one dimension may take the form of completely elitn«M«*g"any torn- of stabilization, along mat dimension and thus allowing tire UAV to move along that dmiension strictl based on ap tieaiioa: of exteisal forces to the IJAY _^ For example, a swinging payload may apply an external feree to the UAV along a. particular axis due to the UAV reducing stabilisation aioag the parh ^' cular axis, tfteUAV may en up moving along the particular axis fey an amount that is based OH a magnitude of that externa! force. In this way, the swingin payload. aiay essentiall drag the UAV itself along the particular axis. Other examples are possible as well.

I&339J In another ease, ho ever, r ediscmg an extent of flight stafeUtzatioa along the at least, one dimension ma ia.ke the form of reducing ilie exten of stabilization aioug the at least one dimension by certain extern Specifically, the control system may allow the UAV to move along the at least one dimension based, on application of external, fbrees to the UAV, but do so only to a certain extent:. For exam le, th UAV may engage in flight siabilizadoD after detecting some extent of movement of the UAV along the at least one dimension relative to the above-mcjitioned physical position. Is this way, the control system may effectively allow some range of moveinent cf the UAV along the at least one dimension relative to itte physical position (e.g., up to a two meter iranslational overoeM of the UAV a!CKftg a partieute ^' axis m ^' each direction) _* tattsst thaa. the UAV attempting to asaitttaia the UAV ^* s physical position -by res sting aay ajoveiaeBt ^' of the UAV away from that physical position.

[03401 Moreover, the control system y consider variou factors when deierffiiniag the extent to which to reduce stabilization along the at least oae dimension. I as example imp leaieotatioa,; the control system may use the detected oscillations- as basis tor deternviniag a target extent of stabilization. In doing so, & control system may d.etetn¾ne a lesser target extent of stabilization when th aniplitnd of the detected- oscillations is greater, thereby allowing for greater movement of the- ¾V al ng the at least one dimension so a to help dissipate energy. And due to swefc-. -greater Movement of the UAV the higher amplitude oscillations may ultimately dampen. Other eases ami examples are also possible,

|03411 .Following redaction of flight stabilization along die at least one dimension, the control system, .ma detect that, oscillations of the pay load hav bwn suf cie»fly- dampened and/o may detect expiration of a tinier (e»g. _s initiated, at the start, of the "go limp ⁵ ' damping routine}, and may responsively cause the aerial vehicle to increase an -extent o flight slabilizaiioa along the at least one dirneasioa. In accordance with the present ch ^' selosure, such i crease of flight stabilisation eotsld take oa 'various iiarats:.

| 342| In one example, assuming that the control system cause the UAV to completely eliaimste any ibrta of s ahiJkahoa along that ditneasion, the conlioi system ma cause the UAV to completely activate staM&ation along; that daneasioa ra an attempt t fully maintain the UAV's physical position. I» another example, again assuming that the control system caused, the UAV to completely eliminate any form of stabilization along thai dimension, the control system may cause the UAV to increase aa extent of stabilization alon that dimension by effectivel allowing some range of movement of the UAV along the at least owe dimension relative to the physical position, its yet another example, assuming that the _. control system, caused the UAV to _. partial!? - educe the extent of stabilization along the at least one dimension, the control, system ma cause the UAV to increase the extent of stabilisation, alon that dimension. In this exam le, the eoatrol system ma canse the UAV to increase the extent of stahilixation (eg., to the same extent prior to the redaction), so as to ei&etively lessen the allowed range of movement Of the UA V along the at least one dimensio relative to- the physical position. Alternatively, the control system may cause the UAV to increase the extent of stabilization so as to completel activate- stabilization along that dltnea ioa in an atteaspt to fully maintain the UAV's physical position. Various other examples are possible as well smer, the control system may respoftsively cause the UAV to iscrease the exteat of Sight stafeiimstjofi along th at least one diraeas a. 1B this exatsple, ate the UAV ^' increases the extent of fiiglt siabilizatiou along the at least onedinjeftsion* the control system may then operate the motor to deploy or retract the tether. Oilier xam les, at¾ _; possible as well, |0346 Figures 32A. to 3 ^' 2H fiex.i. eeliectively Illustrate tibe "go linip" damping technique, specifically being carried o«t dwing a tether retraction process,

347| As shewa by Figure 32A _S: a 11 AY 3200 includes tether 3202 and a payload coupling apparatus 3204 coupled to the tether 0 . Also, a payload.320 i shown as havin been delivered by the UAY 3200 at a del ivery fecation oft ili gtonad . Moreover, Fi gpre 32 A .shows that: the UAV 3200 is hovering oy r the delivery location wh le the UAV's control sy stem operates in the {ether retraction mode to .ascent the pay load cettpling apparatus 3204 hack to the UAV after delivery of the payload .320 .. in this regard, the- UAV 3200 is sho n as being in a -position-held mode .1» which the UAV .3200 substantially maintains a. physical os io is physical space during hover Sight

0348| As show b Figure 32B _S while operating t e iether retraction mode, the

UAV's control system paeses the ascent, of the payload coupling apparatus 3204, During, the pause, the control system opOoaaily detects that osctliatioas: of the payload coupling apparatus.3204 are at oscillation amplitude J2 S that is greater ^■ than a threshold .amplitude, fesponsive to detecting oscillations in this taaaaer aod/of responsive to initiating a timet,, fe control system ihea perforins the above-described '"go ha¾j ^?? danipteg rouliae. I» particular, the- con rol system causes the U V to reduce an extent of flight stabilization along- at least one dimension. By doing- so, the UAY then moves along dial dimensioa based on application of external forces to the UAV, which, may dampen oscillations dae to energy dissipation. Such movement and energy dissipatioa. is illustrated by Figures 320 to 32E

f _. 03 9j More specifically, due to ted-uctiou ta die xtent of -flight stabilisation along, die dimcasiosL the swinging payload ^' eoiJphng apparatus 3204 drags the UAV 3200 in. a first direction along the dimension to a positioa that is at a distance 131 away from position "X,Y", ESS shown; by- Figure 32C. Subsequeatly, due to contimt reduction in the extciit of flight sta itxaiio along the dimension and due tq energy dissipation, the swinging payload coupling apparatus 3204 drags the DAY 3200 hi a second direction fe.g,, opposite to the first direction) alon die dinieasion to a position that is at a lesser distance D2 (e.g,, smaller than. 01 ) away front the physical position *¾ \ ss shown by Figiire 32D. Sabsequently, again, due to coptiniied redeetion m the extent Qf ^t¾ah ^!.¾»-aJ ¾-g ^' tl]iedii¾ensi i and du to ftirther energy dissipation, the swinging payload. coupling apparatus 3204 drags the UAV 3200 in the first direction along the dimension t a position that is at an even lesser distance D3 e.g., smalle than D2) away fo.a& ike -physical position: X _S ', as .s a by Figure 32B. Finally, again d«e to. eontinaed redaction iti the extent of flight stabilization along the dimension and due to yet farther e;ne%y dissipation, the swinging payload coupling apparatus 3204 drags the UAV 3200 in the second direction alon the dimension t a position that is at an even lesser distance D4 (e.g., smaller than 153) away from tfce physical position as shown by Figure 32F . this tna¾i»er, the UAV 3200 ma continue moving hack an forth along the dimension as energy continues dissipating.

|035SJ As next shown by Figure 32u, the oscillations are shown to have been dampened due to the "go limp" damping rotitine. Optionally, drang. the panse and after carrying out of the " o limp-' damping routine for some time period, the control system detects that oscillations of the: payload couplin apparatus 320 are at an oscillation amplitude 3210 tha is: lower than the thresheid. am litude, in practice, the control system may carry out such detection while flight stabilization is still reduced along the dimension and/or after the control system increased flight s abilisation along the dimension, Nonetheless, the control system determines that, the oscillations have feces sufficiently dampened and/or detects expiration of a timer, responstvefy determines that the tether refraction process may resnme. As such, the control system, ay responsivei esume operation in the tether retraction mode to asceat the payload coupling apparatus 3204 back to the DAY 3200 after delivery of th payioad, as shown b Figure 32H.. Other ilktstration are also possible;

M Umvinciing/Wimttftg Tether ϊϋ Detypm OseiiM s

{035-1$ In accordance with an exampls im lementation, the IjAY's control system may dampen oscillations of the payload by operating the motor to unwind and/or wind the- tether, OiSieb changing "tension on die tether. In doing so, lite control systeta may increase: and,w decrease the un ou : tether length and do so at various rates, which ma hel dissipate energ and thus ulti mately dampen the oscillations of th payload. in this manner, tire control system is provided with an add lonal control inpnt thai does not necessaril kter&re with the other control objectives of the system (e,g,, does not prevent, the vehicle from holding position while also damping payload oscillations)

f0352| More specifically, the control system may operate the motor to vary a retraction rate of the tethe and/or a deployment rate of the tether. In practice, the retraction rate may define timing,, extent, and/ or speed of tether retraction arid the deployment, rate may ^■ define timing,, extent, and/o speed of tether deployment. As such, the eotitrol system may ma operate i aioftf in the ^' -first mode to retract She tether at the at least mm target retraction rate (e.g., defe ed ^' based mi detected oscillations and/or establishe via manual engineering inpat). Additionally or alternatively., the control system may operate ^' the moto in fee second mode to deploy t e tether at the at least one target deployment rate (e.g., determined based on detected oscillations and' r established vi manual engineering input). With ^' this arrangernent, the control -system cmM thus use various specific approaches for d mping oseiOatiotss via control of the tether at various rates,

f03S3| For instance, the control syste x y control the windin and/or rmwindrng of the tether, or the rate of winding and/or iRiwi«dsBg ^: of the tether to "pump" the payload .much like, a swing,, with tether let out as the pay load moves toward the bottom of the swing. and fee tether held fast (or eve wound in) as tile payload moves towards fee tops of tire swing. Moreover, a " um ing" frequency, period, asd/or phase of the tether ma be respectively -matched, to an oscillation fiectuonc , period, aftd/or phase of the payload. By doing: this, the energy of the swinging payload. may be removed even as the HAY remains substantially stationary.

|03S | Furthermore, the extent of "rarmping" of tire winch may de end on the distance between tire payioad a» the UAV, winch corresponds _^ to die uftwo-und lengt of fee tether. Specifically., when there is large distance between the pay-load and the OA.¾. the pendulat motion of the payload ma he very slow, ott the order of ¼ hertz for instance- At this point, the aniOBnt of the tether unwoun or wound onto the which during ^ umpin " of the winch may be on the order of meters. But when the payload is- -closer to the t?A.V, the penduiar motion m y speed up to on the order of 1 hertz or more for instance. In this ease;, the anrount of the te ther unwound or wound onto, the winch, during '" ^' pumping ^{5 '} may he on the order of centimeters..

035S| Yet further, the rate of speed at which the tether is wotaid- or unwound may var from one period of oscillation to fee next as the distance of the payload to the UAV changes, and ma even/be varied withi a single period of oscillation. For example, the rate of winding or unwinding may be proportional ¾ the velocity of the payload or the velocity of the payload squared. Other examples ate possible as well,

f 356f With this arrangement fee control system ma "pnrop" the winch while operating in the tether .retraction mode to engage in ascent of the payload or while operating in fee tether deployment mode to engage in descent of the payload. Specifically, during deseeot of the payload, fee oscillations of the payload ma he damped by letting tether oat at as the payioad approaches the bottom of the swing. Whereas, when the payload is .moving towards the fop of the swin , tfee am atiit of te&er unwound from the -winch could be -reduced or stopped, or the tether mM even be woae in as t e payload moves to. the tops of the s ing. Such ' ^{^} wm ing" of the tether ί&ψ eoiaferaet. the pendalar tnotioa of the jjayloac to control and damp the oscillations of the pay!ead, In contrast, during ascent of tile payload,. the oscillations of the pay load ma be damped by winding the terhe iu as the payloa .moves to the tops of the swing. Whereas, when the payload: is moving towards the bor oni of the swfe _s . the tether eoald be unwound, or stopped, or w und & at {-educe rate. Other approaches arc possible as well.

iv. (M$ ^f M&vem i ¾f Dampen Qseiiiafwns

J0357 : in accordance with an exam le Implementation:, the WAV's control system may dampen- oscillations of the payload by dirsetmg the ^' XJAV itself to move la various ways throughout .physical space. With this approaeli, th& control system ma direct die UAV to reactiveiy mo e in a -manner that offsets, prevents, or reduces movement of the payload ^• daring ascent and/or descent of the payload. Althoug various sne movements are described below, other movements are possible as well without departing fern the scope of the present disclosure,

Θ358| More specifically, the control system may be opexaMe to detetnntse a target path, of the payload. Tins target path m he a target path of ascent: of the payload a ing winding of the tether or may he a target path of descend of the payload daring tHiw nding _: of the tether. For example, the target path may be substantially perpendiciiiar to the ground arid ma ex end fen), the ground to the: UAV. In this way, the eonfel. system ma effectively plan to niahitain the payload substantially beneath the OAV as the payload is be ng lowered or raised. Bat oscillations of the payload .may eanse the payload. to move away from the target path as die payload is being lowered or raised,

f03S { lb help solve this problem, as noted, die control s stem may- cause die UAV to move hi various ways, Specifically, at a given point in time, the control system ma ttse the detected oscillations of the payload as basis for determining a position, of the payload relative to the target path, Then, hissed on the determined position of die payload relative to the target path, the control system may determine a movement to he pertornted b the UAV so as to move the payload closer to tfce target path, and the eontrol system, may cause the DAY to perform that determined movement As such, the con rol system coidd repeatedly determine sqeli movements as position of the payload relati ve to the target path changes over time dae to oscillations, and co»ld repeatedly cause the UAV to perform the movements to help dampen the oscillations:. j 36#| By way of exam le, the pendn!ar motion of the paylead co uld be controlled by moving OF translating the tJAV hoti n l I» response to the motion of the payload, e.g, by attemptin to maifttair. the payioad beneath (he UAV. Oscillations o the payldad ffcg,, pendulum-like swinging) would he damped by havin the UAV translate ( .g., mo hack and fbrik) in such a way that the oscillations ate minimized. For Issiasee, Use contra! system ma determine .that a curfent position of die payioad is at a particular distance away .from the target path and that the payioad is cnrreRily moving in a particular direction relative to th target path. KespORsive!y, the control system may immediately cause the tlAV to horizontally move in the pariieiilar direc&m and do so by r amount that is based ok the partictsiar distaace _f thereby attempting to maaitain the payioad ¼rreath the DAY. in this manner, the control system may reactively determine horizontal movements that offset horizontal forces OR tile payioad, arid prevent ordamp the oscillation of the payioad. Other examples are possible as well.

P. Selection of Damping Tec tMipes

|036l j Pi s© 33 is a flowchart illustrating; a method 3300 for selecting .one- or more damping routines teeiariques to help dampen oscillations of the payioad. in practice, the UAV's control s stem could carr oat roeihodJSO ^Q while operating in tether refraction mode or while operating -in- tether deployment mode. In accordance with block 3302 of method 3300, while the: tether is at least partiatl unwound, the control system nar select one or more dajapia . tontines from a pluralit of available damping routines t dampen di oscillations of the p yio d. And the control s stem may then perform those selected- damping tontines,, as shown by block 3304,

Irs accordance with ie present disclosure, the control system tm select any one of the above-described damping routines. Specifically, the control system may select any ■combination of the Soilowmg .roy tines: forwa d ^' Eight to dampen oscillations, "go U p ^** technique to dampen oscillations,, winding/unwinding of tether to danrpen oscillations _* and/or UA.V movement to dampen oscillations, in ptaetiee, however _S: the control system could also select other damping routines that are not described herein and then perform sneh damping r uti es individually or in combination with any of the above-described damping raiwines:. f 3€3| Moreover, tire control system ma select tire damping routines based on. various factors, some of which are described fcelow. in practice, ike control system may use any combination of those factors as basis, for the selection, jjerhaps giving certain factors mote weight compared to others. A iOitgh example factors ate described below, other factors are possible -as- well without departing fern the scope of the present disclosure.

■m$y determine that the "go li p" dampin technique should be performed followed fey pe formin of the ¾twinding/winding of tether ⁵ damping technique. In this regard, the control system may determine that the second damp hm routine should begin immediately foiiowiag the ead of the. first dam ing rontiae. Alternatively, die eoatrot system ma determine that die control systera shoul wait for a particular lime, period after perfottniag me •first cing routine and then perform, the second damping routine u on expiration of the particular time period, la some cases, the eonirol ^' system may use the particular time period to evaluate the detected oscillation and may decide to: move forward with performing the second dam ing routine only if the oscillations haven't bees sufficiently daBlpened.

[0372 In another example ap ro chi. the control system may determine thai, the control system should concurrently perioral two or more selected damping routines. For instance;, the control system may determine that the control system should co.ne«rreutIy peil riij the UAV m vement danipuig technique and die unwiadiag/wiading of tether damping technique. this regard, the control system may determine iiiat the control system should: start performing the selected damping routines at the same point m ime. Alternatively:, the control system may determine that the control syste should start perforraing a irst damping routine and, in the midst of performing: mat first damping routine, begin performing a second damping routine. Other example approaches and eosnbinattons of the described approaches are possible as well,

E. Additional Damping Aspects

j ^' S3?3 Althougk. various damping ieeteicnies are described, herein as being carried out after or responsi ve to detecting oscillation, of a payload, the various damping technique may be carried out in other situations as well For instance, tire control s stem may be configured to carry out one or mere damping teel ique during certain phases of flight ahdfer dnriRg certain p&asfes of payload pieicup a d or delivery, among oilier possibilities. In this instance, the control system may carr out those dar ipirtg techniques without necessarily detecting oscillations of a payload. In this regard., as noted, the coiitrol system may catty out the damping routine for a eertais time period, such as by initiating a timer upon start of a damping rontine and. then ending the damping routine (and or carrying out Qther operations, secfc as resuming tether retraction) responsive t detecting expiration of that ti e^ In this manner, the control system, may essentially take preventative actions ίό minimize say oscillations that might he present

ll. Faitere Beteetfen m& Correction Methftds

A. Failure to Metease Payloa

}0374j As described above with respect to methods Ϊ800 and 2600, the UAV ma operate in a delivery mode to deliver a payload .fo-a- target k>cai¾ra -aad- subsequently op rate in a release- verification mode to veri.fj.' that the payload has separated from die payload coupling apparatus, ow yer _* : there may ^' be situadoris in which the - payioad does not separate from the payload eonpliag apparatus ttpoa delivery. For instance;, the pay-load coupling apparatus may become snagged on the payload suc that when the UAV motor is operated to cause over-run of the tether, the pay load coupling apparatus remains coupled to die payload talker than lowering asd detaching i¾tn ^' & payload. Accordingly, the control syste may detect such a situation and respoasively take remedial action by causing the tether to detac from the UAV rather than causing the payioad to detach from the payioad coupling apparatus,

f 0375J Figure; 34 is a flow chart illustrating a method 3400 for detaching a. lethcr from, a UAV, Method 340 may he carried out by a U V such as those described else uei¾ ercffi. For example _* method 3401) ma he earned out by control system of ^* a UAV wit winch system. Further, the winch system may ineinde a tether disposed on a spool a mote operable in u first: mo e and- a secon mode that respectivel comt!er and assist unwinding of the tether due to gravity ^' -{e.g.,, b driving the spool forward or i& reverse), a payload coupling apparatus that mcehanicaUy couples the tether to a payioad, and a payload latch switchab e between a closed position that prevents the payload from being lowered from the UAV and an open positio that alio ws the pay load to he lowered from the UAV.

f§3?6 ^" f As shows by block 3402, method 3400 involves the eomrol system of die:

UAV operating the motor to unwind die tether and lower die payload toward the ground (cg. by perrbrming metho .1800). The control system nia be configure to detect heu the payioad contacts the ground and res^onsiveiy initiate a tethe ever-rnn process to atiernpt to release the payioad from fire payioad coupling apparatus, as shown by block 3404, Tether o etr-tm occurs w¾eu the motor eoraln s to unwind the tether after the payioad has .stopped lowering- During tether over-run, the payioad coupling apparatus continues to fewer as the tetlre is .un.wo.tmd, while ihe payioad remains stationary. This can cause the payioad coupling .apparatus to detach from me payioad,. ^' for instance, he the payioad is resting, on a prot di g arm or other hook-like mechanism of the payioad eoiipling apparatus. As deserihed above with respect to method lite control system may detect when the payload contacts the ground by monitoring a speed and/or a - ent eat of the motor an determining that the ^■■ .motor speed and½" motor current is threshold low. As tnrther described above witli respect to riiethod 1.800, initiating the tether over-run process may involve operating the motor in the second mode to forward drive the spool in a direction that causes the tether to continue to un ind even atler the load has reached the ground,

f 37?J Typically, carrying oat the tether over-ran process wotdd eause the pay load coupling apparatus to detach from the payioad. However* in simaiions where the payioad does not release ftorn the payioad coupling apparatus, the tether over-run process ma be repeatahle up to a predetermined .nui»berOf times, as fttrmer shown b block 3404,

j¾3?8I I» practice, once the payioad has reached the ground and the control system has carried out a first tether over-run process t» attempt to separate the payioad eonpling apparatus f m the payioad, the control .system may determine whether the payioad coupling apparatus has actuall separated from ih payioad, hased on the current of ihe motor (e.g by performin Mocks 2ό¾2 and 2604 of method 2600). Fo example, after operating the motor to cause tether over-ran, the control system, may operate the motor to begin retracting the tether, and If tire payioad is still attached to ie payioad eoupiiug apparatus, die extra weight of ihe payioad may eanse the motor to draw more current. Accordingly, the control system may determine that the payioad is still attached to the payioad coupling apparatus by detecting thai the ttib!or current is threshold high.

\Q$79$ Responsive to making such a deiermhiatioa, the control system may repeat the processes of lowering the payioad to the ground, operating the motor to cause over-run of the teffter (this ii e, perhaps, fey some predetemiined additional length), and then ptdiing upwards on ihe tether to tes for payioad, separation, shown in bioefcs 3402 and 3404. These processes rna be repeated a number of times until the control system determines that d e ^• pay load has separated from the. payload coupling apparatus or until a threshold number of repetitions has occurred, as showa by block 3404.

j{S38f I The ccffitrol system: m y track how many times the processes of causing overran of the tether and testing for payload separation lave he carried out and n y deteHniBe that these processes teve been repeated a threshold Bnmber of times without successfully releasing the payload from, the payload co-mling apparatus, as shown by block 3406, Responsive to making this determination, the control system may decide to abandon further a tempts to separate the payload from the payload coupling apparatus and may instead decide ¾ separate the tether front the- UA ^' V by operating the motor et allow the tether to unwind dhritig ascent of the UAV, as shown . by block 3408,

i38I| hi practice, the control system B y operate the motor to allow the tether to uawiBd by cafciroilmg a Baximnm current supplied to the motor. By limiting the maxhmiBi current supplied to the motor, the control system limits tb© amount of feree that the motor can exert OR tether. More specifically, the control ^' system -amy limit: the ffiaximiiJft currcpt to a small -enough, vatee t!iat the motor's maximum upward force exerted op the tether is smaller in magnitude thas the downward force on ;lie tether ue to gravitational forces op the payload. As a result, the UAV may Hy upward, arid the tether: will. eoBiitt»e to unwind due to the downward: force on the tether exeeedipg the -upward, forte- rom the motor. In othe examples, the control system may merely turn off the moto , allowing it to spin freely, ta order to obtain: simil ar results .

| 382| Further, as noted, above,, the tether a fee disposed on a spool. More specifically , a first end of the tether ma be uon-fixedly wound, oft the spool . As such, when the tether completely unwinds from tlie spool, the tether may detach and fall away from: the spool. Thus, while the- control system operates the motor to allow the tether to unwind, the- control system m y further cause the UAV" to initiate a flight to a different location (e.g,, a return location ^' ) soch that the flight of ate UA¥ unwinds- the tether and separates the tether from the spool, thereby releasing th tether from the UAV, as shown fey block 3410.. In this manner, when the payload coupling apparatus is unable to detach f om the payload, both the ^• payload- and the tether may be left behind, at the delivery location, allowing the I AV to safely navigate away.

Snag Detection

|0383| A IJAV carrying out tethered picku and delivery of pay loads accordin t the processes disclosed herei may f¾d itself operating in various diicxeat types of environments with various different issues to address.: One issue may Invoke undesirable or unexpected forces exerted OH the tether. For instance, a person t y excessively yank on the tether, or the tether might get soagpd on a moving or stationary object, resulting in a downward force on the tether. Other examples are possible as well. M these s tattions, if the downward force is great enough, the UAV could, h puiled out of its flight, perhaps damaging the UAV, the payload, or nearby persons or property. Accordingly, the control system may defect &ea certain forces are allied to the tether dining delivery o a payload and responsiv ly t ke mmedia! action by aijo hig the tether to ^■■ unwind front its spool

|038 J Figure 3 is a. flow chart illustrating metnod 350 of detectin and addressing undesirable downward force on a tether when lowering a payload toward the rowd, Method 35 0: ma be carried out by a UAV such as those described elsewhere herein.. For example, method 35C.H) May be -earned out by a control system of UAV with, a winch system, Further, the which system rnay inctede a tether disposed n a spool, a motor operable- in a first mode and a. second mode that respectively counter an assist ^' un ind ng of the tether dye to gravity (e>g. _i: by driving the spool foward or in reverse), .a payload eooplsng apparatus tbat meehanieaily eonpies the tether to .payload, and a payload latch switehable between a closed position that prevenis the payload from being lowered f drts the UAV aad aa open position that allows the payload to be lowered ironi the UAV,

f 03$5| As shown by block 3502, met o 3500 iftyotves the control system of the UAV operating the -motor to cany ont tethered deliver of a payload (e,g,, b petforming nrethod 1800). Dari the process: of delivering the pay load to a target location,, the control systeat may detect an imdesirahle downward f rce on the tether. As described above, th preserjce o f add itional weight (or in ibis case, the presenee of a sufficient downward force) on the tether may result in an increase in. current supplied to the motor in order to maintain desired rotational speed of he motor. As such, the control sy stem may detect an ruxfesira e ■di w.«waKi force on the tether based on the motor current.. Further, in order to avoid false positives, the control system titay also consider how long the motor current is increased, f0386| .Additionally, the con trol system may -consider aa nnwoaad length of the tether when detectin an undesirable downward force. For instance, in order to limit the detectio of down ward forces to sources at or neat ground le vel (e.g. _< detecting a person yanking on the tether), the control system may also detemiine how far the tether has been unwound from the spool in order to determine whether an part DF the tether is at or neiir ground level. Othe exarnptes are possible as welt

|Q387] T tJS in practice, dtain the process of delivering the payloa to a target location and while the If AY is in flight, the control system may determine an unwound, length of ik s tethef based on encoder data representing a rotation of the tether spool, and die control .s stem may $¾m»iae a motor earreal based oa a eirrenl sensor of the motor the power systeni of the 0AV\ Firmer, the . control system ftsay. determine mat both ^' (a) the a» ®jad l a di f tethe is greater than a threshold length and b) the motor current of the motor is greater than .. a threshold enrreat, for at least a predetermined timeotit: period, as shown by block 3504. Responsive to making such a -determination, me control system may operate .the motor t© allow the tether to unwind hen me 11 AV ascends (e ₍ g., as described above lta respect to block 340 ? of method 3 00},, as shown by block 350b. And further responsive to makin the detern inatipri, the control system may eapse the II AV to initiate a flight to a difteteni location. { ^' e,g:.„. a retina loeaboa), och thai the Sight of me tlAV anwinds the tether sad separates the tether from ibe spool, thereby releasing the tether from the IJAV,. as shown by block 3508. this manner, when an undesirable downward force is exerted on the tether, the tether may unwind and detach from the U AY, allowing the IJAV to safely navigate away, |0388| In other examples, rather than detecting a snag aid responsively operatin the motor to unwind nd release the tether, snags may be resolved by imposing a current limit ø« die motor when ptckiag u a payload. Omitlng the motor current to a naashnam value hmiis die amount of force the -motor, can exert on the tether, which may prevent a UAV f om.: crashing if the tet er becomes snagged,. For iastance, if the- cu ent limit is low en ugh that the rn xi inm tipward force exerted o the t ller by the motor is weaher tha a downward: forc on the tether, men the current limit on the motor may allow the tether to compleieiy ■unwind and detach om its spoof should the EJAV fly away while the tether is snagged,

[0389 * addi tion to experiencing undesirable forces during deli very o f a pay load the tether may also -experience- undesirable fo ces during pieknp of the payload. For instance, when winching a payload from the r und teward me UAV, me payfoad and/or the tetter .may become snagged on various objects, suds as trees, buddings, or various other nearby oh jee is. As another- example,; m tsnexpectediy heavy payload. eotdd be attached to the tether, resulting in as excessive downward force on the tether that prevents the tJA.V iro i lifting the payload, Aeeordisg!y, the eonlfo! system, may detect when certain forces a¾ applied to the tether during peknp of a payload aad responsively take remedial action.

[039 figure 36 ts a flo chart ilins crating a method 3 0 ^; of detectin and addressing undesirable downward forces oa a tether when winching a payload toward a JAV, Method 3600 may he carried out by a O V saeh as those described elsewhere herein. For example;, method 300 may he carried ota by a control system of a IJAV with a which system. Further, the winch system may include a tethe disposed on a spool, a motor operable in a first mode and. a second mode that respectivel counter a&d assist unwinding of the tether due to gravit (e,g., bf driving fee spool ferward o is reverse), a payload Coupling appiirat s that mechanically eoitpies fee -tether to a payload, sad a payload latch switchsble between a closed gesitiotJ that prevents fee psyioad from being lowered tforn the UAV and an open position that allows the payload to be lowered from fee UAV.

J039IJ As -shown, by block ^" 3602, method 3600 involves the control system of fee UAV operating the motor to carry oat tethered: delivery of the payload (cg^ by pertorming method. 1700). During a process of --picking o fee payload to he delivered, and while fhe UAV is over or nea to a piekap location, he control system may deternhne that a psyioad coupling apparatus is mechanically coispled to a payload (e.§., based on fee rootor ciittcfit as described above wife respect to method 1706) mi may responsively operate the motor i retract the letter and Hit fee p lo d toward fee UAV, as shown by block 36¾4,

[3392] While retracting the tether, fee control -system may detect an error condition when, fee tether sod/or the payloa becomes snagged. In order to detect a. snag, tlie control system, m y monito the mot r current. As described a ove, adding a do wnward force to the tetter may cause an increase in motor corrent in order to counteract the downward !oree and; maintain a motor speed set by a speed controller, Th»s, when the tether and/or tire payload becomes snagged, the motor current may nstead as the motor attempts to maintain the rotational speed set b the speed controller. However, as also noted above wife respect to method 1.700, as increase: in motor CB te t: taa be indicative of the payload reaching fee UAV after winching is complete . Accordingiy, fee control system may also niorntor and consider an unwound length of the tether when detecting a snag. For instance,, if the turwonnd length of the tether indicates that the payload has not yet reached the UAV, then the control system may detect a snag. On the other hand, if the -unwound length of the tether indicates that tlie payload ^' has- readied tlie UAV, linen the control system may not detect a snag, Thus, while retracting fee tether with, fee payloa coupled meret©, the control system may detect an erro coadirion whe boih (a) an niiwound length of the tether is greater than threshold ierigth and (b) motor current of fee motor is greater than a threshold current, as shown by block 3i¾b,

{&393$ la any ease, af¼r detecting the error condition _s the control system may make an attempt to correct tte: error condition by operating the motor to: unwfed fee tether (e.g, by a predetermined length), and may then resume retracting the tetter, as shown hy block 3608, Unwinding the tether ay add slack to the tether, perhaps allowing the weight of the payload to undo the detected snag. In some examples, the control system, may cause the UAV to repos tieu itself befbre iestttaiag tetraetiag the tether m order to. improve the ehattces of undoiug the snag asd reduce the chances of encountering the mt saag.

{0394} . if, after resuming the refracting of the tether, the control system detects that the error condition is still present Ce,g., as sfown b Mock 3606), the control system may repeat the attempt to correct the error condition by repeating block 3SQS, and the control system, may monitor the number of repeated Doweetion attempts. Once the control system detennmes that a predetermined .number of attempts to correct tne error condition bave been made without successfully correcting the error condition, the control system ma responsively end ilie process of picking up fce pay load and initiate a pay load delivery process to rer n) the payload to the gr un at or near the pickup !ocaiioa,. as sbo ii b block 3610. More specifically; the control system m& operate the moto to lower the payload to the ground as if .it was perfomiing a payload delivery according to method 1800.

€. Failure to I¾k Up Payload

|0395| QceasTORaiiyj ¾¾eR a iJA.V attempts to p ck up a payload for teihered deliver (e.g., by perlbrming method i? l}) _:s the 1JA.V ma retract (tie tether ½fore a payload has been attached t the tether. For instance, while performing trtetliod 1.70 _s: m control system of the UAV may falsely etCMiine that a payload is attached to the tether at bloclis 1708 sad j 10 (e. _. g;,, -due to someone or sometbitig pwlling on the tether during the prodetermraed attachment yeritlcaiion period) ami respoasivel Qpe ie the motor to retract the tether. Accordingly, fee control system ay be eoai tred. to determine,, during retracting of the .tether, that a. payload is not actually attached to she tether

f 0396| i re: 37 is a flow chart of a method 3700 of detecting that the UAV tailed to pick np a payload. Method. ^' 3700 may be carrie out by a UAV such as those described elsewhere herein. For example, method 3700 may be carried out by a control system of a UAV with a which system. Further, the which s stem ma include a tether disposed on a spool, mote operable ¼ a first mode arid a second mode that respectively coupler and assisi unwinding of the tether due to gravity (e.g., by driving the spool forward or in. reverse), a payload coupling apparatus that mechanically couples tire tether to a payload, and a payload laich swttchable betwee a closed position that prevents the payload fmm bein lowered fi tB the UAV and an. opea position that allows the payload to be lowered from the UAV,. j¾¾>7jj ^' As shown b block 3702, method 370f> involves the control, system of the

UAV operating the motor to carry out tethered deliver of the payload (e.g., b performing meihpd Τ7Θ9 . During a process of picking up the payloait to be delivered, and while tbe UAV is over or near to a pickup location, the control system may operate the motor to unwind the teiher and tower a payioad eou &ag apparatus to m, expected payioad attachment attitude, as shown by block 3704. As toted above, fee paylead aitaehnienl aitir e may e an slttojde at which a human, or perhaps a robotic device, may grab the payioad coupling apparatus for attaeinng the coupling apparatus to a payioad. f or instance, the payioad attachment al ti tu de may be an altitude less than two meters above ground level

|039Sf .Alter lowering the tether, fee control syste - may wait for a predetermined pay oad aiiachmetit period, as shown by block 3706. Thi ariaclimeat period allo ws time for 3 human, or perhap a robotic device, to attach a payioad to the payioad coupling apparatus. :039¾ h the payioad attachment period ends, fee eoatrol system ma perform an attachment verification process _* as further shown by block 3¾i>. in particular, the attachment verification process may involve the control system opetatiu fee motor so as to counter unwinding of the tether for a predetemiined attaehaient verification period (e.g., by pulling upwards on the tether in order to bold fee tefeer in place of retracting fee tefeer at a certain rate),, as showsi by bioek 3?(¾a> The n»tor ^■ current required to bold the tether in place or retract fee tefeer at a certain rare will be greater when the payioad i attached, due to the added eight of fee payioad As such, the attachment verification process may ferfeer involve the control system deiennMag, based at least in jsart on motor entreat during t¼e predetermine attachment verification period, whether or not fee payioad coupling apparatus is mechanically coupled to the payioad, as shown by block 3706b. For instance, as discussed above, die control systeni may determine the motor current based on data from a entreat sensor of the motor or of fee power system of the UAV. If, doting the attachment verification process, fee motor current exceeds a threshold entreat value, then th control system may determine feat the payioad is eonpled. to the payioad coupling apparatus. On the other hand, if the otor current is below the tteshoid current value, then the control system m y deie.tinl.tie that fee payioad coupling apparatus Is not eoupled to die payioad,

(¾4O0J Further, when the control system, determines that fee payioad coupling apparatus is not -mechanically coupled to fee p yioad, the control system can cause the UAV to repeat, the lowering of the payioad coupling apparatus and fee attachment verifieatio process in order to reatiern f pickup of fee payioad, and i some embodiments these processes may only be repeated up to a ptedetemfeied number of times, as shown by Hock 3706, At this point, rather than attempting to piek u fee. payioad again, the control system may catsse the UAV to abaudoa the picfenp anil navigate away. In prae see, for instance, fee control system may determine feat the attachment verifieation process has been repeated predetermined number of times without success l coupling of the payioad couplin appata as to the payioad, aad responsively i date a. process to cancel pickup of the payioad and initiate tight o-f the UAV to a next, difeea location, as shows by block 798. The dtf%rent location may be anothe cfcofj location, or it may be some other location, such as a UAV dock for docking &Qt storing the UAV. Other examples are possible as well...

}0:461| As noted above, there may bo situations wbe control system, falsely determines .that a payioad is attached during the payioad verification period,, and the control system ma responsively cause ^' the motor to enter a winching state to retract the tether toward the U AV. Accordingly, in order to .reduce such false determinations, the duration of the ^• pre ermitted attachnient verification period described ahove may be increased. Additionally or alternatively, the control system .may be further configured to perform the aitachmeBt verification process and tether lowering: process as shown by block 3706 while operating in the winching state.

B, ayioad Lisle!* Failure

|Θ48>2} As described above with respect to method 18CM1, whe AV successfelly picks up a payload and pulls the payioad or a f a load coupling apparatus hno a receptacle of the UAV, the control system may close a payioad latch to secuie the payioad to the U V. However, there nifty e situation where the control systets fails to close the latch (e.g., due to -a t o structioa or some other -issue) or where the control system closes the ^' latc but the closed latch fails to secure the payioad to the UAV. Accordingly, the control system may be. configured to determine whether the payioad latch has successfully secured the payioad to the

UA.V

(0403} IB some embodiments, the control system may operate the rooter to pull upwards on the tether prior t atteBipting to close the payioad latch, if the payioad and or payioad coupling apparatus have reached the UAV receptacle, the payioad coupling apparatus Is pressed u against {he UAV sueb thai dse motor cannot retract the tether any turther. At this point closing fee payioad latch ma successfully -secure the payioad and/or the payioad coupling app ratus to the IIAV. On the other hand, if the payioad. and/or payioad coupling: apparatus vc. not yet reached the UAV receptacle, then the motor may still h retracting the tether, and closing the payioad eh at this point would unsuccessfully secure the payioad. Accordingly, when closing the payioad latch and or fo time- dumtton; afte closing the payioad latch, the coBtroi system may be configured to monitor the motor speed, to determine whether the payioad latch, successfully closed and secured the payioad to the UAV, For instance,. esponsive to detecting that the motor speed is above a threshold speed,. the .control system may deterroise thai: the payioad latch failed to successfully close and½f secure the payioad to the liA V.

j0484f lh other eo odmMts, after attempting to close the payioa latch, th control system may detect pay load latc failure by operating the motor to eawaid the tether predetermined lengifi. If the payioad latch was successfully closed to engage the payioa or payioad: couplmg apparatus, iheo tire payioad or pay load coupling apparatus may h arranged within tie UA V receptacle such that, ail or a portion of the eight of the payioad rests on the j load !i tefe rather than the tether, asd the motor current might he below a threshold current (e.g., roximatel zero). On the other hand, if the payioad latch felled to close, the¾ the weight of the psyl ad might be sis potted by the. tether, and the motor current required to s«pport the weight of the payioad might be above a threshold current. Accordingly, the coatxoi s stem may detenrjirre whether the payioad. latch successfully closed based on the

fO 08 Oace fttc UAV re ches a. source location for pickup of a pay toad, the control system may receive a cotHrnsnd to pick up the payload and may responsiveiy enter a payload ^• g ekup, rood© (e.g., b performing method 1?ΐ >), As shown b state diagram 3¾00, the payioad pic;k«p mod may hrelude a LG ER G HOOK, state 3804, during which the control system operates the motor to tia iiid the tether i¾m a spool asd lower a payload couplin apparatus toward the ground.. While state 3804 refers to the payload coupling apparatus as a hook, the payioad coupling apparatus can. take various fobas, as discussed above. The payload coupling apparatus ma be lowered t a predetermined payioad attachment altitude based on he altitude of t e UAV ^' . Gsee the pay load coupling apparatus reaches the payioad. attachment attl&de■(? ., when the. control system determines- that me length of the unwound tether is at least a threshold length), me control systeiB may cause the L ^' AV to enter a WAITING FOR PAYLOAD state 3806 for a time delay, during which the con rol system operates the motor to hold the payioad coupling a paratus at a, substantially constant altitude, thereby allowin the payioad to be attached to the payload coupling apparatus. Additionally, i the eoniro! system fads to determine that the payload coupling a paratus has beers lowered to the predetermined: payload aitaelunent altitude within a set iirae period fe.g., a timeout period), the control system t y respottsivel advance, to tfee WAXHNG FOR PAYLOA0 state 3806.

flW8S¾ From the WAITING FOE PAYLOAD' state 380 once the time delay elapses, the control systern enters a VERIFY PAYLOAI) state 3 8. During; this state, the control system deter. mines whether the payioa is attached to tire pa load coupling apparatus based on a motor current: supplied to the motor whe the motor attempts to hold the payioad coupling apparatus at a constant altitude or begins to retract the tether toward the LIAV, If the motor current. is below a threshold current during the E IFY PAYLOA state 3808, the control system returns to the LOWERING .HOOK state 3804 to reattempt atiaehineot of the payload. As described above with! respect to niethod 3700, this repetition may be repeated a number of times until limit is reached, Qnce the limit is reached, the control system: may cause the UAV to retract the tether, ascend, a¾d perhaps return t the IDLE state 3802 froi whic tfee OAY may navigate to some other location,

{0418J On the other hand, if, during tfe. VERIFY ^' PAYLOAD state 380.8, the control system determines that the pay load, has been attached to the payload coupling apparatus (e.g., by deierrohiirjg after a time delay that the motor current is t least a threshold current), the control system, may este a WfNCHfNG PAYLOAD state 3810, During this state, the. control system may operate the motor to retract the tether and pull the payioad toward the UAV. As escribed above with respect to method 3700, &e control system inay also mcyaiior motor cttrrei in ills state t¾ determine -whether a false positive was obtained during the VERIFY PAYLOAD: state 3808 (e ., by detectin tbsi the motor c«rreof is ihreshoid low). Additionally, as noted above with respect to method 3600, the control system ma monito the motor cnrrenr during die WINCHING PAYLOAD stale 3810 hi order to detect whe the tether becomes snagged: (e.g., by detecting; that- th motor curreut is threshold high). Responsive to detectin a snag _s the control system may operate die motor to lower ie payload a predetermined length and rearterspt winching the payload _* After a threshold ^• ft ftiiter of a tem ts to remove die snag, the coahoi systeni may operate ie motor to lower the payload to the: ground, and ^■■■ abandon pickup of the payload. This may involve ^advancing to a DES ENDrNG state 3822, which is discussed in more detail below.

10 111 While operatin in th WINCHING PAYLOAD state 3B10, if no snags are: detected, or if alt detected snags are resolved, the control system ma detect, that the payload is within a threshold distance of die PAY by measurrng; a number of rotations of the tether spool) and responsively enter an. ENGAGING- FAYLOAD state 3812. Daring this state, the control system may increase the current supplied to the motor for a predetermined. hrse period iu order to alismiit to pull the payload into, and orient ike payload within, receptacle of the LAV, ¾ during this state,, the control system detects that the motor current is below a thresnold eurrera artd or that the tetier is unwound at least a threshold length, then the control system may responsively determine that die payload is too far from the UAV and may re-aster the lNCHJHG F LO D state 3810 - until the control system again detects: thai the payload is close enough to the UAV to advance to the ENGAGING PAYLOAD state 3812:.

(04121 On the other hand, if, during the ENG GING PAYLOAD state 3812, the motor caucus remains ihreshoid high and the unwound length of the tether indicates that: the payload has reached the LAY, then the -control system enters the LATCHING PAYLOAD state 381 During mis state, the control system switches the payload latch to the closed position, thereby preventing the tether an&Vdr the payload from, descending from tlie UAV. As described above, the control system may determine whether the pa ioad latch was successftttly ciosed by monitoring the motor speed aad or by operating the motor to attempt to lower the payload and monitoring the motor current, if the control system determines that the payload latch was not : successfully eiesed, the control system may return to the WiNCHiNG PAYLOA state 3810 and reaitempt to lift and engage the pay load. But if the control: s stem determines that the pay load latch was successfully closed, then the control system may enter- a WAITING TO DELIVER state 3816.

_. {04-13! The WAI ING TO DELIVER state MM may be sfehiar to the IDLE state

3802 where the payload is secured to the LI V, and the control system operates die mater to- kee die payload stationary. If, after a time delay^ the control system detects that die motor speed s greater than a threshold speed, f s may indicate that the payload is sot sufficiently secured to the ilAV, and the -control system ma responsiveiy return to the WlNCHiNG f AiYEOAD state 381». Odiervise. entering: the WAITING TO DELI VER, state 3816 .signals the end of the piekiip mode,

{ 414{ While to the WAITING ΓΟ DELIVER state 3816, the control system may receive a command to deli ver the psyioad. a id may resporjsi vely enter a delivery mode (e.g., by performmg Method 1800), The delivery mode may include a PRE-DROP TENSION state 3818. In this state, while the payloa latch .is closed, the control, system may operate -the motor to Kit the payload (e.g. _* by setting the desired tether speed to 1 m s or some other s eed i -an upward direction, or by setting the motor current to a. ^determi ed- valiie) _* thereb femcfv-tttg- the weight of the payload If ta the payload latch and making it easier to open the payload: latch.. While in the PRE-DROP TENSION state the control system may open the payload latc and advance to the POST-DROP TENSION state 3820 alter a time delay. Its. this state, the control system may operate the. motor to hold the teiher in a constant position for a; predetermined, amoitat Of time to allow the weight of the payload to pull the payload firmly against the payload co pling apparatus, thereby reducing any chanc that, the payload might slip off and detach from the payload coupling apparatus. After th predetermined amount of time has passed, the control system may enter the DESCENDING tate 3822.

[04151 & hoth the PRE-DROP TENSION state 3818 and the POST-DROP

TENSION state 3 H 20, If the control s stem eteeis that .the payload lia traveled at least a threshold distance (e.g., by measuring rotatioa of the spool),, then this may indicate mat an error lias occurred (e.g., premature detachment of the payload from the payload coupling apparatus or na ping of the tether) because the spool should remain substimtiaiiy motionless duritig these states. As a result t delecting sae an ertoiythe control system may return to the IDLE state 3802 and cause, the 0 A¥ to navigate to a location where it. ma he serviced. }04l6f in the DESCENDING state 38:22, the- control system may operate the motor to unwind the tether according, t a predetermined descent profile that .specifies: a constant or varying operational speed of the motor Upon detectirs that the tether has no wound at least a predetermined amount fe.g, _s detecting that the payioa.d. is within -a threshold distance of the j auBui based on m altitude of the tJA-V), the: control system may eater a WAITING FOR TOUCHDOWN state 3824. & mme exaaip!es, the control system may also b confi ured to advance fern the DESCENDING state 3822 to the WA1TW6 FOR TOUCHDOWN stat 3824 if a thresho amount of time elapses in the DESCENDING state 3822 without advancing te the WAITING FOR TOUCHDOWN state 3824,

{0 171 ^' m fit© WAITING FOR TOUCHDOWN state 3824, the control system rosy monitor tie motor currerit and its operatioriaS speed in. order to detect whether the payload has reached the ground. Specifically, upon determining that both the motor current and the motor speed are thresliold lew, the control system may enter a POSSIBLE TOUCHDOW stat 3826 to verify that the payload has in facitfeac ed the groand. The eoBttol system ma fee. configured to remain in lite POSSIBLE TOtJCMDOWN stat 3826 for a predetermi ed amount of time. If, during tibat time, either t½ motor current or the motor speed hecomes threshold, high, this ma Indicate that rhe payioad has not yet reached, the ground, arid tiie control system ay retitrn to the WAITING FO TOUCHDOWN state 3824. However, if, during the duratioii of the POSSIBLE TOUCHDOWN state 3826, the motor current and the motor speed remain threshold few, ibis may ittdicate that tile payload has in tact reached the groisud, and the control system may responsrvely adv nce to ^' a TOUCHED DOWN state 3828. in som csarpples, the control system ay also fee configured to advance from the WAITING FO TOUCHDOWN state 3824 to the TOUCHED DOWN state 3828 if a threshold amount of time elapses m the WAt iNG FOR TOUCHDOWN state 3824 without advancing t the POSSIBLE TOUCHDOWN state 3826.

ί04!8 Once in die TOUCHED DOWN state 382:8, the control system may operate the motor to cause over-aiR of the tether such that the pay load eoitpihig apparates continues to lower while the payload retnas stationary o» the grc¾»d, Costiffuirig to lower the pay load coupling apparatus may eause the pay load cott Utig apparatus to detach, from die payload. After causing tether over-run for a predetermined atnooni of time, the control system may enter VERITY RELEASE state 3830 in. order to determine whether the payload ^■ coupling apparatus did in fact separate from the paylbad.

fi)419| In the VERIFY RELEASE state 3830, the control system: ma operate the motor to pull upwards an the tether. Based on the motor current when pulling upward on the tether,, the control system may determine whether or not the payload has been released from the payload couplin apparatus. If the motor currerit is threshold high, this may nidieaic: that the payload is still attached, and the control system may , return t the TOUCHED DOWN ^' state 3828. This process may be repeated op to a predeiemiiaed -number ø£ limes, at which point the control system rnay enter a FREE SPIN state 3832.

|042i| in the FREE SPIN state 3832, the control, system ti y operate the motor to allow the tether to coBipietely (sti I such that the tether iMseersaecis and falls away fat the IJAV. This ma he achieved by litaiting t e .motor etu ent to a sufficiently tow alue that the motor is unable to counteract ike downward force on the tetter caused by the gravitational pull &xt the payload., Alternatively, tie mot r can .be ska off completely (e.g. , limitin the motor current to 0 A),

J042I1 Referring back to tte VERIFY RELEASE state 3839, If, throughout a p:Fedei«rrttine<! dnration, the motor enfrent reasams thteshoid low, this ma indie-ate that the. paytoad has ia fact separated from the payload coupling apparatus. aBd die control system may respoBsively advance o an ASCENDING state 3834.

J 42 J ¾ the ASCENDING state 3834, the c n ol system may -operate the. motor to retract the tether and the payioatt cospliag: apparatus up toward the IJ AV accordi g to a predeterB¾ned ascent profile that specifies constant- or varying operational speed, of the motor., Once the eo-nttol system detetnnae that an ort euad. length of the tether Is below a threshold length such that, the payload coupliag apparatus is sirffieientiy close t the tlAV (e.g _> based on a. measure number of rotations of th e spool) , the co n rol system ma eater an ASCENDING PAUSE state

}0423f hi the ASCENDING PAUSE state 3836, the control system; may operate the motor i& halt the refraction of the tether. Once ^tracti n of the tether is halted, the control system may control a movemeat of the OAV is crde* to- dampen any _. -escilMons -of the teihsr that may have occurred dating- the ASCENDING state 3834. .After damping the tether oscillations, the control system may-eater a FINAL ASCENT state 3836,

f&424 la the FINAL ASCENT state 3836, t e control system ma operate die motor to resame retf acting the tether. However, i« tills state, the tether ma be retracted at a slower rate than that of the ASCENDING state 3834. This slower rate may introduce weaker oscillations on the tether. Also dnring the > FINAL ASCENT state 3836, the control system.: inay monitor the .motor current to determine when the payload eottpliag apparatus reaches the II AV. In practice, when the pay load coupling; apparatus reaches th e UA V , the apparatus is pressed against the IJAV, the motor speed drops to zero, .and the motor current increases in an attempt to increase motor speed. Accordingly, the control system may determine that the payload coupling apparatus has reached: the HAY based on the motor current exceeding a threshold current, Responsively,. die control system may enter, an E GAGING state 3840,

L AV motor when retracting {he tether, as sh wn by states 3834 to 3840, when compared to lowering the tether, as sh wn by states 3 $ 18 to 3828. This is because the tether is more likely to encounte a sna when retracting the tether. Imposing lower current limit reduces the amount of force that the motor ma exert on ine tether. This ma prevent the motor fro causing the UAV to crash by eoniiotimg to winch the UAV toward a snag. And as noted- above, if the current limit is low enough that tire ax mum force of the motor is Weaker fhan a dow' atd force on the tether, then the -current limit on the motor may allow die teiher to completely unwind and detac from its spoof, should the UAV fly away while the tether is snagged. Similar methods may ¾e eniployed when initially picking itp a payload during states 3806 to 3814.

XIV, AtWiti ssaS Aspects

(04281 In some embodiments, the coatcol system of the UAV may he configured to calibrate th ro ar encoder a«d speed controller of the motor upon startup of the system, fti practice, when the UAV system is initially powered on, the motor should tse stationary. Accordingly, the encoder data should also indicate that tie motor is stationary. If the encoder data indicates, otherwise;, thee an offset may be applied to the encoder data to account fer My inconsistencies.

[0429J l re control system may further test the f iction of the motor on startup of the

D.AV system. Based on the measured motor friction, an offset may be applied to various motor cmrent settings to account for the measured motor friction. Over time, the friction of a DC motor may vary. Therefore, measuring friction on every startup and adjusting motor current settings accordingl may enable consistent operation over ine life of the motor

w e varety o rent con guratons, a o w ic are conternpate eren.