Title:
NULL SPACE CONTROL FOR END EFFECTOR JOINTS OF A ROBOTIC INSTRUMENT
Document Type and Number:
WIPO Patent Application WO/2022/074526
Kind Code:
A1
Abstract:
The disclosed embodiments relate to systems and methods for a surgical tool or a surgical robotic system. One example method includes providing a redundant degree of freedom (DoF) for an end effector joint of one DoF by driving the joint with two actuators, calculating a position displacement of the joint to effect a desired end effector movement in response to an input command, calculating a first movement of the two actuators based on the position displacement of the joint and a second movement of the two actuators based on a second control objective in a null space corresponding to the redundant DoF, and driving the joint according to the first movement and the second movement to effect the desired end effector movement while accomplishing the second control objective in the null space.
Inventors:
ZHANG XIAOBIN (US)
CHATZIGEORGIOU DIMITRI (US)
CHATZIGEORGIOU DIMITRI (US)
Application Number:
PCT/IB2021/059042
Publication Date:
April 14, 2022
Filing Date:
October 01, 2021
Export Citation:
Assignee:
VERB SURGICAL INC (US)
International Classes:
A61B34/00; A61B17/29; A61B34/30; A61B90/00; B25J9/16
Domestic Patent References:
WO2016152046A1 | 2016-09-29 | |||
WO2014146113A1 | 2014-09-18 |
Foreign References:
KR20140113209A | 2014-09-24 | |||
US20140081461A1 | 2014-03-20 | |||
US20120158017A1 | 2012-06-21 |
Other References:
PETROVIC PETAR, LUKIC NIKOLA, DANILOV IVAN: "Compliant behaviour of redundant robot arm - experiments with null-space", SERBIAN JOURNAL OF ELECTRICAL ENGINEERING, vol. 12, no. 1, 1 February 2015 (2015-02-01), YU , pages 81 - 98, XP055919485, ISSN: 1451-4869, DOI: 10.2298/SJEE1501081P
Attorney, Agent or Firm:
SHIRTZ, Joseph F. et al. (US)
Download PDF:
Claims:
What is claimed is: 1. A robotic method comprising: providing a redundant degree of freedom (DoF) for an end effector joint of one DoF by driving the joint with two actuators; calculating a position displacement of the joint to effect a desired end effector movement in response to an input command; calculating a first movement of the two actuators based on the position displacement of the joint and a second movement of the two actuators based on a second control objective in a null space corresponding to the redundant DoF; and driving the joint according to the first movement and the second movement to effect the desired end effector movement while accomplishing the second control objective in the null space. 2. The robotic method of claim 1, wherein the joint is an articulation wrist coupled to two actuators through cables. 3. The robotic method of claim 2, wherein the second control objective is maintaining a minimum tension on the cables. 4. The robotic method of claim 3, wherein the minimum tension is maintained by a control system having an error signal based on a first torque of one of the two actuators and a second torque of the other of the two actuators. 5. The robotic method of claim 4, further comprising: calculating the error signal (e) according to: e = max ( τ min + τ1 , τ min - τ 2), wherein τ min is the minimum tension, τ1 is the first torque, and τ 2 is the second torque. 6. The robotic method of claim 2, wherein the null space corresponding to the redundant DoF for the articulation wrist is described as a vector [‐1, 1] or [‐1, 1]T. 7. The robotic method of claim 6, wherein the null space corresponding to the redundant DoF for the articulation wrist provides a relationship between the first movement of the two actuators and the second movement of the two actuators. 8. The robotic method of claim 6, wherein a relationship between the first movement of the two actuators and the second movement of the two actuators includes where k is a constant number. 9. The robotic method of claim 2, wherein a physical displacement of the joint (θj) is provided by: based on a first position (θm1) for a first actuator and a second actuator position (θm2) for a second actuator, and at least one property constant includes first constant a and second constant b. 10. The robotic method of claim 1, wherein the joint a closure jaw joint of the end effector. 11. The robotic method of claim 10, wherein the second control objective is providing a certain torque at the closure jaw joint. 12. The robotic method of claim 11, wherein the certain torque is maintained by a control system having an error signal based on a first torque of one of the two actuators and a second torque of the other of the two actuators. 13. The robotic method of claim 12, further comprising: calculating the error signal (e) according to: e = ‐ τ1 + τ 2, wherein τ1 is the first torque, and τ 2 is the second torque. 14. The robotic method of claim 10, wherein a physical displacement of the joint (θj) is provided by: based on a first position (θm1) for a first actuator and a second actuator position (θm2) for a second actuator, and ai is a constant coefficient from a tool calibration process. 15. The robotic method of claim 10, wherein the null space corresponding to the redundant DoF for the closure jaw joint is described as a vector [1, ‐1] or [1, ‐1]T. 16. The robotic method of claim 15, wherein the null space corresponding to the redundant DoF for the closure jaw joint provides a relationship between the first movement of the two actuators and the second movement of the two actuators. 17. The robotic method of claim 16, wherein the relationship between the first movement of the two actuators and the second movement of the two actuators includes where k is a constant number. 18. The robotic method of claim 1, further comprising: determining a projection of a control signal for the position displacement of the joint to a vector for the null space, wherein the projection represents the second control objective. 19. An apparatus to provide a control objective using a null space of a redundant degree of freedom of a surgical tool, the apparatus comprising: a tool driver including a plurality of actuators providing a redundant degree of freedom (DoF) for an end effector joint of one DoF; and one or more processors configured to: provide a redundant degree of freedom (DoF) for an end effector joint of one DoF by driving the joint with two actuators; calculate a position displacement of the joint to effect a desired end effector movement in response to an input command; calculate a first movement of the two actuators based on the position displacement of the joint and a second movement of the two actuators based on a second control objective in a null space corresponding to the redundant DoF; and generate a joint command for the joint according to the first movement and the second movement to effect the desired end effector movement while accomplishing the second control objective in the null space. 20. A non‐transitory computer readable medium including instructions to cause one or more processors to perform: identifying a redundant degree of freedom (DoF) for an end effector joint of one DoF by driving the joint with a plurality of actuators; calculating a position displacement of the joint to effect a desired end effector movement in response to an input command; calculating a first movement of the plurality of actuators based on the position displacement of the joint and a second movement of the plurality of actuators based on a second control objective in a null space corresponding to the redundant DoF; and driving the joint according to the first movement and the second movement to effect the desired end effector movement while accomplishing the second control objective in the null space. |
Description:
NULL SPACE CONTROL FOR END EFFECTOR JOINTS OF A ROB
OTIC INSTRUMENT FIELD [0001] This disclosure relates to control of a surgical rob
otic tool with one or more actuators. BACKGROUND [0002] Surgical robotic systems give an operator or user, s
uch as an operating surgeon, the ability to perform one or more actions
of a surgical procedure. In the surgical robotic system, a surgical tool or instrumen
t, such as an endoscope, clamps, cutting tools, spreaders, needles, energy emitters, et
c., is mechanically coupled to a robot joint, so that movement or actuation of the r
obot joint directly causes a rotation, pivoting, or linear movement of a part of the tool.
Once the tool is attached to (e.g., in contact with) a tool driver in the arm, operator co
mmands may cause movements and activate functions of the attached tool. [0003] Robot joints are driven in a variety of techniques.
In many examples, each degree of freedom corresponds to a joint and corresp
onding actuator and motor. Some joints are directly driven by a drive train such th
at a single motor drives the joint in two directions. In this example, there is a direct corre
lation between motor position and joint position. For any given motor position, there
is only one corresponding joint position. [0004] Other drive techniques may involve multiple motors to
drive a joint. In this example, the motors may cooperate to provide a certa
in joint position. That is, there are multiple possible positions for the two motors that
cooperate to provide the desired joint position. Additional benefits may be realized b
y selecting from among the multiple possible motor positions. SUMMARY [0005] Disclosed herein is a robotically‐assisted surgical
electro‐mechanical system designed for surgeons to perform minimally‐in
vasive surgery. A suite of compatible tools can be attached/detached from an ins
trument driver mounted to the distal end of a robotic arm, enabling the surgeon t
o perform various surgical tasks. The instrument drivers can provide intracorporeal access t
o the surgical site, mechanical actuation of compatible tools through a sterile inter
face, and communication with compatible tools through a sterile interface and user
touchpoints. [0006] One example robotic method includes providing a redun
dant degree of freedom (DoF) for an end effector joint of one DoF
by driving the joint with two actuators, calculating a position displacement of the
joint to effect a desired end effector movement in response to an input command, c
alculating a first movement of the two actuators based on the position displacement
of the joint and a second movement of the two actuators based on a second con
trol objective in a null space corresponding to the redundant DoF, and driving the
joint according to the first movement and the second movement to effect the desir
ed end effector movement while accomplishing the second control objective in t
he null space. [0007] One example apparatus to provide a control objective
using a null space of a redundant degree of freedom of a surgical tool in
cludes a tool driver including a plurality of actuators providing a redundant degree o
f freedom (DoF) for an end effector joint of one DoF and one or more processors. The o
ne or more processors are configured to provide a redundant degree of freedom
(DoF) for an end effector joint of one DoF by driving the joint with two actuators, ca
lculate a position displacement of the joint to effect a desired end effector movement in
response to an input command, calculate a first movement of the two actuators base
d on the position displacement of the joint and a second movement of the two actuator
s based on a second control objective in a null space corresponding to the redun
dant DoF, and generate a joint command for the joint according to the first movemen
t and the second movement to effect the desired end effector movement while accomp
lishing the second control objective in the null space. [0008] One example non‐transitory computer readable medium
including instructions to cause one or more processors to perf
orm identifying a redundant degree of freedom (DoF) for an end effector joint of one
DoF by driving the joint with a plurality of actuators, calculating a position displacement of
the joint to effect a desired end effector movement in response to an input command, c
alculating a first movement of the two actuators based on the position displacement
of the joint and a second movement of the two actuators based on a second con
trol objective in a null space corresponding to the redundant DoF, and driving the
joint according to the first movement and the second movement to effect the desir
ed end effector movement while accomplishing the second control objective in t
he null space. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1 illustrates an example operating room environm
ent including a surgical robotic system. [0010] FIG. 2 illustrates an example surgical tool. [0011] FIG. 3 illustrates a mapping for the tool driver to
the surgical tool. [0012] FIG. 4 illustrates a view of a drive system for th
e surgical tool. [0013] FIG. 5 illustrates another view of a drive system f
or the surgical tool. [0014] FIG. 6 illustrates a firing subsystem of the drive
system for the surgical tool. [0015] FIG. 7 illustrates an articulation subsystem of the
drive system for the surgical tool. [0016] FIG. 8 illustrates a top down view of the articulat
ion subsystem. [0017] FIG. 9 illustrates a roll subsystem of the drive sy
stem for the surgical tool. [0018] [0019] FIG. 10 illustrates a closure subsystem of the drive
system for the surgical tool. [0020] FIG. 11 illustrates a manual knob for the closure s
ubsystem. [0021] FIG. 12 illustrates a controller for the tool driver
and/or surgical tool. [0022] FIG. 13 illustrates a representation of the redundanc
y of the articulation joint. [0023] FIG. 14 illustrates a representation of the redundanc
y of the closure joint. [0024] FIG. 15 illustrates an example control objective usin
g the null space of the articulation subsystem. [0025] FIG. 16 illustrates a flow chart for an embodiment
of the control system. DETAILED DESCRIPTION [0026] The following embodiments relate to control systems f
or an endoscopic surgical instrument. Endoscopic surgical instruments ty
pically include a long, thin tube that is inserted directly into the body to observe
or otherwise perform a task on an internal organ or tissue. Endoscopic surgical instrume
nts may be inserted through an incision or other opening of the body such as the
mouth or anus. Endoscopic surgical instruments may be suitable for precise placement of
a distal end effector at a desired surgical site through a cannula. These distal end ef
fectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effec
t (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene thera
py delivery device, and energy device using ultrasound, radio frequency (RF) treatmen
t, lasers, or others). [0027] As discussed in more detail below, the endoscopic in
strument may include multiple joints, with at least one joint having a r
edundant degree of freedom. The redundant degree of freedom means that the number of
motors or actuators for the joint is greater than the number of axes for the j
oint. In most scenarios, the number of axes for a joint is one. For a joint without a re
dundant degree of freedom, there may be a direct (1:1) relationship or other linear relations
hip between the motor position and the joint position. However, for a joint with a red
undant degree of freedom, there is more than one position for the motors or actuators
that provides any given joint position. [0028] A relationship for positions of the motors or actuat
ors and the joint position may be described algebraically. A solution o
f the relationship is provided by the null space. The null space defines the possibilities
for the positions of the motors or actuators while still maintaining the desired joint p
osition. Within this null space, the positions of the motors or actuators can be changed
to optimize another control objective. The following control systems select positi
ons of the motors or actuators within the null space so that both the desired posi
tion of the joint and at least one additional control objective is achieved. [0029] For example, the following embodiments described appar
atus and methods for null space control for a surgical tool
s articulation joint and/or closure joint. In the case of the articulation joint, a minimum am
ount of tension is maintained for the articulation motors to prevent slack in the joint mo
tion and maintain a prescribed level of pre‐tension throughout the total use of the sur
gical instrument. Thus, the additional control objective achieved is the prescribed level of
pre‐tension. The prescribed level of pre‐tension is maintained while also providing the
desired joint position. [0030] In the case of the closure joint, the system guaran
tees two closure motors could help each other to deliver large amount of re
quired joint level torque. Thus, the additional control objective achieved is the large am
ount of joint torque. The joint torque is maintained while also providing the desired
joint position. [0031] FIG. 1 is a diagram illustrating an example operatin
g room environment with a surgical robotic system 100. As shown in FIG
. 1, the surgical robotic system 100 comprises a user console 110, a control tower 130,
and a surgical robot 120 having one or more surgical robotic arms 122 mounted on a surg
ical platform 124 (e.g., a table or a bed etc.), where surgical tools with end effectors a
re attached to the distal ends of the robotic arms 122 for executing a surgical procedure.
The robotic arms 122 are shown as table‐mounted, but other configurations, the robotic
arms may be mounted in a cart, a ceiling, a sidewall, or other suitable support surfac
es. [0032] Generally, a user, such as a surgeon or other opera
tor, may be seated at the user console 110 to remotely manipulate the robo
tic arms 122 and/or surgical instruments (e.g., teleoperation). The user console 11
0 may be located in the same operation room as the robotic system 100, as shown
in FIG. 1. In other environments, the user console 110 may be located in an adjacent
or nearby room, or teleoperated from a remote location in a different building, city
, or country. The user console 110 may comprise a seat 112, pedals 114, one or more handhe
ld user interface devices (UIDs) 116, and an open display 118 configured to display,
for example, a view of the surgical site inside a patient. As shown in the exemplary us
er console 110, a surgeon sitting in the seat 112 and viewing the open display 118 may
manipulate the pedals 114 and/or handheld user interface devices 116 to remotely contr
ol robotic arms 122 and/or surgical instruments mounted to the distal ends of t
he arms 122. [0033] In some variations, a user may also operate the sur
gical robotic system 100 in an “over the bed” (OTB) mode, in which
the user is at the patient’s side and simultaneously manipulating a robotically‐driven tool/
end effector attached thereto (e.g., with a handheld user interface device 116 hel
d in one hand) and a manual laparoscopic tool. For example, the user’s left han
d may be manipulating a handheld user interface device 116 to control a robotic surgi
cal component, while the user’s right hand may be manipulating a manual laparoscopic tool.
Thus, in these variations, the user may perform both robotic‐assisted minimally inv
asive surgery (MIS) and manual laparoscopic surgery on a patient. [0034] An end effector may be configured to execute a surg
ical operation such as cutting, grasping, poking, or energy emission. The su
rgical tool may be manipulated manually, robotically, or both, during the surgery. F
or example, the surgical tool may be a tool used to enter, view, or manipulate an intern
al anatomy of the patient. In an embodiment, the surgical tool is a grasper that can
grasp tissue of the patient. The surgical tool may be controlled manually, directly by
a hand of a bedside operator or it may be controlled robotically, via sending electronic
commands to actuate movement. [0035] During an exemplary procedure or surgery, the patient
is prepped and draped in a sterile fashion to achieve anesthesia. I
nitial access to the surgical site may be performed manually with the robotic system 100 in a
stowed configuration or withdrawn configuration to facilitate access to the s
urgical site. Once the access is completed, initial positioning and/or preparation of t
he robotic system may be performed. During the procedure, a surgeon in the us
er console 110 may utilize the pedals 114 and/or user interface devices 116 to mani
pulate various end effectors and/or imaging systems to perform the surgery. Manual assist
ance may also be provided at the procedure table by sterile‐gowned personnel, who may
perform tasks including but not limited to, retracting tissues, or performing manual
repositioning or tool exchange involving one or more robotic arms 122. Nonsterile p
ersonnel may also be present to assist the surgeon at the user console 110. When th
e procedure or surgery is completed, the robotic system 100 and/or user console 110 may
be configured or set in a state to facilitate one or more post‐operative procedures, in
cluding but not limited to, robotic system 100 cleaning and/or sterilization, and/or healt
hcare record entry or printout, whether electronic or hard copy, such as via the us
er console 110. [0036] In some aspects, the communication between the surgic
al robot 120 and the user console 110 may be through the control tow
er 130, which may translate user input from the user console 110 to robotic control
commands and transmit the control commands to the surgical robot 120. The control towe
r 130 may also transmit status and feedback from the robot 120 back to the user c
onsole 110. The connections between the surgical robot 120, the user console 110
and the control tower 130 may be via wired and/or wireless connections, and may be pr
oprietary and/or performed using any of a variety of data communication protocols. An
y wired connections may be optionally built into the floor and/or walls or ceil
ing of the operating room. The surgical robotic system 100 may provide video output to one
or more displays, including displays within the operating room, as well as remote display
s accessible via the Internet or other networks. The video output or feed may also b
e encrypted to ensure privacy and all or portions of the video output may be saved t
o a server or electronic healthcare record system. [0037] Prior to initiating surgery with the surgical robotic
system, the surgical team can perform the preoperative setup. During the
preoperative setup, the main components of the surgical robotic system (table 124
and robotic arms 122, control tower 130, and user console 110) are positioned in
the operating room, connected, and powered on. The surgical platform 124 and robotic ar
ms 122 may be in a fully‐stowed configuration with the arms 122 under the surgical p
latform 124 for storage and/or transportation purposes. The surgical team can extend
the arms from their stowed position for sterile draping. [0038] After draping, the arms 122 can be partially retract
ed until needed for use. A number of conventional laparoscopic steps may be p
erformed including trocar placement and installation. For example, each sleeve
can be inserted with the aid of an obturator, into a small incision and through the bod
y wall. The sleeve and obturator allow optical entry for visualization of tissue layer
s during insertion to minimize risk of injury during placement. The endoscope is typically p
laced first to provide hand‐held camera visualization for placement of other trocars.
[0039] After insufflation, if required, manual instruments ca
n be inserted through the sleeve to perform any laparoscopic steps by hand
. Next, the surgical team may position the robotic arms 122 over the patient and
attach each arm 122 to its corresponding sleeve. The surgical robotic system 100
has the capability to uniquely identify each tool (endoscope and surgical instruments
) as soon as it is attached and display the tool type and arm location on the open
or immersive display 118 at the user console 110 and the touchscreen display on the contr
ol tower 130. The corresponding tool functions are enabled and can be activated usin
g the master UIDs 116 and foot pedals 114. The patient‐side assistant can attach a
nd detach the tools, as required, throughout the procedure. The surgeon seated at the
user console 110 can begin to perform surgery using the tools controlled by two ma
ster UIDs 116 and foot pedals 114. The system translates the surgeon’s hand, wrist, an
d finger movements through the master UIDs 116 into precise real‐time movements of
the surgical tools. Therefore, the system constantly monitors every surgical maneuver of
the surgeon and pauses instrument movement if the system is unable to preci
sely mirror the surgeon's hand motions. In case the endoscope is moved from one ar
m to another during surgery, the system can adjust the master UIDs 116 for instrument
alignment and continue instrument control and motion. The foot pedals 114 m
ay be used to activate various system modes, such as endoscope control and various
instrument functions including monopolar and bipolar cautery, without involving surge
on's hands removed from the master UIDs 116. [0040] The surgical platform 124 can be repositioned intraop
eratively. For safety reasons, all tooltips should be in view and under a
ctive control by the surgeon at the user console 110. Instruments that are not under act
ive surgeon control are removed, and the table feet are locked. During table motion,
the integrated robotic arms 122 may passively follow the table movements. Audio and visua
l cues can be used to guide the surgery team during table motion. Audio cues may inc
lude tones and voice prompts. Visual messaging on the displays at the user console
110 and control tower 130 can inform the surgical team of the table motion status.
[0041] FIG. 2 illustrates an example surgical tool assembly
200. The surgical tool assembly 200 includes a surgical tool 240 to a tool
driver 230. The surgical tool 240 is connected to end effector 222 via shaft 233. Additio
nal, different, or fewer components may be included. [0042] The surgical tool assembly 200 may be an endoscopic
surgical instrument. The surgical tool assembly 200 may be an endocutter.
An endocutter may be configured to divide and seal tissue. Put another way, an endo
cutter may be configured to cut and staple tissue with motion provided by an articulation
joint. The endocutter may be used to cut and staple tissue in a variety of surgical
procedures, including bariatric, thoracic, colorectal, gynecologic, urologic, and general surgery.
Common clinical use scenarios include reshaping organs, the removal or repair of o
rgans, tissue fixation, dissection, or the creation of anastomoses (or any combination of t
hese). FIG. 2 is an illustration of a subsystem or a part of the surgical robotic system
100, for detecting engagement of a surgical tool 240 to a tool driver 230 of a surgic
al robotic arm 122. The surgical robotic arm 122 may be one of the surgical robotic arms of
surgical robotic system 100 illustrated and discussed with respect to FIG. 1. Th
e control unit 210 may be part of for example the control tower in FIG. 1. As discussed i
n more detail herein, the engagement may be detected by control unit 210 based on one o
r more rotary motor operating parameters of one or more actuators (e.g., actuator
238‐j) in the tool driver 230. [0043] There is a tool driver 230 to which different surgi
cal tools (e.g., surgical tool 240, as well as other detachable surgical tools
for rotation of an endoscope camera, pivoting of a grasper jaw, or translation of a need
le) may be selectively attached (one at a time.) This may be done by for example a human
user holding the housing of the surgical tool 240 in her hand and moving the latter
in the direction of arrow 280 shown until the outside surface of the surgical tool 240
in which there are one or more tool disks (e.g., tool disk 244‐i described below) comes
into contact with the outside surface of the tool driver 230 in which there are one or
more drive disks (e.g., drive disk 234‐j described below). The one or more tool disks and/or
one or more drive disks may be implemented by pucks, which may be formed of plastic
or another durable material. In the example shown, the tool driver 230 is a segment
of the surgical robotic arm 122 at a distal end portion of the surgical robotic arm 122.
A proximal end portion of the arm is secured to a surgical robotic platform, such as a s
urgical table that shown in FIG. 1 described above. [0044] The control system is described in detail with respe
ct to FIG. 12 below. By of introduction to the control system, the control s
ystem of FIG. 12 includes a control unit 210 configured to control motion of the various
motorized joints in the surgical robotic arm 122 (including the drive disks 234) thro
ugh which operation of end effector 222 (its position and orientation as well as its su
rgical function such as opening, closing, cutting, applying pressure, etc.) which mimics that o
f a user input device is achieved. This is achieved via a mechanical transmission in th
e surgical tool 240, when the surgical tool 240 has been engaged to transfer force or torq
ue from the tool driver 230. The control unit 210 may be implemented as a programmed
processor, for example as part of the control tower 130 of FIG. 1. It may respond
to one or more user commands received via a local or remote user input (e.g., jo
ystick, touch control, wearable device, or other user input device communicating via console
computer system.) Alternatively, the control unit 210 may respond to one or more au
tonomous commands or controls (e.g., received form a trained surgical machine learn
ing model that is being executed by the control unit 210 or by the console computer sys
tem), or a combination thereof. The commands dictate the movement of robotic arm 122 and
operation of its attached end effector 222. [0045] An end effector 222 may be any surgical instruments,
such as jaws, a cutting tool, an endoscope, spreader, implant tool, s
tapler, etc. FIG. 2 includes an endocutter having a combination of two or more of t
hese instruments such as a cutting tool, jaws, and stapler. Different surgical tools eac
h having different end effectors can be selectively attached (one at a time) to robotic arm
122 for use during a surgical or other medical procedure. [0046] The robotic arm includes a tool driver 230, in whic
h there are one or more actuators, such as actuator 238‐j. Each actuator ma
y be a linear or rotary actuator that has one or more respective electric motors (e.g., a
brushless permanent magnet motor) whose drive shaft may be coupled to a respective dr
ive disk 234‐j through a transmission (e.g., a gear train that achieves a given gear redu
ction ratio). The tool driver 230 includes one or more drive disks 234 that may be arranged o
n a planar or flat surface of the tool driver 230, wherein the figure shows several such dr
ive disks that are arranged on the same plane of the flat surface. Each drive disk (e.
g., drive disk 234‐j) is exposed on the outside surface of the tool driver 230 and is desig
ned to mechanically engage (e.g., to securely fasten via snap, friction, or other mating
features) a mating tool disk 244‐j of the surgical tool 240, to enable direct torque trans
fer between the two. This may take place once for example a planar or flat surface of
the surgical tool 240 and corresponding or mating planar or flat surface of th
e tool driver 230 are brought in contact with one another. [0047] Furthermore, a motor driver circuit (for example, ins
talled in the tool driver 230 or elsewhere in the surgical robotic arm
122) is electrically coupled to the input drive terminals of a constituent motor of one
or more of the actuators 238. The motor driver circuit manipulates the electrical power
drawn by the motor in order to regulate for example the speed of the motor or its
torque, in accordance with a motor driver circuit input, which can be set or controlled
by control unit 210, which results in the powered rotation of the associated drive disk (e
.g., drive disk 234‐j). [0048] When the mating drive disk 234‐j is mechanically e
ngaged to a respective tool disk 244‐j, the powered rotation of the drive
disk 234‐j causes the tool disk 244‐j to rotate, e.g., the two disks may rotate as one, ther
eby imparting motion on, for example, linkages, gears, cables, chains, or other transmission
devices within the surgical tool 240 for controlling the movement and operation of the en
d effector 222 which may be mechanically coupled to the transmission device. [0049] Different surgical tools may have different numbers o
f tool disks based on the types of movements and the number of degrees of
freedom in which the movements are performed by their end effectors, such
as rotation, articulation, opening, closing, extension, retraction, applying press
ure, etc. [0050] Furthermore, within the surgical tool 240, more than
one tool disk 244 may contribute to a single motion of the end effect
or 222 to achieve goals such as load sharing by two or more motors that are driving the
mating drive disks 234, respectively. In another aspect, within the tool driver 230, there
may be two or more motors whose drive shafts are coupled (via a transmission) to rot
ate the same output shaft (or drive disk 234), to share a load. [0051] In yet another aspect, within the surgical tool 240,
there may be a transmission which translates torque from two drive d
isks 234 (via respective tool disks 244) for performing complementary actions in the same
degree of freedom, e.g., a first drive disk 234‐j rotates a drum within the housing
of the surgical tool 240 to take in one end of a rod, and a second drive disk 234‐i rota
tes another drum within the housing of the surgical tool 240 to take in the other end of
the rod. As another example, the extension and the shortening of an end effector alon
g a single axis may be achieved using two tool disks 234‐i, 234‐j, one to perfor
m the extension and another to perform the retraction. This is in contrast to an effector
that also moves in one degree of freedom (e.g., extension and shortening longitudinally
along a single axis of movement) but that only needs a single tool disk to control
its full range of movement. As another example, an effector that moves in multiple degrees
of freedom (e.g., such as a wristed movement, movement along multiple axes, activation of
an energy emitter in addition to end effector movement, etc.) may necessitate the
use of several tool disks (each being engaged to a respective drive disk). In anothe
r type of surgical tool 240, a single tool disk 244 is sufficient to perform both extensio
n and retraction motions, via direct input (e.g., gears). As another example, in the case
of the end effector 222 being jaws, two or more tool disks 244 may cooperatively control
the motion of the jaws, for load sharing, as discussed in greater detail herein. [0052] In yet another aspect, within the surgical tool 240,
there may be a transmission which translates torque from two drive d
isks 234 (via respective tool disks 244) for performing complimentary actions in the same
degree of freedom, e.g., a first drive disk 234‐i rotates a drum within the housing
of the surgical tool 240 to take in one end of a cable, and a second drive disk 234‐j ro
tates another drum within the housing of the surgical tool 240 to take in the other end of
the cable. As another example, the extension and the shortening of an end effector alon
g a single axis may be achieved using two tool disks 234‐i, 234‐j, one to perfor
m the extension and another to perform the retraction, for example via different cables. Thi
s is in contrast to an effector that also moves in one degree of freedom (e.g., extension and
shortening longitudinally along a single axis of movement) but that only needs a sing
le tool disk to control its full range of movement. As another example, an effector that moves
in multiple degrees of freedom (e.g., such as a wristed movement, movement along mu
ltiple axes, activation of an energy emitter in addition to end effector movement,
etc.) may necessitate the use of several tool disks (each being engaged to a respecti
ve drive disk). In another type of surgical tool 240, a single tool disk 244 is suffic
ient to perform both extension and retraction motions, via direct input (e.g., gears). A
s another example, in the case of the end effector 246 being jaws, two or more tool disks
244 may cooperatively control the motion of the jaws, for load sharing, as discussed
in greater detail herein. [0053] FIG. 3 illustrates a mapping for the tool driver 23
0 to the surgical tool 240. FIG. 3 illustrates rotary device assignments or mappi
ng for tool disks R1‐R6. In this example, tool disk R1 is assigned to a cutting inst
rument such as a knife. As the tool disk R1 is moved in one direction (e.g., clockwise) the
cutting instrument advances, and as the tool disk R1 is moved in a second direction (e
.g., counterclockwise) the cutting blade retracts. [0054] Tool disks R2 and R4 are assigned to the articulati
on joint. The tool disks R2 and R4 may be connected to the end effector 222
in an antagonistic pairs, that is, when one cable of the antagonistic pair is actuated
or tensioned, while the other cable is loosened, the jaw will rotate in one direction. When
only the other cable is tensioned, the jaw will rotate in an opposite direction. One d
irection (e.g., clockwise) corresponds to articulation of the end effector 222 to the left
, and the other direction (e.g., counterclockwise) corresponds to the articulation of t
he end effector to the right. Articulation may be a change in orientation of the
end effector 222 at an axis transverse to the longitudinal axis of the shaft of the instru
ment. This articulated positioning permits the clinician to more easily engage tissue i
n some instances. In addition, articulated positioning advantageously allows an endosc
ope to be positioned behind the end effector without being blocked by the instrument
shaft. [0055] Tool disk R3 is mapped to the roll axis of the en
d effector. The tool disk R3 may be coupled to one or more gears that drive the
wrist to rotate about the roll axis. The rotation of the tool disk R1 in a first direct
ion with respect to the plane of the tool disks (e.g., clockwise) may cause rotation of the
roll axis of the end effector in the same direction (e.g., clockwise) and rotation of the tool
disk R1 in a second direction with respect to the plane of the tool disks (e.g., cou
nter clockwise) may cause rotation of the roll axis of the end effector in the same direction
(e.g., counter clockwise). [0056] Tool disks R5 and R6 are assigned to the closure d
evice or jaw. For example, the one of the opposing jaws may be assign
ed to tool disk R5 and tool disk R6 operation in one direction for opening the jaw (i.e.
, increasing the angle between the opposing jaws) and another direction for closing the jaw (i.e., decreasing the angle between the opposing jaws). [0057] In some embodiments, when surgical tool 240 is first
attached to or installed on tool driver 230 such that the tool dis
ks are brought substantially into coplanar and coaxial alignment with corresponding driv
e disks (though the tool and drive disks are perhaps not yet successfully engaged)
, control unit 210 initially detects the type of the surgical tool 240. In one embodimen
t, surgical tool 240 has an information storage unit 242, such as a solid state
memory, radio frequency identification (RFID) tag, bar code (including two‐d
imensional or matrix barcodes), etc., that identifies its tool or end effector information,
such as one or more of identification of tool or end effector type, unique tool or end e
ffector ID, number of tool disks used, location of those tool disks being used (e.g., from
a total of six possible tool disks 244‐e, f, g, h, i, j), type of transmission for the tool
disks (e.g., direct drive, cable driven, etc.), what motion or actuation a tool disk imparts on the
end effector, one or more tool calibration values (e.g., a rotational position of th
e tool disk as determined during factor testing/assembly of the tool), whether motion of the
end effector is constrained by a maximum or minimum movement, as well as other tool
attributes. In one embodiment, the information storage unit 242 identifies minimal i
nformation, such as a tool ID, which control unit 210 may use to perform a lookup of th
e various tool attributes. [0058] The tool driver 230 may include a communication inte
rface 232 (e.g., a memory writer, a near field communications, near fiel
d communication (NFC), transceiver, RFID scanner, barcode reader, etc.) to r
ead the information from the information storage unit 242 and pass the information
to control unit 210. Furthermore, in some embodiments, there may be more than one inf
ormation storage unit in surgical tool 240, such as one information storage unit assoc
iated with each tool disk 244. In this embodiment, tool driver 230 may also include a corre
sponding sensor for each possible information storage unit that would be present in a
given tool. [0059] After surgical tool 240 is attached with tool driver
230, such that tool disks are brought into alignment and are superimposed on c
orresponding drive disks (although not necessarily mechanically engaged), and a
fter the tool disk information is obtained, e.g., read by control unit 210, the contro
l unit 210 performs an engagement process to detect when all of the tool disks that
are expected to be attached to respective drive disks are mechanically engaged with
their respective drive disks (e.g., their mechanical engagement has been achieved, or the
tool driver 230 is now deemed engaged with the tool). That is, attaching the surgi
cal tool 240 with the tool driver 230 does not necessarily ensure the proper mating needed
for mechanical engagement of tool disks with corresponding drive disks (e.g., due
to misalignment of mating features). The engagement process may include activating one or
more motors of an actuator (e.g., actuator 238‐j) that drives a corresponding
drive disk 234‐j. Then, based on one or more monitored motor operating parameters of the actu
ator 238‐j, while the latter is driving the drive disk 234‐j, the mechanical engage
ment of the tool disk 244‐i with a drive disk 234‐j can be detected. This process may
be repeated for every drive disk 234 (of the tool driver 230) that is expected to be cu
rrently attached to a respective tool disk 244 (e.g., as determined based on the tool disk inf
ormation obtained for the particular surgical tool 240 that is currently attached.) [0060] Upon detecting that a particular type of surgical to
ol 240 has been attached with the tool driver 230, the control unit
210 activates one or more actuators (e.g., motors) of the tool driver 230 that have bee
n previously associated with that type of surgical tool 240. In some embodiments, each actu
ator that is associated with a corresponding drive disk 234 of surgical tool 240 ma
y be activated simultaneously, serially, or a combination of simultaneous and serial
activation. [0061] FIGS. 4‐11 illustrate a drive system for the surgi
cal tool 240. FIG. 4 illustrates a left side view of a drive system for
the surgical tool and FIG. 5 illustrates a right side view of the drive system. The drive syst
em includes a fire subsystem 401, an articulation subsystem 402, a roll subsystem 403, and
a closure subsystem 405. Additional, different, or fewer components may be inc
luded. [0062] FIG. 6 illustrates the firing subsystem 401 of the
drive system for the surgical tool. The fire subsystem 401 includes a fir
ing shaft 410 that is rigidly connected to tool disk R1 (firing input puck 411). The firing
shaft 410 may be coupled to and support the firing input puck 411 such that the fir
ing input puck 411 is mounted to the firing shaft 410. Also mounted to the firing shaft
410 may be a driving gear 476 (firing shaft driving gear). The driving gear 476 imparts mo
tion and torque onto driven gear 473. The driven gear 473 is part of the drive trai
n to the drive bar 470 and also facilitates the bailout mechanism. The rest of the drive train
to the drive bar 470 includes a gear reduction set including gear 474 driven by the shaft
of the driven gear 473 and a pinion gear 475 that runs along the rack of the drive bar
470. [0063] The bailout mechanism includes a manual bailout input
cylinder 471. The user input device 472 fits over the manual bailout
input cylinder 471, or is otherwise coupled to the manual bailout input cylinder 471. Ro
tating the manual bailout input cylinder 471 through user input a portion of the dr
ive train out of engagement with the drive bar 470. This manually overrides the movement
of the drive bar 470 from the tool driver 230. [0064] FIG. 7 illustrates the articulation subsystem 402 of
the drive system for the surgical tool. FIG. 8 illustrates a top down view o
f the articulation subsystem 402. The articulation subsystem 402 includes a left articulatio
n shaft 440 and a right articulation shaft 420. The left articulation shaft 440 is couple
d to and driven by tool disk R4 (left articulation input puck 441). The right articulation
shaft 420 is coupled to and driven by tool disk R2 (right articulation input puck 421). Th
e left articulation shaft 440 includes a left pinion gear 444 connected to the articulation j
oint. The right articulation shaft 420 includes a right pinion gear 420 connected to the a
rticulation joint. [0065] FIG. 8 provides more detail of the drive of the ar
ticulation joint. Right pinion gear 424 drives right rack 425 connected to
the articulation joint. Left pinion gear 444 drives left rack 445 connection to the articulat
ion joint. The right rack 425 (e.g., first rigid rod) moves the right articulation arm 426 and
ultimately causes the right protrusion 427 of the articulation joint to rotate about the c
enter of the articulation disk. Likewise, the left rack 445 (e.g., second rigid rod) moves
the left articulation arm 446 and ultimately causes the left protrusion 447 of the art
iculation joint to rotate about the center of the articulation disk. Movement of the rig
ht rack 425 and/or the left rack 445 applies torques at the wrist to create articulation
movement. [0066] FIG. 9 illustrates the roll subsystem 403 of the dr
ive system for the surgical tool. The roll subsystem 403 includes a roll shaft
430. The roll shaft 430 is coupled to and driven by tool disk R3 (roll input puck 431). The
roll input puck 431 is coupled to the roll shaft 430 along with worm gear 435 in order to dri
ve roll gear 439. The roll gear 439 provides the motion to the roll joint in either the
clockwise or counterclockwise direction depending on the rotation of the tool disk
R3. [0067] FIG. 10 illustrates a closure subsystem 405 of the
drive system for the surgical tool. The closure subsystem 405 includes a
left closure shaft 450 and a right closure shaft 460. The left closure shaft 450 is co
upled to and driven by tool disk R5 (left closure input puck 451). The right closure shaft 460
is coupled to and driven by tool disk R6 (right closure input puck 461). A left drive gea
r 452 is coupled to the left closure shaft 450 and a right drive gear 462 is coupled to the
right closure shaft 460. The left drive gear 452 and the right drive gear 462 cooperate to
drive closure gear 465, which operates the closure joint. [0068] A cam cam/yoke mechanism 459 translates the rotary i
nput from the left closure input puck 451 and the right closure input
puck 461 to a linear output. A variable mechanical advantage is provided by the cam/yoke mech
anism 459 at a function of its angular position. For example, the cam/yoke mechanism
459 may include a push pull rod that distally includes a pin 467 that slides on
a slot 468, creating the open and close jaw motion. [0069] FIG. 11 illustrates a manual knob 481 for the closu
re subsystem 405. One or more coupling gears 466 couple the drive closure
gear 465 to the manual know 481. The manual knob 481 includes a surface or handle fo
r receiving a user’s grip to rotate the manual knob 481, causing rotation of the left d
rive gear 452 and/or the right drive gear 462, to manually operate the closure joint. [0070] FIG. 12 illustrates an example of the surgical tool
240 that utilizes six tool disks, such as tool disks 244‐e, f, g, h, i, j,
arranged in a coplanar fashion on a mating surface of its housing. Any arrangement of tool disk
s 244‐e, f, g, h, i, j, may correspond to tool disks R1‐R6, in general, or specifically f
iring input puck 411, right articulation input puck 421, roll input puck 431, left articulati
on input puck 441, left closure input puck 451, and right closure input puck 461 described
previously. Each tool disk contributes to at least a portion of the movement a
nd/or activation of end effector 222. Upon detecting the attachment of surgical tool 240 w
ith tool driver 230 (e.g., joining of mating surfaces of the respective housings), control
unit 210 (or its processor 312 while executing instructions stored in memory 314 as) perfo
rms a process which determines that the corresponding drive disks, such as drive di
sks 234 e, f, g, h, i, j, are to be turned (a corresponding actuator 238 is activated) to perfor
m the engagement process. [0071] In some embodiments, the motor operating parameters m
onitored by the control unit 210 (via sensors 236) are interpreted t
o mean successful mechanical engagement of a tool disk with a drive disk. The c
ontrol unit 210 is in communication with and receives sensor data from sensor 236 in an
example sensor array including any combination of a presence sensor 341, a torque senso
r 342, a position sensor 343, an electrical sensor 345, an optical sensor 347, and a
force sensor 348. The sensor array may include separate sensors for different degrees of
freedom of the surgical tool (e.g., closure joint, articulation joint, roll joint, or oth
er operation of the surgical tool). That is, the sensor array, or one or more sensors thereof, m
ay be repeated for multiple tool disks 244 in the tool driver 230. [0072] The measurements may include measurements of torque a
pplied by the actuator 238‐j as measured by the torque sensor 34
2 or the force sensor 348, measurements of current by the electrical sensor 345
supplied to a motor of the actuator 238‐j when attempting to drive the actuato
r to move at a certain velocity (e.g., where the sensor 236‐j may include a current sensi
ng resistor in series with a motor input drive terminal), measurements of electrical impe
dance by the electrical sensor 345 as seen into the input drive terminals of the motor
of the actuator 238 when attempting to drive the motor to move at a certain velocity (
e.g., where the sensor 236‐j may also include a voltage sensing circuit to measure voltage
of the motor input drive terminal), speed of the actuator 238‐j (e.g., where the optic
al sensor 347 may include a position encoder on an output shaft of the actuator 238‐j
or on a drive shaft of the motor), as well as other parameters referred to here as motor
operating parameters. The measurements may include presence data from the prese
nce sensor 341, implied from any sensor in the sensor array 236, or determined f
rom the interaction between the information storage unit 242 and the communication in
terface 232. The position sensor 343 is illustrated separately but may be implemented
using a combination of the presence sensor 341, the torque sensor 342, the elec
trical sensor 345, the optical sensor 347, and the force sensor 348. In one example, addi
tional sensors of the same type may be used for the position sensor 343. [0073] While monitoring the one or more motor operating par
ameters of a particular actuator, when one or more of these param
eters satisfies (e.g., meets or reaches) a predetermined, condition or threshold, the
detection of such a situation can be interpreted by control unit 210 as a mechanical
engagement event. Note that satisfying the predetermined condition may for example
mean that the monitored operating parameter exhibits certain changes, as per
the threshold, relative to an operating parameter of another motor that is part of
the same actuator 238‐j or that is part of another actuator 238‐i which his being con
trolled by the control unit 210 simultaneously during the engagement detection process.
[0074] In some embodiments, detection of certain motor opera
ting parameters during operation of the actuator 238‐j, such as on
e or more of i) torque that satisfies (e.g., rises and reaches) a torque threshold, ii) mo
tor current that satisfies (e.g., rises and reaches) a current threshold, iii) impedance that dro
ps below an impedance threshold, iv) motor speed dropping below a motor velocity thre
shold, or a combination thereof, are used by control unit 210 to determine that mech
anical engagement of tool disk 244‐j to drive disk 234‐j has occurred. [0075] The control unit 210 including its programmed process
or 312 may be integrated into the surgical robotic system 100 (FIG.
1) for example as a shared microprocessor and program memory within the control
tower 130. Alternatively, the control unit 210 may be implemented in a remote com
puter such as in a different room than the operating room, or in a different building
than the operating arena shown in FIG. 1. Furthermore, control unit 210 may also inclu
de, although not illustrated, user interface hardware (e.g., keyboard, touch‐screen, mic
rophones, speakers) that may enable manual control of the robotic arm and its at
tached surgical tool 240, a power device (e.g., a battery), as well as other component
s typically associated with electronic devices for controlling surgical robotic systems. [0076] Memory 314 is coupled to one or more processors 312
(generically referred to here as a processor for simplicity) to
store instructions for execution by the processor 312. In some embodiments, the memory is no
n‐transitory, and may store one or more program modules, including a tension control
algorithm 315 and a torque control algorithm 316, whose instructions configure th
e processor 312 to perform the tension and torque control algorithms 315 and 316 as
described herein. In other words, the processor 312 may operate under the control of
a program, routine, or the execution of instructions stored in the memory 314 a
s part of the tension control algorithm 315 and the torque control algorithm 316 t
o execute methods or processes in accordance with the aspects and features described he
rein. The memory 314 may include one or more settings, coefficient values, thr
eshold values, tolerance values, calibration values for the surgical tool 240 and/or
the tool driver 230. These values may be stored in memory 314 as a configuration file, ta
ble, or matrix. Some values in the configuration file may be provided by the user, some
may be accessed or retrieved based on identifiers of the surgical tool 240 or to
ol driver 230, and others may be set by the control unit 210. [0077] FIG. 13 illustrates a representation of the redundanc
y of the articulation joint. The articulation joint for the surgical tool
240 is driven by two motors (e.g., the motors correspond to tool disks R2 and R4). The mec
hanical structure of the two motors driving one degree of freedom indicates that there i
s a one degree of freedom null space in the articulation joint control that is orthogona
l to the articulation joint position space. In other words, the redundancy (R) is related
to the number of motors/actuators (M) and the degrees of freedom of the joint (J) su
ch that R = M ‐ J. When R is a positive nonzero number, the joint control is said to have a
redundancy, or the corresponding null space exists. When R = 1, the joint control h
as one degree of redundancy and/or one degree of null space, when R = 2 the joint ha
s two degrees of redundancy, and/or two degrees of null space and so on. The control a
ction done through this null space does not influence the articulation joint position. T
herefore, this redundancy or null space could be used to achieve extra control objecti
ves in some situations. [0078] Continuing with the example of the articulation joint
, the physical displacement of the articulation joint (θ j ) is provided by Equation 1: [0079] The relationship in Equation 1 is based on a first
position (θ m1 ) for a first actuator (e.g., corresponding to tool disk R2) and a
second actuator position (θ m2 ) for a second actuator (e.g., corresponding to tool disk R4)
, and at least one property constant including a first constant a and second constant b.
The property constant may depend on the materials of the components, the relative dim
ensions of the components, or other factors. [0080] The null space corresponding to the redundant DoF fo
r the articulation wrist joint provides a relationship between the first
movement of the two actuators and the second movement of the two actuators. For exampl
e, the relationship between the first movement of the two actuators and the second movement of the two actuators may be provided by Equation 2: [0081] In Equation 2, the null space corresponding to the
redundant DoF for the articulation wrist is described as a vector [ 1, ‐1] or [‐1, 1] T . Further, for the purpose of illustration, there may be a constraint that the joi
nt position does not change but a null space can be calculated applicable to ch
anges in the joint position as well. In the case of the surgical tool 240, the control syst
em provides a redundant degree of freedom (DoF) for the end effector articulation joint
of one DoF by driving the joint with two actuators. [0082] FIG. 14 illustrates a representation of the redundanc
y of the closure joint. In this embodiment, the closure joint uses rods and
not cables. Rods apply forces in both the pulling and pushing directions as opposed to cab
les that apply force in only the pulling direction. FIG. 14 is for illustrative purpos
es. The closure joint for the surgical tool 240 is driven by two motors (e.g., the motors
correspond to tool disks R5 and R6). There is also a mechanical structure of the two mot
ors driving one degree of freedom indicates that the there is a one degree of freedom
null space in the articulation joint control that is orthogonal to the articulation joint
position space. In other words, the redundancy (R) is a positive nonzero number. The con
trol action done through this null space does not influence the closure joint position.
Therefore, this redundancy or null space could be used to achieve extra control objecti
ves in some situations. [0083] Continuing with the example of the closure joint, th
e physical displacement of the joint (θ j ) is provided by Equation 3: [0084] The physical displacement of the joint (θ j ) is based on a first position (θ m1 ) for a first actuator and a second actuator
position (θ m2 ) for a second actuator, and a i is a constant coefficient from a tool calibra
tion process. The constant coefficient may relate to the size, shape, or positions of the
associated pucks (e.g., left closure input puck 451 and right closure input puck 461) such as
the gear ratio or kinematic ration from inputs to joints. The constant coefficient may
be related to the admittance or backlash between gears or other drive train component
s. [0085] The null space corresponding to the redundant DoF fo
r the closure joint provides a relationship between the first movement of
the two actuators and the second movement of the two actuators. For example, t
he relationship between the first movement of the two actuators and the second movement of the two actuators may be provided by Equation 2: [0086] In Equation 4, the null space corresponding to the
redundant DoF for the closure joint is described as a vector [1, ‐1] or
[1, ‐1] T . Further, for the purpose of illustration, there may be a constraint that the joi
nt position does not change but a null space can be calculated applicable to ch
anges in the joint position as well. In the case of the surgical tool 240, the control syst
em provides a redundant degree of freedom (DoF) for the end effector joint of one DoF
by driving the joint with two actuators. [0087] FIG. 15 illustrates a procedure or technique that ma
y be carried out by any of the systems described herein, for example, by a
controller, such as the control unit 210. The process may be performed by a programmed p
rocessor (also referred to here as processor or controller), configured according to
instructions stored in memory (e.g., the processor 312 and the memory 314 of FIG. 12, w
here the processor 312 is configured according to the instructions of the tensi
on control algorithm 315 and the torque control algorithm 316). Each act in FIG. 15
may refer to a separate process that may have many steps. Additional, different, or fewer
acts may be included. [0088] At act S101, motor torque is determined or calculate
d. The motor torque may be measured at the motor, corresponding drive di
sk, or corresponding tool disk R1‐ 6, which may include firing input puck 411, right a
rticulation input puck 421, roll input puck 431, left articulation input puck 441, left clo
sure input puck 451, and right closure input puck 461. The motor torque for the articulatio
n joint may be determined based on torque measured at the right articulation input puck
421 and left articulation input puck 441. The motor torque for the closure joint may be
determined based on torque measured at left closure input puck 451 and right c
losure input puck 461. [0089] Any of the described sensors may generate sensor dat
a used to determine motor torque. The torque may be directly measured by
the associated torque sensor 342 or the force sensor 348 applied to the tool di
sk or motor. The motor torque may be indirectly measured from current sensed by the electr
ical sensor 345 supplied to a corresponding motor when attempting to drive the actu
ator to move at a certain velocity (e.g., a current sensing resistor in series
with a motor input drive terminal). The motor torque may be indirectly measured by measurem
ents of electrical impedance by the electrical sensor 345 as seen into the input dr
ive terminals of the motor of the actuator 238 when attempting to drive the motor to
move at a certain velocity. The motor torque may be indirectly measured by the speed
of the tool disk or actuator (e.g., a position encoder on an output shaft of the actuat
or 238‐j or on a drive shaft of the motor). [0090] At act S103, error signal calculations are performed.
The error signal calculations are the feedback used to achieve the co
ntrol objective for the particular joint. The error signal defines the control objective
. For the articulation joint under control of the tension control algorithm 315, the co
ntrol objective may be to maintain a minimum amount of tension torque on both of the mot
ors along the null space direction in order to ensure the input gears (drive disks dri
ven by the motors on the tool driver 230, for example, including tool disks R2 and R4) a
lways engage with the output gears (driven disks for the articulation joint such as lef
t articulation input puck 441 and the right articulation input puck 421). The motor’s ini
tial engaging direction determines which direction the initial motor tension is applied,
with a torque reference τ min to be a positive number, the controller specifies that τ 1 <− τ min and τ 2 > τ min . In this example, τ min is the minimum tension, τ 1 is the first torque, and τ 2 is the second torque. It should be noted that the positive and negative signs for
min are selected to match the null space direction provided above and in FIG. 13, but
can be generalized for other cases. [0091] In the example of the articulation joint under contr
ol of the tension control algorithm 315, the error signal (e) is calcu
lated according to Equation 5: e = max (τ min + τ 1 , τ min - τ 2 ) Eq. 5 [0092] In the example of the closure joint under control o
f the torque control algorithm 316, the closure joint should deliver a la
rge amount of torque to be able to clamp the tissue in the most effective manner. This
requires two/motors, corresponding to the tool disks R5 and R6 and/or left closure in
put puck 451, and right closure input puck 461, to cooperate or work together to generate
enough torque at the joint level. However, the mechanical structure cannot guarantee tha
t and two motors work in cooperation during joint position control. To make su
re the motors could work together to deliver enough torque at the joint level, the co
ntrol objective for the closure joint may be to regulate the null space torque value to
0. To achieve this control goal, the control system applies one or more rules to calculat
e the error signal and apply output signal to general motor control. [0093] For error signal calculation in the example of the
closure joint under control of the torque control algorithm 316, in the
example of the closure joint, the error signal (e) may be calculated according to Equa
tion 6: e = ‐τ 1 + τ 2 Eq. 6 [0094] The error signal (e) is based on τ 1 is the first torque, and τ 2 is the second torque. In the example of the closure joint under c
ontrol of the torque control algorithm 316, the error signal feedback that is minimized is
the difference in motor torques associated with the two closure motors or the left
closure input puck 451, and right closure input puck 461. [0095] At act S105, the output of the controller using eit
her the tension control algorithm 315 or the torque control algorithm 316 is
projected onto the null space vector. The controller determines a projection of a
control signal for the position displacement of the joint to a vector for the null
space such that the projection represents the second control objective. For the exam
ple of the articulation joint and the tension control algorithm 315 , the output signa
l is projected with the null space vector, which is an addition of the 2‐dimension co
ntrol signal to the articulation joint position control output. As the null space control a
mount does not influence the articulation joint position control, the minimum tensi
on control for articulation motors is achieved while keep articulation joint position under
control. [0096] For the closure joint and the torque control algorit
hm 316, the second control objective is providing a certain torque at t
he closure jaw joint. The output signal is projected with the null space vector, which is a
n addition of the 2‐dimension control signal to the closure joint position control output.
As the null space control amount does not influence the closure joint position control, the
control objective that the two closure motors always help each other to deliver joi
nt level torque is achieved, while the closure joint position is also controlled as directed
by the user input. [0097] At act S107, the joint position control is performed
using the output signal projected with the null space vector. The controller
identifies or calculates an initial joint position or a change in joint position. The initial
joint position may be determined from a user input. The initial joint position may also cons
ider one or more supplemental positioning algorithms such as calibration, homing, en
gagement, or hardstop handling to determine an initial position for the joint that dev
iates from the user input. [0098] The controller modifies the initial joint position to
drive the joint according to a first movement specified by the user input and
a second movement to effect the desired end effector movement while accomplishing the
second control objective in the null space. [0099] FIG. 16 illustrates a procedure or technique that ma
y be carried out by any of the systems described herein, for example, by a
controller, such as the control unit 210. The process may be performed by a programmed p
rocessor (also referred to here as processor or controller), configured according to
instructions stored in memory (e.g., the processor 312 and the memory 314 of FIG. 12, w
here the processor 312 is configured according to the instructions of the tensi
on control algorithm 315 and a torque control algorithm 316). Additional, different,
or fewer acts than those in FIG. 16 may be performed. [00100] At act S201, the processor 312 identifies a redundan
t DoF for an end effector joint of one DoF by driving the joint with
two actuators. The redundant DoF may be provided by any surgical instrument having a join
t that is coupled to more actuators or motors that the joint has DoF. In this case, at
least one control DoF is redundant because it is in excess of the actual DoFs of the
joint. The redundant DoF means that the control space solution as more than 1 dimension, whi
ch allows for at least one additional control objective to be perform simultaneou
sly with position control for the joint. [00101] At act S203, the processor 312 calculates a position
displacement of the joint to effect a desired end effector movement in
response to an input command. The input command may be received via a local or remote
user input (e.g., joystick, touch control, wearable device, or other user input device
communicating via console computer system.) Alternatively, the control unit 210
may generate autonomous commands or controls (e.g., received form a trained
surgical machine learning model that is being executed by the control unit 210 or
by the console computer system), or a combination thereof. The commands dictate the movement
of end effector 222. [00102] For example, the processor 312 may generate one or
more actuation commands for movement of the tool disks through oper
ation of the corresponding motor or motors. The command may be a new position
of the motor (e.g., angular position) or a directional instruction (e.g., clockwis
e or counterclockwise) by a certain amount. [00103] At act S205, the processor 312 calculates a first m
ovement of the two actuators based on the position displacement of the
joint and a second movement of the two actuators based on a second control objectiv
e in a null space corresponding to the redundant DoF. The first movement is based on t
he position displacement of the joint to effect the desired end effector movement in
response to the input command in act S203. The first movement may be calculated from
a current position of the two actuators and the desired end effector movement. [00104] The second movement takes into consideration the seco
nd control objective. The second control objective may be differ
ent for different joints. For the articulation joint, the tension control algorithm 315,
may include one or more control system with a feedback loop to maintain a minimum a
mount of tension torque on both of the motors along the null space direction so tha
t the applicable drive disks (e.g., tool disks R2 and R4) that drive the left articulation i
nput puck 441 and the right articulation input puck 421. The feedback loop may provide an er
ror signal for the difference between the torque and the motors and a minimum thr
eshold. The output of the control system may be the second movement for the j
oint to realize the second objective. [00105] For the closure joint, the torque control algorithm
316 may include one or more control system with a feedback loop to maintain
an even distribution of torque on the motors along the null space direction to maintai
n a predetermined total amount of torque from the tool disks R5 and R6 and/or left c
losure input puck 451, and right closure input puck 461. The feedback loop may provid
e an error signal that is minimized is the difference in motor torques. The output of t
he control system may be the second movement for the joint to realize the second objecti
ve. [00106] At act S207, the processor 312 generates one or mor
e joint commands to drive the joint according to the first movement and
the second movement to effect the desired end effector movement while accomplishing the
second control objective in the null space. That is the first movement corresponding
to the position displacement calculated in act S203 is adjusted based on the sec
ond movement for the second control objective calculated in act S205. The joint command
includes a joint position or change in joint position that is provided to the applicable
motors or actuators. The joint command may include a first command for the first m
otor associated with the joint and a second command for the second motor associated wit
h the joint. In the case of the articulation joint, the joint command instructs the m
otors to move the tool disks R2 and R4 that drive the left articulation input puck 441
and the right articulation input puck 421. In the case of the closure joint, the joint c
ommands instructs the motors to move the tool disks R5 and R6 that drive the left closu
re input puck 451, and right closure input puck 461. [00107] Herein, the phrase “coupled with” is defined to
mean directly connected to or indirectly connected through one or more inter
mediate components. Such intermediate components may include both hardware‐ a
nd software‐ based components. Further, to clarify the use in the pendi
ng claims and to hereby provide notice to the public, the phrases “at least one o
f <A>, <B>, … and <N>“ or “at
least one of <A>, <B>, … <N>, or combination
s thereof” are defined by the Applicant in the broadest sense, superseding any other implied definiti
ons hereinbefore or hereinafter unless expressly asserted by the Applicant to the co
ntrary, to mean one or more elements selected from the group comprising A, B,
and N, that is to say, any combination of one or more of the elements A, B,
or N including any one element alone or in combination with one or more of the ot
her elements which may also include, in combination, additional elements not listed. [00108] The disclosed mechanisms may be implemented at any l
ogical and/or physical point(s), or combinations thereof, at which
the relevant information/data (e.g., message traffic and responses thereto) may be monitor
ed or flows or is otherwise accessible or measurable, including one or more gatew
ay devices, modems, computers or terminals of one or more market participants, e.g
., client computers, etc. [00109] One skilled in the art will appreciate that one or
more modules described herein may be implemented using, among other things,
a tangible computer‐readable medium comprising computer‐executable instructions (e.
g., executable software code). Alternatively, modules may be implemented as software
code, firmware code, specifically configured hardware or processors, and/or
a combination of the aforementioned. [00110] The operations of computer devices and systems shown
in Figures 1‐25 may be controlled by computer‐executable instructions
stored on a non‐transitory computer‐readable medium. For example, the exemplary
computer device or control unit 210 may store computer‐executable instructions,
generate electronic messages, extracting information from the electronic messages, e
xecuting actions relating to the electronic messages, and/or calculating values from th
e electronic messages to facilitate any of the algorithms or acts described herein. Nume
rous additional servers, computers, handheld devices, personal digital assistants, telephon
es, and other devices may also be connected to control unit 210. [00111] As illustrated in FIG. 12, the computer system may
include a processor 312 implemented by a central processing unit (CPU), a gr
aphics processing unit (GPU), or both. The processor 312 may be a component in a va
riety of systems. For example, the processor 312 may be part of a standard personal co
mputer or a workstation. The processor 312 may be one or more general processors,
digital signal processors, specifically configured processors, application specific
integrated circuits, field programmable gate arrays, servers, networks, digital c
ircuits, analog circuits, combinations thereof, or other now known or later de
veloped devices for analyzing and processing data. The processor 312 may implement a s
oftware program, such as code generated manually (i.e., programmed). [00112] The computer system includes memory 314 that can com
municate via a bus. The memory 314 may be a main memory, a static
memory, or a dynamic memory. The memory 314 may include, but is not limited to,
computer‐readable storage media such as various types of volatile and non‐volatile
storage media, including but not limited to random‐access memory, read‐only memory,
programmable read‐only memory, electrically programmable read‐only memory, e
lectrically erasable read‐only memory, flash memory, magnetic tape or disk, optical
media and the like. In one embodiment, the memory 314 includes a cache or rando
m‐access memory for the processor 312. In alternative embodiments, the memory
314 is separate from the processor 312, such as a cache memory of a processo
r, the system memory, or other memory. The memory 314 may be an external storage d
evice or database for storing data. Examples include a hard drive, compact disk (
CD”), digital video disc (“DVD”), memory card, memory stick, floppy disk, universal ser
ial bus (“USB”) memory device, or any other device operative to store data. The memory
314 is operable to store instructions executable by the processor 312. The fun
ctions, acts or tasks illustrated in the figures or described herein may be performed by
the programmed processor 312 executing the instructions stored in the memory 314.
The functions, acts or tasks are independent of the particular type of instructions se
t, storage media, processor or processing strategy and may be performed by software,
hardware, integrated circuits, firmware, micro‐code, and the like, operating alone
or in combination. Likewise, processing strategies may include multiprocessing, mult
itasking, parallel processing, and the like. [00113] The computer system may further include a display un
it 319, such as a liquid crystal display (LCD), an organic light emitti
ng diode (OLED), a flat panel display, a solid‐state display, a cathode ray tube (CRT), a p
rojector, a printer or other now known or later developed display device for outputting dete
rmined information. The display 319 may act as an interface for the user to see t
he functioning of the processor 312, or specifically as an interface with the instructions st
ored in the memory 314 or elsewhere in the control unit 210. [00114] Additionally, the computer system may include an inpu
t device 317 configured to allow a user to interact with any of
the components of system. The input device 317 may be a number pad, a keyboard, or a
cursor control device, such as a mouse, or a joystick, touch screen display, remote c
ontrol, or any other device operative to interact with the control unit 210. [00115] The present disclosure contemplates a computer‐readab
le medium that includes instructions or receives and executes instruc
tions responsive to a signal, so that a device connected to a network can communicate voic
e, video, audio, images, or any other data over the network. Further, the instruction
s may be transmitted or received over the network via a communication interface 318.
The communication interface 318 may be a part of the processor 312 or may be a s
eparate component. The communication interface 218 may be a physical connect
ion in hardware. The communication interface 318 is configured to connect
with a network, external media, the display unit 319, or any other components in th
e system, or combinations thereof. The connection with the network may be a physical c
onnection, such as a wired Ethernet connection or may be established wirelessly.
Likewise, the additional connections with other components of the system may
be physical connections or may be established wirelessly. [00116] The illustrations of the embodiments described herein
are intended to provide a general understanding of the structure of
the various embodiments. The illustrations are not intended to serve as a complet
e description of all of the elements and features of apparatus and systems that utilize t
he structures or methods described herein. Many other embodiments may be apparent to th
ose of skill in the art upon reviewing the disclosure. Other embodiments may be ut
ilized and derived from the disclosure, such that structural and logical substitut
ions and changes may be made without departing from the scope of the disclosure.
Additionally, the illustrations are merely representational and may not be drawn to scal
e. Certain proportions within the illustrations may be exaggerated, while other proporti
ons may be minimized. Accordingly, the disclosure and the figures are to b
e regarded as illustrative rather than restrictive. [00117] While this specification contains many specifics, thes
e should not be construed as limitations on the scope of the inventi
on or of what may be claimed, but rather as descriptions of features specific to partic
ular embodiments of the invention. Certain features that are described in this specifica
tion in the context of separate embodiments can also be implemented in combination in
a single embodiment. Conversely, various features that are described in th
e context of a single embodiment can also be implemented in multiple embodiments separ
ately or in any suitable sub‐ combination. Moreover, although features may be descri
bed as acting in certain combinations and even initially claimed as such, one
or more features from a claimed combination can in some cases be excised from the c
ombination, and the claimed combination may be directed to a sub‐combination or
variation of a sub‐combination. [00118] Similarly, while operations are depicted in the drawi
ngs and described herein in a particular order, this should not be un
derstood as requiring that such operations be performed in the particular order shown
or in sequential order, or that all illustrated operations be performed, to achieve desira
ble results. In certain circumstances, multitasking and parallel processing may
be advantageous. Moreover, the separation of various system components in the d
escribed embodiments should not be understood as requiring such separation in all em
bodiments, and it should be understood that the described program components and
systems can generally be integrated together in a single software product or
packaged into multiple software products.
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