Technical Field

[001] The invention concerns an aerial vehicle which will generate lift thrust directly from motors which will usually be provided by one or more vertical axis rotors (eg., propellers or ducted fans), but may include other moving wing thrusters such as an ornithopter or non-wing thrusters such as jets or rockets. The aerial vehicle may be either unpiloted (UAV) or remotely piloted (RAV) and for the sake of brevity will be referred to herein as an aerial vehicle. The aerial vehicle of the invention is intended primarily as a toy, but may have a range of other applications including search and inspection, particularly in confined environments.

Prior Art

[002] Moving wing aerial drones consist of a chassis supporting one or more motors, an onboard controller and a power supply which may be referred to collectively in this specification as the lift assembly. The motors will be configurable to generate lift directly by exhausting downwardly. Most commonly a motor is arranged to generate lift by spinning a propeller about a substantially vertical axis. In some aerial drones a single vertical axis propeller may be employed and the rotary axis tilted from the vertical to generate thrust in a horizontal direction. To counter the effect of propeller torque a horizontal axis propeller may be used. However, it is now common for drones to employ multiple counter rotating rotors, for example two or four to counter the effect of torque. Rotors may be mounted on concentric axis or on multiple spaced axes. Any or all of: the sense of rotation (clockwise or counter clockwise), relative speed and attitude of each propeller may be controlled to control the aerial vehicle pitch, roll, yaw, airspeed and altitude.

[003] Controllers are commonly responsive to wireless control signals generated from a remote, manually operable control console. To minimise the skill required of an operator an onboard controller runs a control algorithm to manage the individual motor rotation speed and attitude in response to gross control instructions defining direction, airspeed, altitude (up or down) and horizontal direction (forward, back, left or right) and feedback from an onboard sensor array. Although toy drones tend to be light weight and rarely carry more payload than a small camera, deliberate or accidental misuse can result in collision causing damage to the aerial vehicle and injury to ambient structures or persons. The larger an aerial vehicle gets, the greater is the potential for injury. Operation of the aerial vehicle in confined spaces or where unexpected changes of air current occur can provoke collisions with nearby fixed structures. Such collisions may damage the aerial vehicle or the structure and/or cause the aerial vehicle to fall or recoil in an uncontrolled hazardous manner.

[004] In an effort to alleviate the risk of injury designers have begun enclosing drones in a drum shaped fender cage as disclosed in perspective view in figure 1.1 and in section in figure 1.2. Further details of this type of aerial vehicle are disclosed in US2014/0131507 A1 . The aerial vehicle in figures 1.1 and 1.2 comprises a chassis with a ring 1 , a pair of spokes 2 each extending radially in towards the centre of the ring 1 , and a pair of spokes 3 extending radially out from the ring 1 . The inwardly extending spokes support a housing 4. The housing 4 may incorporate a controller, power cells and wireless communication system (not shown). The ring also supports four equiangularly spaced rotors 5, each comprising a vertical axis propeller blade 6 and, a motor and housing 7. The outer spokes 3 support a barrel shaped cage 8 formed from a number of elongate rigid members connected at nodes. The spokes all lie on a longitudinal axis (L). Each of spokes 3 engages the elongate cylindrical cage 8 at a cage hub 9 which accommodates a bearing 10 to enable the cage to rotate around the longitudinal axis corresponding to the long axis of the outer spokes 3. The aerial vehicle also has a vertical axis (V) and a lateral axis (H). The cage consists of a framework so that the blades 6 cannot collide with a substantial external object. The cage 8 comprises endless ring members centered on the hubs to which they are connected via arcuate spoke members. The endless ring members mounted to longitudinally opposite hubs are connected via longitudinal members. The aerial vehicle can be flown to roll up a surface such as a wall or along a ceiling or floor so long as the long axis (L) is parallel to the surface and movement is perpendicular to the long axis. However, if the aerial vehicle collides with an object while moving in any direction not sufficiently perpendicular to the long axis it may be caused to tumble in an uncontrolled manner. Figures 5 and 6 of US2014/0131507 A1 disclose an aerial vehicle similar to that described above but having a spherical cage. If the aerial vehicle is induced to tumble the aerial vehicle can only recover by the control driving the motors to rectify the tumbling motion. Because of the inertia of the cage this puts increased demands on the controller and rotors. Flyability SA have sought to alleviate the problem mentioned in the preceding paragraph by means of the "Gimball™" aerial vehicle which can be found at

http ://www.flyabi I ity. com/prod uct/. The prior art Flyability aerial vehicle is reproduced at figures 2.1 and 2.2 which show a gimbal between the aerial vehicle chassis/motor/controller (CMC) assembly and a generally spherical cage such that the cage can rotate in any direction relative to the CMC assembly enabling the CMC assembly to remain substantially vertical. In figures 2.1 and 2.2 integers common to the prior art of figures 1 .1 and 1.2 are similarly numbered. The prior art of figures 2 differs from that of figures 1 in that the single propeller 5' provides counter rotating coaxial blades 6' and 6" and is integrated with the CMC. The inner spokes 2 rigidly connect the housing to the ring 1. Unlike the prior art of figure 1 the ring 1 is freely rotatably connected to a gimbal ring 1 1 by rotary bearings 12 disposed on the longitudinal axis (L). The gimbal ring 1 1 is freely rotatably connected to a cage 8' via rotary bearings 13 which act on any axis perpendicular to the longitudinal axis, as shown this is the vertical axis V-V. The cage 8' is formed from a mesh of substantially rigid straight struts connected to each other at nodes, where the nodes are all sited on a notional sphere. The polyhedral shape thus created can therefore roll readily in any rotary direction around the housing 4 and rotors 6 and does not restrict airflow across the rotors. This "Gimball" aerial vehicle thus alleviates the technical problems explained with reference to figure 1 in that the cage can move in any direction against a surface without applying significant torque to the housing and lift assembly 4, 6 and minimises the risk of destabilising flight. However, the "Gimball" requires a cage which is complex to fabricate, requires the extra gimbal ring 1 1 and two additional rotary bearings 13. In addition to extra steps in fabrication this makes the "Gimball" heavy, reducing its payload and/or range and/or requiring fabrication from high strength to weight ratio and therefore expensive materials which are often difficult and therefor expensive to work with.

[007] It is an object of the present invention to provide an aerial vehicle with collision

stability characteristics similar to those of the "Gimball" having a structure which may be relatively less complex to assemble, has fewer components and may be fabricated with an improved strength to weight ration.

Statement of Invention

[008] A moving wing aerial vehicle with a fender cage:

a lift assembly,

an endless annular track,

a rotary bearing operable between the lift assembly and a fender cage to provide for free rotation around a first axis;

the endless annular track operable between the fender cage and the lift assembly to allow the fender cage to rotate around a second axis perpendicular to the first axis whereby the fender cage can rotate about two mutually perpendicular axes extending through the lift assembly.

[009] In a second embodiment of the aerial vehicle the endless annular track is provided by a ring concentric with the lift assembly. The annular track may extend around the whole lift assembly or; parts of the lift assembly, such as the propeller blades, may overlap the track. A rotor may engage with the track to rotate freely around the track. A spoke extends radially from the rotor to engage with a bearing mounted in a hub of the fender cage. This arrangement helps to reduce the weight of the annular track and the overall weight of the aerial vehicle without adversely affecting the stiffness or strength of the assembled aerial vehicle.

[010] In an alternative variant of the second embodiment the rotary bearing may be

mounted in the rotor so that the spoke and fender cage can rotate on an axis perpendicular to the rotary axis of the rotor.

[on] The cage is preferably formed from arcuate members which may all have a

common radius of curvature corresponding to the radius of a notional sphere such that when assembled into the cage the cage members lie in, or on, the surface of the sphere.

[012] The lift assembly may include each propeller, power supply, onboard controller wireless communication system and a supporting chassis. The lift assembly may also provide a platform for any payload such as a camera.

[013] In the second embodiment the annular track is immovably oriented with respect to the axis of the or each propeller. For example the annular track may be oriented to have a central axis perpendicular to the propeller axis.

[014] The annular track may include features to facilitate movement of the rotor such as low friction bearing surface, or the rotor may include such features. For example the track may include rolling elements, or the rotor may incorporate rolling elements. The rotor may extend circumferentially around the annular track by a distance greater than the width of the track. Preferably the aspect ratio of the rotor width to circumferential extent will be 1 :6 or more. [015] Accordingly the present invention provides a moving wing aerial vehicle with a fender cage: a lift assembly, an endless annular track, a rotary bearing engaged with the endless annular track to slide around the track and support the fender cage whereby the fender cage can rotate about two mutually perpendicular axes extending through the lift assembly.

[016] The track may form an integral part of the cage. In this case spokes may extend from the lift assembly to engage with the rotary bearing. The rotary bearing may engage directly with a slider received into a groove in the track.

[017] Resilient means such as a compression coil spring may be arranged to urge the bearing into engagement with the track. The bearing may comprise one or more rolling elements.

[018] The track is provided by a cage member in the form of an endless ring. The cage member may provide the track by means of a channel. The channel may be provided by a member having a "U" shaped cross section.

Brief Description of Figures

low] Embodiments of a moving wing aerial vehicle with a fender cage rotatable about two perpendicular axes constructed in accordance with the present invention, will now be described, by way of example only, with reference to the accompanying illustrative figures; in which,

Figure 3.1 is an isometric SE view of a first embodiment;

Figure 3.1 .1 . is an enlarged perspective fragmental detail view of the bearing from figure 3.1 ;

Figure 3.2 is a front sectional elevation of the first embodiment; Figure 3.2.1 is a sectional elevation in the view line 3.2.1 in figure 3.2; and

Figure 3.2.2 is a sectional elevation on the view line 3.2.2 in figure 3.2;

Figure 4.1 is an isometric SE view of a second embodiment;

Figure 4.2 is a sectional front elevation of the second embodiment without the rotors;

Figure 4.3 is a fragmentary detail sectional view from figure 4.2; and

Figure 4.4 is an exploded SE isometric of the aerial vehicle with the rotors and fender cage omitted.

Figure 5.1 is a plan view of a third embodiment of the moving wing aerial vehicle with a fender cage rotatable about two perpendicular axes;

Figure 5.2 is a front elevation of the third embodiment;

Figure 5.3 is a SE isometric view of the third embodiment; and

Figure 5.4 is a view of a minor ring part from the third embodiment;

Figure 5.5 is a SE isometric view of an inner part of a hub;

Figure 5.6 is a SW isometric view of an outer part of the hub.

Detailed Description of Figures

First embodiment

The aerial vehicle illustrated by the figures has a lift assembly comprising a chassis, a housing 4 and four rotors 5. The chassis comprises a substantially rigid ring 1 , a pair of inner spokes 2 which extend towards the centre of the ring to support the housing 4, and a pair of outer spokes 3 which extend radially out from the ring 1. The housing 4 is conventional and houses a power supply, onboard controller and wireless communication system connected via communication lines to each propeller 5. The four rotors 5 are mounted equiangularly spaced around the ring 1 with the axis of each blade 6 parallel to the vertical axis V-V of the aerial vehicle.

[021] The cage 8 is formed from: a track ring 14, a pair of hubs 15; three major rings 16; and two minor rings 17. The axially opposed hub structures 15 are each attached to the track ring 14 and disposed in axially opposing positions. The track ring 16 may be formed from plastics by moulding, with the hubs 15 being an integrally moulded part of the track ring 14. To minimise the weight of the track ring 14 it may be formed with an outer web 18 supporting angularly spaced flanges 19. Each angularly spaced flange 19 extends radially inwardly from an edge of the outer web 18 to support an endless retaining rail 20 forming a guide channel providing the track to constrain the bearing 10. The web 18 may also include vacant regions to further minimise weight.

[022] Each of the three major rings 16 is attached to each of the hubs 15 at intervals to be angularly spaced from the track member 18 and each other.

[023] Each of the major rings 16 is fed through a complementary sectioned hole formed in each minor ring 17 to secure the minor rings 17 to the major rings 16. Each of the major rings 16 is secured into corresponding holes formed in each hub 15. The track ring 14 is secured to each minor ring 17 by means of features moulded onto the track ring 14 which engage with the section of minor ring 17.

[024] Each outer spoke 3 comprises a tubular member 21 telescopically received into a corresponding tubular inner spoke 2. Each outer spoke is sleeved onto a connecting spring rod 22 which extends diametrically across the centre of the ring 1 and supports a coil spring 23 so that the coil spring bears against the outer spokes 3 and urges them radially outwards. The outer ends of each outer spoke support a cup shaped cylindrical bearing housing 24. A rolling element or ball bearing 25 is retained in the bearing housing 24. Thus when assembled the spring 23 presses the bearing housing 24 and ball bearing 25 into the track formed by the web 18 and rails 20.

[025] In use the cage 8 can freely rotate in any direction around the lift assembly without transmitting significant torque to the lift assembly and disrupting the overall stability of aerial vehicle.

Second embodiment

[026] Referring to figures 4.1 -4.3 the aerial vehicle comprises a lift assembly having a housing 104 housing and four rotors 105. The housing houses a power supply (usually electrochemical cells), an onboard controller and wireless communication system connected via communication lines to each of the four rotors 105. Each propeller 105 is supported on one of four cantilevers 106 extending from the housing 104. Each cantilever 106 extends radially from a vertical axis,

equiangularly spaced and lying in a common, horizontal plane. Each rotary axis of each propeller is situated at a similar propeller radius from a central vertical axis "V" of the aerial vehicle.

[027] The housing 104 supports a diametrically extending spoke 107 extending through a centre of the aerial vehicle. The spoke 107 supports an integrally formed annular track 108. The annular track 108 is concentric with the aerial vehicle centre through which the vertical axis and a lateral axis LA-LA pass. Thus the annular track moves (rotates, pitches and yaws) with the housing 104. [028] The annular track 108 consists of a track ring 109 into which are formed four circumferentially extending equiangularly spaced slots 1 10. The side walls of each slot are perforated by a plurality of spaced holes 1 1 1 extending in the

circumferential direction of the slot and spaced to receive an axle of a rolling element 1 12. The annular track is captured in a track rotor 1 13. Track rotor 1 13 comprises a first ring 1 14 and a second ring 1 15. The first and second rings have inner and outer radii such that they span the annular track 108. A plurality of axially extending tongues 1 16 extend from the outer periphery of the first ring 1 14. Each tongue 1 16 is circumferentially extending and circumferentially spaced from the other tongues. Each tongue terminates in a barb formation 1 17. The tongue 1 16 extends axially to an extent sufficient that when the first ring is brought up to one side of the annular track 108, and the second ring is brought up to the opposite side of the annular track 108, each tongue engages in a corresponding slot 1 17A formed in the periphery of the second ring 1 15 and is trapped by the barb 17. Thus the annular track 108 is caged by the track rotor 1 13. The tongues 1 16 have internal surfaces which bear on the rolling elements 1 12 and the span of the tongues is such that the track rotor 1 13 can rotate freely around the annular track 108.

[029] Two of the tongues 1 16A provide mounting points for each of two outer spokes

1 19a which extend radially away from the aerial vehicle axis and each terminate in a rotary bearing 1 19. Each rotary bearing 1 19 is adapted to be received into a bearing housing 120 formed in the cage hub 15 so that each outer spoke 1 19a can rotate around its long axis. [030] The fender cage has four major rings 121 which radiate from each hub 120 and are joined to each of four minor rings 121 at a node. The minor rings 121 are spaced along the lateral axis "LA" extending between the hubs 120.

[031] The assembly of the aerial vehicle thus comprises assembling the annular track 108 with the track rotor 1 13. Installing the control components and battery into the housing 104 and attaching the housing to the inner spoke 107. Attaching the rotors 105 to the cantilevers 106. Sleeving each hub 15 onto the ends of the outer spokes 1 19a and retaining the outer spokes 1 19a in each hub 15 by means of the bearings 1 19 engaged into the bearing housings 120. The four major rings 121 are formed by sleeving the resilient elongate members through a node connector having a sleeve 123 and a saddle 124 to engage with each hub 15. Then the minor rings 122 are snapped into the node saddles124 to form a resilient fender cage.

[032] The resulting aerial vehicle of the second embodiment can be made relatively

lighter than the first embodiment. Assembly of the cage is relatively quick and therefore inexpensive. The notional surface of the aerial vehicle cage is a sphere made up of curvilinear squares defined by the arc of each ring between the nodes connecting the minor and major rings. This configuration together with the use of a node saddle to join the major and minor rings allows the cage to flex resiliently on impact with any other surface thus the degree of injury or damage caused on impact is minimised.

Third embodiment

[033] The third embodiment of the invention is generally similar to the second

embodiment with the major rings 121 and minor rings 122 of the cage lying in a notional spheroidal surface so that when the UAV engages a nominally flat surface such as the ground or a ceiling it can roll in any direction parallel to the surface. In the first and second embodiments the hub 15 also lies in or immediately under the nominal spheroidal surface such that when rolling along a nominally flat surface the hub can engage the flat surface. The cage rings 121 and 122 are inevitably resiliently flexible and, therefore deform as the UAV rolls along the surface. The hub is supported by the spoke 1 19a and therefore deforms in response to load differently to the cage rings 121 , 122. This effect has been found to cause the UAV to hop in a way which makes it difficult to control and is therefore undesirable. Stiffening the cage rings to moderate the deformation and therefore the hopping effect is undesirable as this adds to the weight of the UAV. In the third embodiment the hub 15 is located at a radius less than the nominal radius of the notional spherical surface. This is achieved by forming each major cage ring 121 from two major ring parts, 121 .1. Each minor ring part has a first arcuate part 121 .2 which at rest has a uniform radius of curvature (R1 ). The first arcuate part provides the rolling or contact surface in the cage and terminates at each end with a second arcuate part 121 .3 having a much smaller radius of curvature (R2). In the embodiment the ratio of radius of curvature (R1/R2) is 18, however this may vary somewhat according to the overall size (radius) of the UAV cage and the materials used to form the rings. The second arcuate part progresses into a straight part 121.4 which terminates in a hooked part 121.5. The hooked part 121 .5 locates in a hook receiving socket 121 .6 formed into the hub 120, the straight part locates into a groove 121.7 formed into the hub 120 to maintain the angular spacing of the minor ring parts 121 .1 around the axis "L". The second arcuate part 121 .3, the straight part 121 .4 and the hooked part 121 .5 provide a hub engaging portion. As can best be seen in figure 5.5 and 5.6, the grooves and hook receiving features are formed into a hub 120 assembled from an inner hub part 120.1 and an outer hub part 120.2. As a result the deformation of the cage caused by rolling against a surface does not bring the hub 120 into direct contact with the surface and the unwanted hopping phenomenon is mitigated.

[035] To facilitate assembly of the third embodiment and to provide for resilient

deformation of the fender cage the major rings 121 and minor rings 122 are connected via node connectors comprising a first tubular sleeve 123 and a second perpendicular sleeve 125 tangential to the first sleeve 123. The first sleeve 123 is divided by a slot 126 extending parallel to the bore 127 of the first sleeve. This allows the bore 127 to resiliently deform in order to be snapped over the major ring 121 when assembling the fender cage. The bore 127 may be sized to a close sliding fit over the major ring. The bore 128 of the second sleeve may be a loose sliding fit to facilitate assembly, deformation of the fender cage on impact and subsequent recovery to the spherical shape.

[036] It is desirable to make the size of the hub as small as possible. A large hub will be heavy; which is obviously undesirable in a UAV. Moreover, in a UAV according to the third embodiment the large hub distorts the sphericality of the fender cage. The use of relatively large diameter hubs also tends to adversely affect the orientation of the lateral rotary axis LA. The lateral axis being the axis passing through the centre of each hub. When the fender cage impacts a surface it is desirable that it does so along the longitudinal axis and with the lateral axis perpendicular to the direction of motion and the surface. It has been found that the use of a relatively large hub diameter encourages the lateral axis to move towards a vertical orientation during flight. The use of a relatively smaller hub reduces this tendency. In a variant of the unmanned aerial vehicle the friction between the track ring 108 and the track rotor 1 13 may be varied by the introduction of a spring or other mechanism to bias the orientation of the lateral axis to align with the spoke 107.