Mechanism for providing compliance adjustment for a robot appendage

Abstract

A mechanism for providing compliance adjustment for a robot appendage configured to engage a surface, the mechanism including: a rigid member; and a flexible member connected to the rigid member, the flexible member being moveable between: a first stable position in which the flexible member is deformable relative to the rigid member to thereby provide a first degree of compliance; and a second stable position in which the flexible member is deformed to constrain movement of the flexible member to thereby provide a second degree of compliance which is lower than the first degree of compliance, wherein the mechanism is attached to the robot appendage to provide a first or second degree of compliance when the robot appendance engages the surface.

Description

MECHANISM FOR PROVIDING COMPLIANCE ADJUSTMENT FOR A ROBOT APPENDAGEBackground of the Invention

[0001] The present disclosure is directed to a mechanism for providing compliance adjustment for a robot appendage.Description of the Prior Art

[0002] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgement or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[0003] In robotics, variable stiffness is important to address the trade-off between the need for compliance for safe interaction with the environment and the ability to enforce stability when required. Whilst some variable-stiffness systems utilise pneumatics and hydraulics, these are often prone to leaks and punctures. Further, abrasive environments can quickly wear out fluid or gaseous filled membranes, leading to failure.Summary of the Present Invention

[0004] One or more embodiments of the present invention include a mechanism for providing compliance adjustment for a robot appendage configured to engage a surface, the mechanism including: a rigid member; and a flexible member connected to the rigid member, the flexible member being moveable between: a first stable position in which the flexible member is deformable relative to the rigid member to thereby provide a first degree of compliance; and a second stable position in which the flexible member is deformed to constrain movement of the flexible member to thereby provide a second degree of compliance which is lower than the first degree of compliance, wherein the mechanism is attached to the robot appendage to provide a first or second degree of compliance when the robot appendance engages the surface.

[0005] In some embodiments, in the second stable position the flexible member engages the rigid member.

[0006] In some embodiments at least one of: the mechanism is attached to the robot appendage so that the mechanism is provided between the robot appendage and the surface; the robot appendage is attached to the rigid member; the rigid member is part of the robot appendage; the robot appendage is attached to the flexible member; or the rigid member is a first rigid member and the robot appendage is attached to the flexible member via a second rigid member.

[0007] In some embodiments the rigid member is a first rigid member and a second rigid member is attached to the flexible member.

[0008] In some embodiments, the first and second rigid members engage with each other such that their relative movement is substantially restricted in the second stable position.

[0009] In some embodiments, the first rigid member includes a valley configured to receive a projection of the second rigid member, wherein when the projection is received within the valley, the projection engages with the valley to restrict relative movement of the rigid members.

[0010] In some embodiments, the second rigid member includes a plate defining a first face that opposes the first rigid member.

[0011] In some embodiments, when the flexible member is in the second stable position, at least a portion of the first face contacts at least a portion of the first rigid member, thereby restricting the relative movement of the rigid members.

[0012] In some embodiments, the flexible member includes first and second mountings proximate opposing ends of the flexible member, wherein the first and second mountings are configured to couple the flexible member to the rigid member.

[0013] In some embodiments, the flexible member includes: a central spine; and a first arm extending from the spine supporting the first mounting and a second arm extending from the spine supporting the second mounting.

[0014] In some embodiments, a second rigid member is connected to the central spine.

[0015] In some embodiments, the second rigid member is pivotably mounted to the spine to allow an orientation of the second rigid member to adapt when engaging the surface in at least the first stable position.

[0016] In some embodiments, the second rigid member is configured to engage the surface and wherein the second rigid member is pivotally mounted to the flexible member so that the second member aligns with the surface during engagement.

[0017] In some embodiments, in the first stable position, the flexible member has an inverted V-shape; and in the second stable position, the flexible member is substantially V-shaped.

[0018] In some embodiments, the rigid member includes first and second rigid member mountings proximate opposing ends of the rigid member, wherein the first and second rigid member mountings are configured to couple the flexible member to the rigid member.

[0019] In some embodiments, the rigid member includes a base and rigid member arms extending at an angle from the base.

[0020] In some embodiments, the flexible member is caused to be moved between the first and second stable positions by applying a force to the flexible member.

[0021] In some embodiments, the force required to move the flexible member between the first and second stable positions depends on one or more of a material of the flexible member; dimensions of the flexible member; a thickness of at least part of the flexible member; dimensions of first and second arms of the flexible member; and a shape of the flexible member; an angle of a V-shape of the flexible member.

[0022] In some embodiments, an actuator is provided to return the flexible member to the first stable position.

[0023] In some embodiments, the first rigid member is configured to engage with the surface.

[0024] In some embodiments, the second rigid member is configured to attach to the robot appendage.

[0025] In some embodiments, the robot appendage defines the second rigid member.

[0026] In some embodiments, the second rigid member is configured to engage with the surface.

[0027] In some embodiments, the first rigid member is configured to attach to the robot appendage.

[0028] In some embodiments, the robot appendage defines the first rigid member.

[0029] In some embodiments, the flexible member is formed from a material selected from: plastic; polymer; or metal.

[0030] In some embodiments, the mechanism includes a sensor configured to detect operation of the mechanism.

[0031] In some embodiments, the sensor is configured to detect if the flexible member is in the first stable position or second stable position.

[0032] In some embodiments, the mechanism includes a surface engaging member configured to engage a surface.

[0033] One or more embodiments of the present invention include a device including a plurality of the mechanisms according to the present disclosure, wherein each of the plurality of the mechanisms are attached to at least one other mechanism of the plurality of mechanisms.

[0034] It will be appreciated that the broad forms of the invention and their respective features can be used in conjunction and / or independently, and reference to separate broad forms is not intended to be limiting. Furthermore, it will be appreciated that features of the method can be performed using the system or apparatus and that features of the system or apparatus can be implemented using the method.Brief Description of the Drawings

[0035] Various examples and embodiments of the present invention will now be described with reference to the accompanying drawings, in which: -

[0036] Figure 1 A is an isometric view of a mechanism for providing compliance adjustment in a first stable position;

[0037] Figure IB is a side view of the mechanism as shown in Figure 1 A;

[0038] Figure 1C is a top down view of a mechanism for providing compliance adjustment;

[0039] Figure ID is a side view of the mechanism of Figure 1A in a second stable position;

[0040] Figure 2A is an isometric view of a mechanism for providing compliance adjustment in a first stable position;

[0041] Figure 2B is an isometric view of a mechanism for providing compliance adjustment in a second stable position in a second position;

[0042] Figure 3 is an isometric view of a plurality of the locking mechanism of Figure 1A arranged into a grabbing device;

[0043] Figure 4A is a schematic perspective view of an example of a mechanism for providing compliance adjustment in the second stable position;

[0044] Figure 4B is a schematic side view of the mechanism of Figure 4A;

[0045] Figure 4C is a schematic perspective view of the mechanism of Figure 4A in the first stable position after actuation of a return mechanism;

[0046] Figure 4D is a schematic side view of the mechanism of Figure 4A in the first stable position after actuation of a return mechanism;

[0047] Figure 4E is a schematic perspective view of the mechanism of Figure 4A;

[0048] Figure 4F is a schematic perspective view of the mechanism of Figure 4A modified to include a sensor;

[0049] Figures 5 A to 5E are a sequence of schematic side views of an example of a compliance adjustment mechanism undergoing deformation;

[0050] Figures 6A to 6E are a sequence of schematic side views of simulated von Mises stresses on the compliance adjustment mechanism of Figures 5 A to 5E during deformation;

[0051] Figure 7A is a graph of an example of reaction force versus displacement for the compliance adjustment mechanism of Figures 5 A to 5E;

[0052] Figure 7B is a graph of an example of strain energy versus displacement for the compliance adjustment mechanism of Figures 5 A to 5E;

[0053] Figure 8A is a schematic diagram of an example of grabber incorporating compliance adjustment mechanisms;

[0054] Figure 8B is a schematic diagram of the grabber of Figure 8 A in use;

[0055] Figure 8C is a schematic diagram of a side view of the compliance adjustment mechanisms of Figure 8 A in a first stable position;

[0056] Figure 8D is a schematic diagram of a side view of the compliance adjustment mechanisms of Figure 8 A in a second stable position so that the hooks engage a surface.Detailed Description of the Preferred Embodiments

[0057] The present disclosure is directed to a mechanism for providing compliance adjustment for a robot appendage.

[0058] An example mechanism 100 for providing compliance adjustment for a robot appendage (not shown) configured to engage a surface (not shown) will now be described with reference to Figures 1 A to ID.

[0059] In this example, the mechanism 100 includes a rigid member 110 and a flexible member 150 connected to the rigid member 110. The nature of the rigid and flexible members may vary depending on the preferred implementation, and specific examples will be described in more detail below.

[0060] The flexible member 150 is moveable between a first stable position in which the flexible member 150 is deformable relative to the rigid member 110 to thereby provide a first degree of compliance and a second stable position shown in Figure ID in which the flexible member 150 is deformed to constrain movement of the flexible member 150 to thereby provide a second degree of compliance which is lower than the first degree of compliance. In one example, constraint of movement when in the second position can be achieved by having the flexible member 150 deform so that it engages the rigid member 110, although this is not essential, and constraint of the flexible member may arise due to the shape and configuration of the deformed flexible member. For example, deformation of the flexible member may induce stress within the flexible member to constrain further movement beyond the second stable position, and / or movement might be constrained by the shape of the flexible member in the second stable position.

[0061] In use, the mechanism is attached to the robot appendage to provide a first or second degree of compliance when the robot appendance engages the surface. This can be achieved by attaching the robot appendage to either the rigid or flexible member, and / or by incorporating the mechanism into the robot appendage, for example by incorporating this into an arm or leg, or an articulated joint such as a wrist or ankle.

[0062] Irrespective of how this is achieved, the mechanism acts to provide a binary stiffness change through the exploitation of the bi-stability of a flexible member. Thus, in the first position, a higher degree of compliance can be provided, which in turn can protect the robot appendage or engaged surface during the engagement process. This is particularly important when engagement can result in high forces, such as when a robot is undergoing locomotion, such as running or the like. Conversely, in the second position, reduced compliance is provided, which in turn allows the engagement to occur with a higher degree of accuracy. This in turn can be useful when highly accurate positional engagement is required, such as when interacting with objects, such as buttons or switches.

[0063] These mechanisms can also be arranged linearly or in an array, allowing layout customisability for various applications. The mechanisms can be used to provide compliance adjustment for a robot appendage configured to engage a surface.

[0064] A number of further features will now be described.

[0065] In one example, the mechanism is attached to the robot appendage so that the mechanism is provided between the robot appendage and the surface. This ensures compliance control is provided whenever the robot appendage engages a surface. This can be achieved in a variety of manners, such as attaching the robot appendage to the rigid member, having the rigid member as part of the robot appendage, attaching the robot appendage to the flexible member; or attaching the robot appendage to the flexible member via a second rigid member. The particular mechanism used will vary depending on the nature of the robot appendage, and the circumstances in which this is to be used.

[0066] In one example, the rigid member is a first rigid member and a second rigid member is attached to the flexible member. The use of a second rigid member in this fashion can provide certain benefits, for example ensuring better engagement with the surface, and / or offering greater stability in the first or second positions.

[0067] In one example, the first and second rigid members can engage with each other such that their relative movement is substantially restricted in the second stable position, which can in turn help limit relative movement of the first and second rigid members, and allow for engagement with a higher degree of positional accuracy.

[0068] In one example, the first rigid member includes a valley configured to receive a projection of the second rigid member, wherein when the projection is received within the valley, the projection engages with the valley to restrict relative movement of the rigid members. This helps further limit relative movement of the first and second members, and particularly ensures the members hold position when subject to high engagement forces.

[0069] In one example, the second rigid member includes a plate defining a first face that opposes the first rigid member. In this arrangement, when the flexible member is in the second stable position, at least a portion of the first face contacts at least a portion of the first rigid member, thereby restricting the relative movement of the rigid members.

[0070] In one example, the flexible member includes first and second mountings proximate opposing ends of the flexible member, wherein the first and second mountings are configuredto couple the flexible member to the rigid member. This provides a straightforward mechanism for interconnecting the flexible and rigid members, whilst allowing the flexible member to switch between the first and second positions.

[0071] Whilst the configuration of the flexible member may vary depending on the implementation, in one example, the flexible member includes a central spine, a first arm extending from the spine supporting the first mounting and a second arm extending from the spine supporting the second mounting. In this situation, movement of the arms can then provide for compliance, as well as allowing the flexible member to switch between the first and second positions, while the central spine can be used to allow the second rigid member to be connected thereto.

[0072] In one example, the second rigid member is pivotably mounted to the spine to allow an orientation of the second rigid member to adapt when engaging the surface in at least the first stable position. In this arrangement, this allows the second rigid member to engage the surface and wherein the second rigid member is pivotally mounted to the flexible member so that the second member aligns with the surface during engagement. This can be used, for example, to allow the second rigid member to lie flat on the surface, even if the mechanism itself is angled relative to the surface, which can help improve surface engagement, for example maximising grip or the like.

[0073] In one example, in the first stable position, the flexible member has an inverted V-shape, whereas in the second stable position, the flexible member is substantially V-shaped. In this instance, the V-shape of the flexible member retains the member in the first or second position, until sufficient force is applied to the member, to switch the member into the other position.

[0074] In one example, the rigid member includes first and second rigid member mountings proximate opposing ends of the rigid member, wherein the first and second rigid member mountings are configured to couple the flexible member to the rigid member. The mountings can be of any form, but in one example include openings for receiving a fastener, such as a locking pin or bolt, allowing for relative movement of the flexible and rigid members.

[0075] In one example, the rigid member includes a base and rigid member arms extending at an angle from the base, allowing the arms to support the rigid member mountings.

[0076] In one example, the flexible member is caused to be moved between the first and second stable positions by applying a force to the flexible member. This can be used to enable the flexible member to be controllably switched between states. This could be achieved using an actuator, but could also be achieved for example, by having the robot appendage apply a force to the mechanism to cause the flexible member to move from the first to the second position.

[0077] The force required to move the flexible member between the first and second stable positions depends on one or more of a material of the flexible member, dimensions of the flexible member, a thickness of at least part of the flexible member, dimensions of first and second arms of the flexible member, a shape of the flexible member or an angle of a V-shape of the flexible member. It will be appreciated from this, that this enables the mechanisms to be easily configured for a particular usage, by suitably configuring the material and dimensions of the flexible member.

[0078] In one example, an actuator, such as a linear actuator, or the like, can be provided to return the flexible member to the first stable position. This allows the mechanism to be repeatedly switched between states as needed.

[0079] The mechanism can be used in a variety of ways, depending on the preferred implementation. For example, the first rigid member is configured to engage with the surface, in which case the second rigid member can be configured to attach to the robot appendage, or the robot appendage acts as the second rigid member. Alternatively, the second rigid member is configured to engage with the surface, in which case the first rigid member can be configured to attach to the robot appendage, or could define the first rigid member. This configurability allows the mechanism to be deployed in a wide range of different scenarios.

[0080] The flexible member is typically formed from a material selected from any suitable plastic, polymer, metal or any other suitable material.

[0081] A specific example arrangement will now be described.

[0082] According to some embodiments, the mechanism 100 includes a rigid member 110.

[0083] The rigid member 110 may include or define face 115, and the face 115 may include and / or define attachment valley 120. According to some embodiments, the mechanism 100 may be attached to the robot appendage via face 115 and / or attachment valley 120 so that the mechanism 100 is provided between the robot appendage and the surface. According to some embodiments, the rigid member 110 may include or define mating structure 135 configured to enable the rigid member 110 to be affixed or otherwise attached to the robot appendage. For example, and as shown in Figure 1 A, the mating structure 135 may be configured to receive a fastener (such as a bolt, nut, screw, nail or other similar fastener) therethrough, which may then engage with the robot appendage to allow the rigid member 110 to be attached thereto. According to some embodiments, the robot appendage may be configured to attach to the rigid member 110. According to some embodiments, the rigid member 110 may form part of, or be integrated with the robot appendage.

[0084] According to some embodiments, the mechanism 100 includes a flexible member 150 connected to the rigid member 110. The flexible member 150 may include or define a central spine 155, first arm 160 and second arm 162. In some embodiments, the first arm 160 attaches a first mounting 165 to the central spine 155. In some embodiments, the second arm 162 attaches a second mounting 167 to the central spine 155.

[0085] According to some embodiments, the flexible member 150 is attached to the rigid member 110 by the first mounting 165 and the second mounting 167. As shown in Figures 1 A to 1C, the first mounting 162 engages with a first rigid member mounting 125, and the second mounting 167 engages with second rigid member mounting 127. The first rigid mounting 165 is included in or defined by first rigid member arm 130, and the second rigid mounting 167 is included in or defined by second rigid member arm 132. According to some embodiments, the first and second rigid member arms 130, 132 may extend away from face 115 at an angle.

[0086] In some embodiments, the first rigid member mounting 125 includes mounting elements that are configured to engage with opposing sides of the first mounting 165 to secure the first mounting 165 within the first rigid member mounting 125. In some embodiments, the mounting elements of the first rigid member mounting 125 define fastener passage 140 extendingtherethrough, configured to receive a fastener. In some embodiments, the second rigid member mounting 127 includes mounting elements configured to engage with opposing sides of the second mounting 167 to secure the second mounting 167 within the second rigid member mounting 127. In some embodiments, the mounting elements of the second rigid member mounting 127 define fastener passage 142 extending therethrough, configured to receive a fastener.

[0087] According to some embodiments, the flexible member 150 is moveable between a first stable position in which the flexible member 150 is deformable relative to the rigid member 110 to thereby provide a first degree of compliance; and a second stable position in which the flexible member 150 engages the rigid member 110 to constrain movement of the flexible member 150 to thereby provide a second degree of compliance which is lower than the first degree of compliance. According to some embodiments, when the flexible member 150 is in the first stable position, the flexible member 150 has an inverted V-shape relative to the rigid member 110. Additionally, or alternatively, in some embodiments, when the flexible member 150 is in the second stable position, the flexible member 150 is substantially V-shaped relative to the rigid member 110.

[0088] According to some embodiments, providing the first degree of compliance includes the flexible member 150 having a degree of movement relative to the rigid member 110. When the robot appendage engages with the surface, a force may be applied to the flexible member 150, and the flexible member 150 may provide for deformation of its shape due to its elastic characteristics. Accordingly, the mechanism 100 is adaptable to the nature of the interaction between the robot appendage and the surface.

[0089] When the force applied to flexible member 150, such as by the interaction between the robot appendage and the surface being engaged, reaches a predefined threshold force, the flexible member 150 is caused to transition from the first stable position to the second stable position. In some embodiments, transitioning between the first stable position and the second stable position includes a displacement of the flexible member 150, moving it from the configuration as seen in Figure 1A to the configurations shown in Figure IB. As the flexible member 150 is in an equilibrium position when it is in both the first and second table positions, no energy is required to keep the flexible member 150 in its current position. This isadvantageous over solenoid-based mechanisms, which require a constant supply of current to maintain its configuration in at least one of its positions.

[0090] As shown in Figure IB, the rigid member 110 includes valley 145. In some embodiments, the valley 145 is defined by the rigid member arms 130 and 132. In some embodiments, the valley 145 is configured to receive the flexible member 150 therein when the flexible member is in a second stable position, as shown in Figure IB.

[0091] According to some embodiments, the robot appendage may attach to the flexible member 150. The robot appendage may include or define a mounting arrangement configured to engage with the central spine 155. For example, the mounting arrangement may define a passage that corresponds to the spine passage 170, to receive a fastener therethrough. In embodiments where the robot appendage attaches to the flexible member 150, the rigid member 110, or specifically the face 115 may engage with the surface.

[0092] Another example of the mechanism 100 for providing compliance adjustment for a robot appendage (not shown) configured to engage a surface (not shown) will now be described with reference to Figures 2A and 2B. According to some embodiments, the mechanism 100 includes the rigid member 110 and the flexible member 150 as described above in relation to Figures lA to 1C.

[0093] According to some embodiments, the rigid member 110 may be a first rigid member 110, and the mechanism 100 may include a second rigid member 220. The second rigid member 220 may define, first face 225, second face 230, proj ection 240 and / or fastener passage 245. The second rigid member 220 may attach to the flexible member 150 by inserting a fastener through the fastener passage 245 and the spine passage 170. When the second rigid member 220 is attached to the flexible member 150 via the fastener passage 245, and when the flexible member 150 is in the first position, the second rigid member 220 may be pivotable about the axis defined by the fastener passage 245, relative to the first rigid member 110. In this way, the orientation of the second rigid member 220 may be adaptable to the surface when the robot appendage is engaging with the surface when the flexible member 150 is in the first stable position. The second face 230 may be configured to engage with the surface when the mechanism 100 is positioned between the robot appendage and the surface.

[0094] The first face 225 opposes the first rigid member 110, such that, according to some embodiments, when the flexible member 150 is in the second stable position, the first face 225 engages with the first rigid member 110, such that relative movement of the rigid members is substantially restricted. According to some embodiments, the first face 225 may include or define curved surfaces 250, 252 that correspond to the contour or shape of at least a portion of the rigid member 110 and / or flexible member 150. In some embodiments, the shape of the curved surfaces 250, 252 corresponds to the wings 130, 132 and / or first mounting 165 and / or the second mounting 167 respectively. When the flexible member 150 is in the second stable position the curved surface 250 engages with wing 130 and / or first mounting 165. Additionally, or alternatively, when the flexible member 150 is in the second stable position the curved surface 252 engages with wing 132 and / or second mounting 167.

[0095] According to some embodiments, when the flexible member 150 is in the second position, the projection 240 of the second rigid member 220 is received within the valley 145 of the first rigid member 110. When the projection 240 is received within the valley 145, side walls of the projection 240 may contact or abut against opposing portions of the rigid member arms 130, 132 such that the relative movement of the first rigid member 110 and the second rigid member 220 are substantially restricted.

[0096] In some embodiments, when the flexible member 150 is in the second stable position, relative movement of the first rigid member 110 and the second rigid member 220 is restricted by both the first face 225 contacting the first rigid member 110 and the projection 240 contacting the first rigid member 110 while received within the valley 145. In some embodiments, when the flexible member 150 is in the second stable position, the relative movement of the first rigid member 110 and the second rigid member 220 is only restricted by the first face 225 contacting the first rigid member 110. In other embodiments, when the flexible member 150 is in the second stable position, the relative movement of the first rigid member 110 and the second rigid member 220 is only restricted by the projection 240 being received in the valley 145, thereby allowing the side walls of the projection 240 to contact the opposing portions of the rigid member walls 130, 132.

[0097] As shown in Figure 2A, the attachment valley 120 may be configured to receive mounting panel 210. Mounting panel 210 may be used to mount two or more mechanisms 100 in an array.

[0098] According to some embodiments, the robot appendage is attached to the flexible member 150 via the second rigid member 220. In some embodiments, the second rigid member 220 includes or defines a mating structure that is attachable to a corresponding mating structure included in / on and / or defined by the robot appendage. In some embodiments, the robot appendage includes and / or defines the second rigid member 220, and the second rigid member 220 attaches to the flexible member 150.

[0099] According to some embodiments, the mechanism 100 may be provided with, integrated with or otherwise include an actuator configured to move the flexible member 150 between the first and second stable positions. In some embodiments, the actuator may only be configured to return the flexible member 150 to the first stable position from the second stable position. In some embodiments, the actuator is only configured to move the flexible member 150 to the second stable position from the first stable position. In some embodiments, the actuator is configured to move the flexible member 150 between the first and second stable positions at will.

[0100] An of a compliance adjustment mechanism incorporating an actuator will now be described with reference to Figures 4A to 4E.

[0101] In this example, the mechanism 400 includes a rigid member 410 and a flexible member 450 connected to the rigid member 410 via fasteners, such as pins 441, 443, mounted in fastener passages 440, 442. A second rigid member 420 is connected to the flexible member 450 via a fastener, such as a pin 471, provided in spine passage 470.

[0102] In this example, the actuator includes two wires 480, or other flexible members, passing through longitudinally extending slots 485 provided in ends of the rigid member 410, with the wires 480 passing over the pins 441, 443, and under the pin 471. As shown in Figure 4 A, when the flexible member is deformed in the second stable position, the wires 480 engage an underside of the pin 471. When a force is applied to the wires to straighten the wires, as shownby the arrows 481, the wires imparts a force on the pin 471, thereby biasing the flexible member 450 away from the rigid member 410, thereby returning the compliance mechanism to the first stable configuration shown in Figures 4C and 4D.

[0103] It will be appreciated that the applied force need only push the flexible member 450 beyond an inflection point, at which point forces within the flexible member will ensure the flexible member returns to the first stable position. Consequently only a small force is required to cause the flexible member to return to the first stable position.

[0104] The above described arrangement can also incorporate one or more sensors, for example to detect operation of the compliance adjustment mechanism. For example, force, position, movement and / or contact sensors could be used to detect when the flexible member moves from or to one of the stable states, with this optionally being used to control operation of the actuator.

[0105] An example sensor arrangement is shown in Figure 4F.

[0106] In this example, the sensor is provided on a circuit board 490 mounted on the rigid member 410, between the rigid member 410 and the flexible member 450. The sensor can be configured to measure a distance between the rigid and flexible members, so that the sensor effective measures the height of the second rigid member 420. This allows a processing device, such as a controller or similar, to determine if the flexible member 450 is in the first or second position, and hence whether the compliance adjustment mechanism has been toggled and a reset is necessary. The sensor could also potentially be used to measure contact deformation to gain information of a grasped object or environmental properties (e.g. elevation of the ground) from how much the switches are depressed). Additionally, and / or alternatively, the sensor could measure a pressure, allowing the sensor to determine an engagement force with the a surface, which in turn can be used to ensure a surface is suitable engaged.

[0107] An example of the deformation the flexible member undergoes when moving from the first to the second stable positions is shown in Figures 5A to 5E, with corresponding stresses within the compliance mechanism being shown in Figures 6A to 6E and Figures 7A and 7B.This highlights that stresses within the compliance mechanism are manageable, allowing for repeated operation of the compliance mechanism.

[0108] The compliance mechanism can incorporate and / or be attached to a variety of different surface engaging members configured to engage a surface. The surface engaging members can be used to modify a surface engagement, for example increasing surface engagement to facilitate movement of robot or vehicle over a surface, and example surface engaging members could include high friction materials, hooks, spikes or mechanical locking arrangements, or the like.

[0109] An example of a grabber incorporating surface engagement members will now be described with reference to Figures 8A to 8D.

[0110] In this example, the grabber 890, includes three arms 892 mounted to a hub 893 attached to a manipulator arm 891. It will be appreciated that the nature of the grabber 890 is not important for illustration of the invention and this will not therefore be described in detail.[oni] In this example, each arm includes a number of flexibly connected compliance adjustment mechanisms 800, each including a rigid member 810 and flexible member 850. Each flexible member 850 is attached to a hook 895 mounted to a fastener pin 871, with the hook engaging with a surface to thereby deform the corresponding flexible member, which in turn positions the hook to engage with the surface. Through suitable configuration of the hook, this can be used so that the hooks engage and grasp surface asperities, so that the grabber is secured to a surface, such as an object being grasped.

[0112] Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. As used herein and unless otherwise stated, the term "approximately" means ±20%.

[0113] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent topersons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A mechanism for providing compliance adjustment for a robot appendage configured to engage a surface, the mechanism including: a rigid member; and a flexible member connected to the rigid member, the flexible member being moveable between: a first stable position in which the flexible member is deformable relative to the rigid member to thereby provide a first degree of compliance; and a second stable position in which the flexible member is deformed to constrain movement of the flexible member to thereby provide a second degree of compliance which is lower than the first degree of compliance, wherein the mechanism is attached to the robot appendage to provide a first or second degree of compliance when the robot appendance engages the surface.

2. The mechanism of claim 1, wherein in the second stable position the flexible member engages the rigid member.

3. The mechanism of claim 1 or claim 2, wherein at least one of: the mechanism is attached to the robot appendage so that the mechanism is provided between the robot appendage and the surface; the robot appendage is attached to the rigid member; the rigid member is part of the robot appendage; the robot appendage is attached to the flexible member; or the rigid member is a first rigid member and the robot appendage is attached to the flexible member via a second rigid member.

4. The mechanism of claim 1, wherein the rigid member is a first rigid member and a second rigid member is attached to the flexible member.

5. The mechanism of claim 4, wherein the first and second rigid members engage with each other such that their relative movement is substantially restricted in the second stable position.

6. The mechanism of claim 5, wherein the first rigid member includes a valley configured to receive a projection of the second rigid member, wherein when the projection is received within the valley, the projection engages with the valley to restrict relative movement of the rigid members.

7. The mechanism of claim 5 or claim 6, wherein the second rigid member includes a plate defining a first face that opposes the first rigid member.

8. The mechanism of claim 7, wherein when the flexible member is in the second stable position, at least a portion of the first face contacts at least a portion of the first rigid member, thereby restricting the relative movement of the rigid members.

9. The mechanism of any one of the preceding claims, wherein the flexible member includes first and second mountings proximate opposing ends of the flexible member, wherein the first and second mountings are configured to couple the flexible member to the rigid member.

10. The mechanism of any one of the preceding claims, wherein the flexible member includes: a central spine; and a first arm extending from the spine supporting the first mounting and a second arm extending from the spine supporting the second mounting.

11. The mechanism of claim 10, wherein a second rigid member is connected to the central spine.

12. The mechanism of claim 11, wherein the second rigid member is pivotably mounted to the spine to allow an orientation of the second rigid member to adapt when engaging the surface in at least the first stable position.

13. The mechanism of any one of claims 5 to 12, wherein the second rigid member is configured to engage the surface and wherein the second rigid member is pivotally mounted to the flexible member so that the second member aligns with the surface during engagement.

14. The mechanism of any one of the preceding claims, wherein: in the first stable position, the flexible member has an inverted V-shape; and in the second stable position, the flexible member is substantially V-shaped.

15. The mechanism of any one of the preceding claims, wherein the rigid member includes first and second rigid member mountings proximate opposing ends of the rigid member, wherein the first and second rigid member mountings are configured to couple the flexible member to the rigid member.

16. The mechanism of any one of the preceding claims, wherein the rigid member includes a base and rigid member arms extending at an angle from the base.

17. The mechanism of any one or more of the preceding claims, wherein the flexible member is caused to be moved between the first and second stable positions by applying a force to the flexible member.

18. The mechanism of claim 17, wherein the force required to move the flexible member between the first and second stable positions depends on one or more of: a material of the flexible member; dimensions of the flexible member; a thickness of at least part of the flexible member; dimensions of first and second arms of the flexible member; anda shape of the flexible member; an angle of a V-shape of the flexible member.

19. The locking mechanism of any one or more of the preceding claims, wherein an actuator is provided to return the flexible member to the first stable position.

20. The mechanism of any one of claims 5 to 19, wherein the first rigid member is configured to engage with the surface.

21. The mechanism of claim 20, wherein the second rigid member is configured to attach to the robot appendage.

22. The mechanism of claim 20, wherein the robot appendage defines the second rigid member.

23. The mechanism of any one of claims 5 to 19, wherein the second rigid member is configured to engage with the surface.

24. The mechanism of claim 23, wherein the first rigid member is configured to attach to the robot appendage.

25. The mechanism of claim 23, wherein the robot appendage defines the first rigid member.

26. The mechanism of any one of the preceding claims, wherein the flexible member is formed from a material selected from: plastic; polymer; or metal.

27. The mechanism of any one of the claims 1 to 26, wherein the mechanism includes a sensor configured to detect operation of the mechanism.

28. The mechanism of claim 27, wherein the sensor is configured to detect if the flexible member is in the first stable position or second stable position.

29. The mechanism of any one of claims 1 to 28, wherein the mechanism includes a surface engaging member configured to engage a surface.

30. A device including a plurality of the mechanisms according to any one of claims 1 to 29, wherein each of the plurality of the mechanisms are attached to at least one other mechanism of the plurality of mechanisms.

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