Wearable exoskeleton device

Abstract

A wearable exoskeleton device (2) comprising a compliant mechanism (11) and at least one force element (12a-d, 13a-e) configured to exert a force on the compliant mechanism (11) to assist or support a desired articulation of a joint of the body of a wearer of the wearable exoskeleton device (2). The compliant mechanism (11) is configured to resist articulations that are outside the desired articulation and substantially freely allow the desired articulation. A method of fabricating the device (2) comprising forming the compliant mechanism using additive manufacturing.

Description

[0001] WEARABLE EXOSKELETON DEVICE

[0002] TEHCNICAL FIELD

[0003] The present invention relates to a wearable exoskeleton device and a method of fabricating a wearable exoskeleton device.

[0004] BACKGROUND

[0005] A wearable exoskeleton device may be used to assist or support articulation of one or more joints of the body of a wearer of the device. A wearable exoskeleton device may be used by a patient with reduced mobility, for example as a result of a musculoskeletal disability or injury, or to increase the muscular strength or endurance of a wearer of the device.

[0006] A wearable exoskeleton device configured to assist articulation may be considered an ‘active’ device. An active device may be configured to exert an actuation force on the body of a wearer of the device to assist articulation of one or more joints. A known active wearable exoskeleton device may comprise a rigid mechanism and one or more actuators. In use, the one or more actuators may exert forces on the rigid mechanism to assist articulation of one or more joints of the body of a wearer of the device. The rigid mechanism may not freely allow a desired articulation of the one or more joints, for example due to misalignment of the rigid mechanism with the joint. This may restrict natural movement of the wearer, which could result in injury after long-term use of the device.

[0007] Another known active wearable exoskeleton device may comprise a compliant mechanism and one or more force elements. In use, the one or more force elements may exert forces on the compliant mechanism to assist articulation of one or more joints of the body of a wearer of the device. The compliant mechanism may not be configured to resist articulations that are outside of a desired articulation, such that the compliant mechanism and one or more force elements alone are not capable of effectively assisting the desired articulation. An additional rigid mechanism may be required to resist articulations that are outside of the desired articulation.

[0008] A wearable exoskeleton device configured to support articulation may be considered a ‘passive’ device. A passive device may be configured to exert a support force on the body of a wearer of the device in reaction to a force generated by one or more muscles of the body of the wearer to support articulation of one or more joints. A known passive wearable exoskeleton device may comprise a rigid mechanism and one or more force elements. In use, the one or more force elements may exert a support force on the rigid mechanism to support an articulation of a joint of the body of a wearer of the device. The rigid mechanism may have the same limitations as the rigid mechanism described above.

[0009] There is a need for a wearable exoskeleton device which overcomes one or more limitations of known wearable exoskeleton devices.

[0010] SUMMARY

[0011] A first aspect provides a wearable exoskeleton device. The wearable exoskeleton device comprises a compliant mechanism and at least one force element. The at least one force element is configured to exert a force on the compliant mechanism.

[0012] The at least one force element may be configured to exert a force on the compliant mechanism to assist or support a desired articulation of a joint of the body of a wearer of the wearable exoskeleton device. The compliant mechanism may be configured to: i) resist articulations that are outside the desired articulation; and / or ii) substantially freely allow the desired articulation.

[0013] The device may comprise an actuator comprising the compliant mechanism and the at least one force element. The at least one force element may be configured to exert an actuation force on the compliant mechanism to assist the desired articulation. The device comprising the actuator may be used by patients with reduced mobility, i.e., a patient who is not able to affect a desired articulation of a joint through a force generated by the patient’s muscles alone.

[0014] The device may comprise a support element comprising the compliant mechanism and the at least one force element. The at least one force element may be configured to exert a support force on the compliant mechanism to support the desired articulation. The device comprising the support element may be used during rehabilitation by patients with an injury, for example to provide stability of a joint during a desired articulation of the joint. A second aspect provides an actuator for a wearable exoskeleton device. The actuator comprises a compliant mechanism and at least one force element. The at least one force element is configured to exert an actuation force on the compliant mechanism.

[0015] A third aspect provides a support element for a wearable exoskeleton device. The support element comprises a compliant mechanism and at least one force element. The at least one force element is configured to exert a support force on the compliant mechanism.

[0016] The following statements may apply to either the first, second, or third aspects introduced above unless stated otherwise:

[0017] The at least one force element may be configured to exert an actuation force on the compliant mechanism to assist the desired articulation and / or exert a support force on the compliant mechanism to support the desired articulation. The at least one force element may comprise at least one force element configured to exert an actuation force on the compliant mechanism to assist the desired articulation and at least one force element configured to exert a support force on the compliant mechanism to support the desired articulation.

[0018] A compliant mechanism is a structure that transmits force through elastic deformation of at least part of the structure. In use, the at least one force element may exert a force on the compliant mechanism, causing elastic deformation of at least part of the compliant mechanism. The compliant mechanism, in turn, may exert a force on a part of the body of the wearer connected to the joint to assist or support the desired articulation of the joint, thereby assisting or supporting a desired movement of the part of the body. Preferably, the device exerts the force on the part of the body by means of elastic deformation of at least part of the compliant mechanism alone.

[0019] By resisting articulations that are outside the desired articulation, the compliant mechanism constrains the direction of the force exerted on the compliant mechanism by the at least one force element to effectively assist or support the desired articulation. By substantially freely allowing the desired articulation, the device substantially allows natural movement of the wearer. Where applicable, the at least one force element is preferably configured to exert the support force on the compliant mechanism to further resist articulations that are outside the desired articulation. The support force may be a reaction force in reaction to a force exerted on the compliant mechanism by a wearer of the device. The force exerted on the compliant mechanism by a wearer of the device may be a force generated by one or more muscles of the body of a wearer of the device.

[0020] The at least one force element may be configured to exert the support force on the compliant mechanism to resist the desired articulation. In such examples, the device may be used during rehabilitation or exercise to strengthen muscles which are used to affect the desired articulation.

[0021] The compliant mechanism may comprise a first stiffness and a second stiffness. The first stiffness may define the extent to which the compliant mechanism resists deformation in response to a force to affect the desired articulation. The second stiffness may define the extent to which the compliant mechanism resists deformation in response to a force to affect articulations that are outside the desired articulation. The second stiffness may be greater than the first stiffness.

[0022] The compliant mechanism is preferably stiffer in resistance to forces which affect articulations that are outside the desired articulation than in resistance to forces which affect the desired articulation. The compliant mechanism is preferably relatively flexible with respect the desired articulation and relatively stiff with respect articulations that are outside the desired articulation.

[0023] The compliant mechanism may be thicker in the direction of a force to affect articulations that are outside the desired articulation than in the direction of a force to affect the desired articulation.

[0024] The device may comprise a first stiffness and a second stiffness. The first stiffness may define the extent to which the device resists a force to affect the desired articulation. The second stiffness may define the extent to which the device resists a force to affect articulations that are outside the desired articulation. The second stiffness may be greater than the first stiffness. The first stiffness may be in the order of IO N. The second stiffness may be in the order of 100 N. The second stiffness may be a product of the first stiffness and an integer, wherein the integer is 2, 4, 5, 10, 15, or 20, or within a range defined by any two of these values.

[0025] The first and / or second stiffness may increase when the at least one force element exerts a force on the compliant mechanism relative to when the at least one force element does not exert a force on the compliant mechanism. The first and / or second stiffness may increase when the at least one force element is arranged to exert a force on the compliant mechanism relative to when the at least one force element is not arranged to exert a force on the compliant mechanism.

[0026] A force to affect the desired articulation may be the actuation force exerted on the compliant mechanism by the at least one force element and / or a force exerted by one or more muscles of a wearer of the device.

[0027] The compliant mechanism may be configured to allow for an initial misalignment between the compliant mechanism and a joint of the body of a wearer of the device. The compliant mechanism may constrain the direction of the force exerted on the compliant mechanism by the at least one force element, thereby effectively assisting or supporting a desired articulation of the joint, while accommodating for any initial misalignment between the compliant mechanism and the joint.

[0028] The force exerted on the compliant mechanism by the or each force element may comprise a distributed force. This may improve the transmission of force to the body of a wearer of the device to assist or support a desired articulation.

[0029] The compliant mechanism may be compliant in three dimensions. With respect to a wearer of the device in use, the compliant mechanism may be compliant in a plane parallel to the sagittal plane, out of the plane parallel to the sagittal plane with respect to shear forces, and out of the plane parallel to the sagittal plane with respect to torsional forces. This advantageously improves comfort for the wearer of the device.

[0030] The compliant mechanism may be compliant within a first plane of motion which may correspond to a normal plane of motion of a human or animal joint. The compliant mechanism may further be compliant in a second plane of motion which may correspond to motion out of plane of the normal plane of motion. The compliant mechanism may be more compliant within the first plane than within the second plane.

[0031] A desired articulation of a joint may be an articulation that is within a normal range of motion of the joint. Articulations that are outside a desired articulation may comprise articulations beyond a normal range of motion of the joint. Articulations outside the desired articulation may comprise hyperextension, articulations which are misaligned with the normal alignment of the joint, and / or articulations outside a normal plane of movement of the joint. As used herein, “normal” may refer to an average healthy joint or may refer to the normal behaviour of a joint of a particular human or animal or a particular wearer of the device.

[0032] The at least one force element may comprise a plurality of force elements. Each force element of the plurality of force elements may be configured to exert a force on the compliant mechanism to cause deformation of the compliant mechanism in a different direction. The plurality of force elements may comprise a plurality of sets of force elements. Each set of force elements may be configured to exert a force on the compliant mechanism to cause deformation of the compliant mechanism in a different direction. The different directions may comprise at least one first and second opposite directions.

[0033] The compliant mechanism may comprise a compliant scissor mechanism. This may improve the transmission of force to the body of a wearer of the device to assist or support a desired articulation.

[0034] The compliant mechanism may comprise at least one compliant mechanism unit. The compliant mechanism unit may comprise a plurality of longitudinal compliant elements and a plurality of compliant joints. The plurality of longitudinal compliant elements may be connected together by the plurality of compliant joints. The compliant mechanism unit may consist essentially of the plurality of longitudinal compliant elements and the plurality of compliant joints. The plurality of longitudinal compliant elements may be arranged to define an enclosed space.

[0035] The plurality of longitudinal compliant elements and the plurality of compliant joints may be integral. The plurality of longitudinal compliant elements and the plurality of compliant joints may be formed integrally. The plurality of longitudinal compliant elements and the plurality of compliant joints may be formed as a single part. The plurality of longitudinal compliant elements and the plurality of compliant joints may be formed by means of additive manufacturing.

[0036] At least one of the plurality of compliant joints may be less stiff than at least one of the plurality of longitudinal compliant elements with respect to a force applied to the compliant mechanism unit. Each of the plurality of compliant joints may be less stiff than each of the plurality of longitudinal compliant elements with respect to a force applied to the compliant mechanism unit. As such, the force applied to the compliant mechanism unit may cause one or more of the plurality of longitudinal compliant elements to pivot about one or more of the plurality of compliant joints. The force applied to the compliant mechanism unit may be an actuation force, a support force, or any other force described herein.

[0037] At least one of the plurality of compliant joints may be thinner than at least one of the plurality of longitudinal compliant elements in the direction of a force applied to the compliant mechanism unit. Each of the plurality of compliant joints may be thinner than each of the plurality of longitudinal compliant elements in the direction of a force applied to the compliant mechanism unit. The force applied to the compliant mechanism unit may be an actuation force, a support force, or any other force described herein.

[0038] The or each compliant joint may comprise a first cross-section. The first cross-section may be rectangular. The first cross-section may comprise a curve. The first cross-section may comprise a first curve and a second curve. The second curve may be inverted with respect to the first curve.

[0039] The or each longitudinal compliant element may be configured to pivot about a respective compliant joint when a force is applied to the longitudinal compliant element. The force applies to the longitudinal compliant element may be an actuation force, a support force, or any other force described herein. The first cross-section of the or each compliant joint may be a cross-section as viewed in a direction perpendicular to a plane in which the or each longitudinal compliant element is configured to pivot about a respective compliant joint. The or each compliant mechanism unit may comprise four longitudinal compliant elements. The or each compliant mechanism unit may comprise four compliant joints. The four longitudinal compliant elements may, in at least one configuration, form the sides of a nominal geometric kite, wherein the four compliant joints form the vertices of the nominal geometric kite. The at least one configuration may comprise an extended configuration of the compliant mechanism. The longitudinal compliant elements may be of equal length. The nominal geometric kite may be a nominal geometric rhombus. The longitudinal compliant elements may comprise two pairs of longitudinal compliant elements of equal length, wherein the length of the longitudinal compliant elements of one of the pairs of longitudinal compliant elements is different to the length of the longitudinal compliant elements of the other pair of longitudinal compliant elements.

[0040] Where the compliant mechanism comprises more than one compliant mechanism unit, the compliant mechanism may comprise one or more first compliant mechanism unit, wherein the longitudinal compliant elements of the or each first compliant mechanism unit are of equal length, and one or more second compliant mechanism unit, wherein the longitudinal compliant elements of the or each second compliant mechanism unit comprise two pairs of longitudinal compliant elements of equal length, wherein the length of the longitudinal compliant elements of one of the pairs of longitudinal compliant elements is different to the length of the longitudinal compliant elements of the other pair of longitudinal compliant elements. The compliant mechanism may comprise any combination of any of the compliant mechanism units described herein depending on the application of the device.

[0041] The at least one compliant mechanism unit may comprise a plurality of compliant mechanism units. The compliant mechanism may comprise at least one compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit. The at least one compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be formed integrally with the plurality of compliant mechanism units. The plurality of compliant mechanism units and the at least one compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be formed as a single part. The plurality of compliant mechanism units and the at least one compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be formed by means of additive manufacturing. The compliant mechanism may consist essentially of the plurality of compliant mechanism units and the at least one compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit.

[0042] The compliant mechanism may therefore comprise a single part formed of a single compliant material. The material of the compliant mechanism may be thicker in the direction of a force to affect articulations that are outside the desired articulation than in the direction of a force to affect the desired articulation. The material of the compliant mechanism may therefore be stiffer in resistance to forces which affect articulations that are outside the desired articulation than in resistance to forces which affect the desired articulation.

[0043] In other examples, each of the compliant mechanism units may be at least partially rigid and / or non-compliant relative to the at least one compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit. For example, one or more of the longitudinal compliant elements of each of the compliant mechanism units may instead be a rigid or non-compliant longitudinal element, such that each of the compliant mechanism units comprises one or more rigid or non-compliant longitudinal element connected to an adjacent longitudinal element by a compliant joint.

[0044] The or each compliant mechanism unit and / or the or each compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be formed of thermoplastic polyurethane (TPU). In other examples, other suitable materials may be used.

[0045] The or each compliant mechanism unit and / or the or each compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be formed of a material comprising a Young’s modulus of less than or equal to 10 GPa. The Young’s modulus may be less than or equal to 9 GPa, 8 GPa, 7 GPa, 6 GPa, 5 GPa, 4 GPa, 3 GPa, 2 GPa, or 1 GPa, or within a range between any two of these values. The Young’s modulus may be less than or equal to 1 GPa, 0.9 GPa, 0.8 GPa, 0.7 GPa, 0.6 GPa, 0.5 GPa, 0.4 GPa, 0.3 GPa, 0.2 GPa, or 0.1 GPa, or within a range between any two of these values. The Young’s modulus may be less than or equal to 0.1 GPa, 0.09 GPa, 0.08 GPa, 0.07 GPa, 0.06 GPa, 0.05 GPa, 0.04 GPa, 0.03 GPa, 0.02 GPa, or 0.01 GPa, or within a range between any two of these values. The Young’s modulus may be less than or equal to 10 MPa, 9 MPa, 8 MPa, 7 MPa, 6 MPa, 5 MPa, 4 MPa, 3 MPa, 2 MPa, or 1 MPa, or within a range between any two of these values. The Young’s modulus may be less than or equal to 1 MPa, 0.9 MPa, 0.8 MPa, 0.7 MPa, 0.6 MPa, 0.5 MPa, 0.4 MPa, 0.3 MPa, 0.2 MPa, or 0.1 MPa, or within a range between any two of these values.

[0046] The or each compliant mechanism unit and / or the or each compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be formed of a material comprising a hardness of between 10A and 80A on the Shore A Hardness Scale.

[0047] The one or more compliant mechanism units advantageously allows for customisation of the design of the wearable exoskeleton device, where the device can be designed with a suitable number of compliant mechanism units for a particular application.

[0048] The or each compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be less stiff than the adjacent compliant mechanism units with respect to a force applied to at least one of the adjacent compliant mechanism units. The or each compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be less stiff than the plurality of longitudinal compliant elements of at least one of the adjacent compliant mechanism units with respect to a force applied to at least one of the adjacent compliant mechanism units. A force applied to one of the compliant mechanism units may cause the compliant mechanism unit to pivot about the or each compliant joint connecting the compliant mechanism unit to an adjacent compliant mechanism unit. The force applied to at least one of the adjacent compliant mechanism units may be an actuation force, a support force, or any other force described herein.

[0049] The or each compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be thinner than the adjacent compliant mechanism units in the direction of a force applied to at least one of the adjacent compliant mechanism units. The or each compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit may be thinner than the plurality of longitudinal compliant elements of at least one of the adjacent compliant mechanism units in the direction of a force applied to at least one of the adjacent compliant mechanism units. The force applied to at least one of the adjacent compliant mechanism units may be an actuation force, a support force, or any other force described herein.

[0050] The at least one force element may comprise at least one force element arranged between each compliant mechanism unit and an adjacent compliant mechanism unit. The at least one force element may comprise first and second force elements. The first and second force elements may be arranged on opposite sides of the at least one compliant joint connecting the adjacent compliant mechanism units. The first force element may be configured to exert a first force on the compliant mechanism between adjacent compliant mechanism elements to cause at least one of the adjacent compliant mechanism elements to pivot about the compliant joint connecting the adjacent compliant mechanism units in a first direction. The second force element may be configured to exert a second force on the compliant mechanism between adjacent compliant mechanism elements to cause at least one of the adjacent compliant mechanism elements to pivot about the compliant joint connecting the adjacent compliant mechanism units in a second direction, opposite the first direction.

[0051] The at least one force element may comprise at least one inflatable chamber. The at least one inflatable chamber may comprise at least one inflatable pneumatic chamber and / or at least one inflatable hydraulic chamber. The at least one inflatable hydraulic chamber may alternatively be referred to as at least one expandable chamber or at least one expandable hydraulic chamber. The or each inflatable chamber may be formed from a flexible material. The flexible material may comprise a flexible fabric material. The flexible fabric material may comprise a TPU-coated nylon fabric. In other examples, the flexible fabric material may comprise an alternative material.

[0052] Where applicable, the at least one inflatable chamber may be arranged to exert a support force on the compliant mechanism when inflated. The at least one inflatable chamber may be arranged such that the at least one inflatable chamber does not exert a support force on the compliant mechanism when the at least one inflatable chamber is not inflated.

[0053] In other examples, the at least one force element may comprise at least one electrical force element, such as a dielectric elastomer actuator, and / or at least one thermal force element, such as a shape memory polymer or a shape memory alloy. The at least one inflatable chamber may comprise at least one lateral inflatable chamber arranged between each compliant mechanism unit and an adjacent compliant mechanism unit. The or each lateral inflatable chamber may be arranged outside of the enclosed space of the respective adjacent compliant mechanism units. Where the or each compliant mechanism unit comprises four longitudinal compliant elements and where the longitudinal compliant elements comprise two pairs of longitudinal compliant elements of equal length, with the length of the longitudinal compliant elements of one of the pairs of longitudinal compliant elements different to the length of the longitudinal compliant elements of the other pair of longitudinal compliant elements, the or each lateral inflatable chamber may be arranged between the longer longitudinal compliant elements of the respective adjacent compliant mechanism units. The at least one lateral inflatable chamber may additionally or alternatively comprise a lateral inflatable chamber arranged between the shorter longitudinal compliant elements of the respective adjacent compliant mechanism units.

[0054] The plurality of compliant mechanism units may comprise three or more compliant mechanism units. Where the at least one inflatable chamber comprises a lateral inflatable chamber arranged between each compliant mechanism unit and an adjacent compliant mechanism unit, the lateral inflatable chambers may be in fluid communication with each other. In other examples, the lateral inflatable chambers may be fluidly separate.

[0055] The at least one lateral inflatable chamber may comprise first and second lateral inflatable chambers. The first and second lateral inflatable chambers may be arranged on opposite sides of the at least one compliant joint connecting the adjacent compliant mechanism units. Where the plurality of compliant mechanism units comprises three or more compliant mechanism units, the at least one lateral inflatable chamber may comprise first and second lateral inflatable chambers arranged between each compliant mechanism unit and an adjacent compliant mechanism unit. The first lateral inflatable chambers may be in fluid communication with each other. The second lateral inflatable chambers may be in fluid communication with each other. In other examples, the first and / or second lateral inflatable chambers may be fluidly separate. The at least one force element may comprise at least one central force element. The at least one central force element may be configured to exert a force on the compliant mechanism along a central longitudinal axis of the compliant mechanism. The at least one central force element may be configured to exert a force on the compliant mechanism to extend and / or retract the compliant mechanism in a longitudinal direction.

[0056] The at least one inflatable chamber may comprise a central inflatable chamber arranged within the enclosed space of the or each compliant mechanism unit. Where the at least one compliant mechanism unit comprises a plurality of compliant mechanism units, the at least one inflatable chamber may comprise a central inflatable chamber arranged within the enclosed space of each compliant mechanism unit. The central inflatable chambers may be in fluid communication with each other. In other examples, the central inflatable chambers may be fluidly separate.

[0057] In examples comprising the support element, a wearer of the device may exert a force on the compliant mechanism when affecting a desired articulation of a joint. The compliant mechanism will in turn exert a force on the plurality of inflatable chambers. As a result, this may cause fluid to move between the inflatable chambers in fluid communication with each other. The or each inflatable chamber receiving fluid from another inflatable chamber will expand, thereby exerting a force on the compliant mechanism. This force exerted on the compliant mechanism may provide the support force.

[0058] The compliant mechanism may comprise two layers. The two layers may be substantially identical. When assembled, each of the two layers may be parallel to a plane parallel to a longitudinal axis of each longitudinal compliant element of the or each compliant mechanism unit.

[0059] The two layers may comprise a first layer and a second layer. The first layer may comprise a first longitudinal portion of each longitudinal compliant element and a first portion of each compliant joint of the or each compliant mechanism unit. The first longitudinal portion of each longitudinal compliant element and the first portion of each compliant joint may be formed integrally. The first layer may be formed as a single part. The first layer may be formed by means of additive manufacturing. The second layer may comprise a second longitudinal portion of each longitudinal compliant element and a second portion of each compliant joint of the or each compliant mechanism unit. The second longitudinal portion of each longitudinal compliant element and the second portion of each compliant joint may be formed integrally. The second layer may be formed as a single part. The second layer may be formed by means of additive manufacturing.

[0060] The two layers may be formed separately. The two separate layers may be fastened together. The two separate layers may be fastened together such that when a force is exerted on the compliant mechanism, the two layers deform together. In another example, the two layers may be formed integrally with each other. The compliant mechanism may comprise one or more integral joints holding the two layers together.

[0061] Any of the inflatable chambers described herein may be sandwiched between the two layers. The or each of the central inflatable chambers may be sandwiched between the two layers of a respective compliant mechanism unit. Any of the inflatable chambers described herein may comprise at least one tab sandwiched between the two layers. The at least one tab may be sandwiched between parts of the two layers forming one of the plurality of longitudinal compliant elements.

[0062] The wearable exoskeleton device may comprise control means to control the force exerted on the compliant mechanism by the or each force element. Where the at least one force element comprises two or more force elements, the control means may be configured to control the force exerted on the compliant mechanism by each force element independently. Where the at least one force element comprises first and second force elements arranged on opposite sides of at least one compliant joint connecting adjacent compliant mechanism units, the control means may be configured to control the force exerted on the compliant mechanism by the or each first force element independently of the force exerted on the compliant mechanism by the or each second force element. Where the at least one force element comprises a plurality of sets of force elements, the control means may be configured to control each set of force elements independently.

[0063] The control means may comprise one or more force sensors configured to determine a magnitude of one or more forces exerted on the compliant mechanism by the or each force element. The control means may be configured to control the or each force element to exert a force comprising a target magnitude on the compliant mechanism. The control means may be configured to determine an actual magnitude of a force exerted on the compliant mechanism by the or each force element, compare the actual magnitude with the target magnitude, and adjust one or more control inputs to the or each force element in dependence on the comparison to match the actual magnitude to the target magnitude.

[0064] The wearable exoskeleton device may comprise control means to control the pressure of a fluid within the or each inflatable chamber to control the force exerted on the compliant mechanism by the or each inflatable chamber. Where the lateral inflatable chambers and / or the central inflatable chambers are fluidly separate, the device may comprise control means to control the pressure of a fluid within each lateral inflatable chamber and / or each central inflatable chamber independently.

[0065] In examples comprising the actuator, the control means may comprise a control system comprising a pump, one or more valves, and a controller configured to control the pump and the one or more valves. The one or more valves may comprise any valve operable in response to an electrical signal, such as a digital valve or solenoid valve. In some examples, the control system may comprise more than one pump. The or each pump may comprise a compressor, a motor-driven piston, or any other suitable arrangement. In another example, the control system may comprise a source of compressed fluid, such as a compressed air tank or reservoir, one or more valves, and a controller configured to control the one or more valves to control a release of fluid from the source of compressed fluid.

[0066] The control system may comprise one or more pressure sensors configured to determine the fluid pressure within the or each inflatable chamber. The one or more pressure sensors may be configured to determine the fluid pressure within the or each inflatable chamber and output one or more signals indicative of the fluid pressure to the controller. This provides a feedback loop to the controller such that the controller can control the pump and the one or more valves to obtain a desired fluid pressure within the or each inflatable chamber. In addition, or alternatively, to the one or more pressure sensors, the control system may comprise one or more force sensors as described above. This may provide an additional or alternative feedback loop to the controller.

[0067] The control system may comprise one or more sensors configured to measure movement of a wearer of the device. The one or more sensors may comprise a sensor array comprising a plurality of sensors. The plurality of sensors may be configured to measure movement of a wearer of the device. The movement of the wearer may comprise a desired articulation. The control system may comprise a memory configured to store a set of instructions for operation of the device. The controller may be configured to provide inputs to the pump and / or the one or more valves in dependence on one or more signals from the one or more sensors and / or in dependence on the set of instructions.

[0068] In examples comprising the support element, the control means may comprise one or more manually operated valves. The or each manually operated valve may be operable in a first configuration in which a fluid, such as air, is permitted to flow through the valve into the respective inflatable chamber. The or each manually operated valve may be operable in a second configuration in which a fluid is permitted to flow out of the respective inflatable chamber through the valve. A fluid may be substantially prevented from flowing out of the respective inflatable chamber through the valve when the valve is in the first configuration. The or each manually operated valve may be operable in a third configuration in which a fluid is substantially prevented from flowing out of the respective inflatable chamber through the valve and in which a fluid is substantially prevented from flowing into the respective inflatable chamber through the valve.

[0069] The or each manually operated valve may be manually reconfigurable between the first and second configurations. Where applicable, the or each manually operated valve may be manually reconfigurable between the first, second, and third configurations. The or each valve may be configured to be attached to a pump, e.g., a manual or mechanically driven pump, to pump air into the respect inflatable chamber with the valve in the first configuration.

[0070] In other examples, the one or more manually operated valves may be replaced by one or more electronic and / or remotely operated valves. The or each electronic and / or remotely operated valve may be operable in the first configuration and / or the second configuration and / or the third configuration described in the preceding paragraph. The or each electronic and / or remotely operated valve may be electronically and / or remotely reconfigurable between the first and second configurations, and / or the first, second, and third configurations as applicable.

[0071] In examples comprising first and second lateral inflatable chambers, the control means to control a pressure of a fluid may be configured to control the pressure of a fluid within the or each first lateral inflatable chamber independently of a pressure of a fluid within the or each second lateral inflatable chamber. In use, inflation of the or each first lateral inflatable chamber may cause the or each compliant mechanism unit to pivot in a first direction about the or each compliant joint connecting the compliant mechanism unit to an adjacent compliant mechanism unit, causing the compliant mechanism to bend in the first direction. Inflation of the or each second lateral inflatable chamber may cause the or each compliant mechanism unit to pivot in a second direction, opposite the first direction, about the or each compliant joint connecting the compliant mechanism unit to an adjacent compliant mechanism unit, causing the compliant mechanism to bend in the second direction. The compliant mechanism may in turn exert a force on a part of the body of the wearer connected to a joint to assist a desired articulation of the joint in the first or second direction, respectively.

[0072] The or each first lateral inflatable chamber and the or each second lateral inflatable chamber may be configured to inflate to a maximum inflation volume. The maximum inflation volume of the or each first lateral inflatable chamber may be greater than the maximum inflation volume of the each second lateral inflatable chamber, or vice versa. For example, where the desired articulation is extension or flexion of a joint, such as a knee joint, the device may be configured such that inflation of the or each first lateral inflatable chamber assists extension of the joint and inflation of the or each second lateral inflatable chamber assists flexion of the joint. The maximum inflation volume of the or each second lateral inflatable chamber may be less than the maximum inflation volume of the or each first lateral inflatable chamber because the range of flexion is less than the range of extension.

[0073] The maximum inflation volume of the or each lateral inflatable chamber may be selected to inhibit articulations outside the desired articulation. The maximum inflation volume of the or each second lateral inflatable chamber may be selected to inhibit hyperflexion and / or the maximum inflation volume of the or each first lateral inflatable chamber may be selected to inhibit hyperextension, or vice versa.

[0074] In examples comprising a central inflatable chamber arranged within the enclosed space of the or each compliant mechanism unit, the control means to control a pressure of a fluid may be configured to control the pressure of a fluid within the or each central inflatable chamber independently of a pressure of a fluid within the or each lateral inflatable chamber. In examples comprising a plurality of compliant mechanism units, the control means may be configured to control the pressure of a fluid within each central inflatable chamber independently. Inflating the or each central inflatable chamber may cause the plurality of longitudinal compliant elements of the or each compliant mechanism unit to pivot about the respective plurality of compliant joints, causing the compliant mechanism to extend in a direction parallel to a longitudinal axis of the compliant mechanism.

[0075] The or each central inflatable chamber may be inflated to extend the compliant mechanism to conform the device to the body of a wearer of the device. Inflating the or each central inflatable chamber may also increase a stiffness of the device to improve force transmission.

[0076] The or each central inflatable chamber may be configured to inflate to a maximum inflation volume. The maximum inflation volume of the or each central inflatable chamber may be selected to inhibit articulations outside the desired articulation.

[0077] The compliant mechanism is inherently resiliently biased towards a rest position by means of an inherent restoring force. As such, removal of a force exerted by the at least one force element on the compliant mechanism, for example through deflation of any of the inflatable chambers described above, in the absence of any other force exerted on the compliant mechanism, will cause the compliant mechanism to return towards the rest position. Where the compliant mechanism comprises at least one compliant mechanism unit, the inherent restoring force may be primarily generated by the compliant joints connecting the plurality of longitudinal compliant elements of the or each compliant mechanism unit and / or the or each compliant joint connecting adjacent compliant mechanism units. At least a portion of a length of the compliant mechanism may be straight when at rest. At least a portion of a longitudinal axis of the compliant mechanism may be straight when the compliant mechanism is at rest. At least a portion of a length of the compliant mechanism may be curved when at rest. At least a portion of a longitudinal axis of the compliant mechanism may be curved when the compliant mechanism is at rest. A length of the compliant mechanism may comprise a first portion and a second portion, wherein the first portion is straight and the second portion is curved. A longitudinal axis of the compliant mechanism may comprise a first portion and a second portion, wherein the first portion is straight and the second portion is curved. Both the first portion of the length or longitudinal axis of the compliant mechanism may be curved, wherein the first and second portions are curved in opposite directions.

[0078] The compliant mechanism may be shaped at rest such that the inherent restoring force of the compliant mechanism may be utilised to assist or support a desired articulation of a joint of the body of a wearer of the device in a direction opposite to a desired articulation of the joint assisted or supported by means of the at least one force element exerting a force on the compliant mechanism. For example, where the joint is a knee joint, the compliant mechanism may be curved at rest so as to conform to a leg of the body of the wearer when the knee joint is in a neutral position with the lower leg, below the knee, at approximately 90 degrees to the upper leg, above the knee. The desired articulation assisted or supported by means of the at least one force element exerting a force on the compliant mechanism may be extension of the knee joint. As such, the inherent restoring force of the compliant mechanism will assist or support flexion of the knee joint towards the neutral position.

[0079] The device may comprise at least one attachment for attaching the device to a part of the body of a wearer of the device. The at least one attachment may comprise two attachments. The device may comprise two of the actuator or support element. The two actuators or two support elements may extend between the two attachments for positioning on opposite sides of the joint. The compliant mechanism of the or each actuator or support element may extend between the two attachments. A first end of the compliant mechanism of the or each actuator or support element may be attached to one of the attachments. A second end of the compliant mechanism of the or each actuator or support element, opposite the first end, may be attached to the other attachment. The device may comprise at least one bracket, wherein the or each attachment is attached to the compliant mechanism of the or each actuator or support element via the at least one bracket. Alternatively, the or each attachment may be directly attached to the compliant mechanism of the or each actuator or support element.

[0080] The two attachments may comprise an upper attachment and a lower attachment. The or each attachment may comprise a U-shaped attachment. The upper attachment may comprise a convex U-shaped attachment. The lower attachment may comprise a concave U-shaped attachment. The terms ‘convex’ and ‘concave’ may refer to the geometry of the upper and lower attachments, respectively, when viewed from the front when the device is arranged in its normal orientation during normal use.

[0081] Where the or each compliant mechanism unit comprises two pairs of longitudinal compliant elements of equal length, wherein the length of the longitudinal compliant elements of one of the pairs of longitudinal compliant elements is different to the length of the longitudinal compliant elements of the other pair of longitudinal compliant elements, the upper attachment may be attached to a compliant element of the pair of shorter compliant elements of the respective compliant mechanism unit and the lower attachment may be attached to a compliant element of the pair of longer compliant elements of the respective compliant mechanism unit, or vice vera. In other examples, both the upper attachment and lower attachment may be attached to a compliant element of the pair of shorter compliant elements of the respective compliant mechanism unit, or both the upper attachment and lower attachment may be attached to a compliant element of the pair of longer compliant elements of the respective compliant mechanism unit.

[0082] The upper attachment may be configured for attaching the device to a part of the body of a wearer of the device above a corresponding joint of the body of the wearer. The lower attachment may be configured for attaching the device to the part of the body of the wearer of the device below the corresponding joint of the body of the wearer. The upper attachment may be configured to extend over the front of the part of the body of the wearer. The lower attachment may be configured to extend around the back of the part of the body of the wearer. In other examples, the upper attachment may be configured to extend around the back of the part of the body of the wearer and the lower attachment may be configured to extend over the front of the part of the body of the wearer. In other examples, both the upper and lower attachments may be configured to extend around the back of the part of the body of the wearer or both the upper and lower attachments may be configured to extend over the front of the part of the body of the wearer.

[0083] It will be appreciated that the terms ‘above’ and ‘below’ refer to positions relative to the joint when the human or animal is standing and the limb is at rest. For example, where the limb is an arm and the joint is an elbow, the arm will extend downwards from the shoulder towards the ground, such that ‘above’ the elbow refers to a position on the upper arm between the shoulder and elbow and ‘below’ the elbow refers to a position on the lower arm between the elbow and the hand.

[0084] It will be appreciated that the terms ‘upper’ and ‘lower’ refer to positions when the wearable exoskeleton device is arranged in its normal orientation during normal use.

[0085] The device may be configured such that the inherent restoring force of the compliant mechanism of the or each actuator or support element holds the device in place in use. In some examples, the device may comprise additional securing means, such as straps, to hold the device in place in use.

[0086] The part of the body of a wearer of the device as referred to herein may be a leg. The joint of the body of a wearer of the device as referred to herein may be a knee joint. In other examples, the device may be configured for use with any suitable joint, such as an elbow joint, ankle joint, wrist joint, or neck joint. The joint is preferably a synovial joint, also known as diarthrosis.

[0087] A fourth aspect provides a method of fabricating the wearable exoskeleton device of the first aspect, the actuator of the second aspect, or the support element of the third aspect.

[0088] The method may comprise forming the compliant mechanism using additive manufacturing. The method may comprise forming the compliant mechanism using fused deposition modelling (FDM). The method may comprise forming the compliant mechanism using FDM with an infill density in the range of 40-80%, 50-70%, or 55- 65%. The infill density may be 40%, 50%, 60%, 70%, or 80%, or within a range defined between any two of the preceding values. In other examples, an alternative additive manufacturing technique may be used, such as stereolithography. The use of additive manufacturing is particularly advantageous as it allows for customisation of the compliant mechanism for a particular wearer of the wearable exoskeleton device. In other examples, alternative manufacturing techniques may be used, such as moulding.

[0089] The method may comprise forming each of the two layers of the or each compliant mechanism unit, arranging the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of a respective compliant mechanism unit of the or each compliant mechanism unit, and securing the two layers of the or each compliant mechanism unit together to sandwich the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of the respective compliant mechanism unit.

[0090] Securing the two layers of the or each compliant mechanism unit together may comprise mechanically fastening the two layers together or heat sealing the two layers together.

[0091] The method preferably comprises forming each of the two layers of the or each compliant mechanism unit using additive manufacturing.

[0092] In some examples, the method may comprise: forming each of the two layers of the or each compliant mechanism unit; and passing the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of the or each compliant mechanism unit.

[0093] The method may comprise forming the two layers of the or each compliant mechanism unit integrally with each other. The two layers may be formed with one or more integral joints holding the two layers together. The one or more integral joints may separate the two layers to allow the or each lateral inflatable chamber and / or the or each central inflatable chamber to pass between the two layers. The method may comprise forming one or more spacers to separate the two layers. The spacers may be formed integrally with at least one of the two layers or may be formed separately.

[0094] The method may comprise passing the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of the or each compliant mechanism unit in a deflated state. The method may comprise securing the or each lateral inflatable chamber and / or the or each central inflatable chamber to a respective compliant mechanism unit of the or each compliant mechanism unit. The or each lateral inflatable chamber and / or the or each central inflatable chamber may be secured to the respective compliant mechanism unit by heat sealing, mechanical fastening, or other suitable means.

[0095] In some examples, the method may comprise: forming a first layer of the or each compliant mechanism; arranging the or each lateral inflatable chamber and / or the or each central inflatable chamber on top of the first layer of a respective compliant mechanism unit of the or each compliant mechanism unit; and forming a second layer of the or each compliant mechanism unit on top of the or each lateral inflatable chamber and / or the or each central inflatable chamber to sandwich the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of the respective compliant mechanism unit.

[0096] In some examples, the method may comprise: arranging the or each lateral inflatable chamber and / or the or each central inflatable chamber within a mould; injecting molten material into the mould to form the compliant structure mechanism; removing the or each lateral inflatable chamber and / or the or each central inflatable chamber and the complaint structure mechanism from the mould; and curing the compliant structure mechanism.

[0097] Any of the feature of any of the aspects described above may apply equally to any other of the aspects described above.

[0098] BRIEF DESCRIPTION OF THE DRAWINGS

[0099] Implementations will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0100] Figure la shows a side view of an actuator or support element for a wearable exoskeleton device; Figure lb shows an isometric front view of the actuator or support element of Figure la;

[0101] Figure 1c shows a compliant scissor mechanism of the actuator or support element of Figure la;

[0102] Figure Id shows the actuator or support element of Figure la with lateral inflatable chambers and central inflatable chambers inflated;

[0103] Figure le shows a close up of a compliant scissor mechanism units of the compliant scissor mechanism of the actuator or support element of Figure la;

[0104] Figure If shows the actuator or support element of Figure la positioned adjacent to a human knee joint 112;

[0105] Figure 2a shows a side view of a wearable exoskeleton device;

[0106] Figure 2b shows a front view of the wearable exoskeleton device of Figure 2a;

[0107] Figure 2c shows a side view of the wearable exoskeleton device of Figure 2a in use;

[0108] Figure 2d shows a front view of the wearable exoskeleton device of Figure 2a in use;

[0109] Figure 2e shows a front view of the wearable exoskeleton device of Figure 2a with a shear force applied to the device;

[0110] Figure 2f shows a front view of the wearable exoskeleton device of Figure 2a with a torque applied to the device;

[0111] Figure 2g shows a schematic representation of parts of the wearable exoskeleton device of Figure 2a;

[0112] Figure 3 shows a schematic representation of parts of a wearable exoskeleton wearable exoskeleton device according to another example;

[0113] Figure 4a shows an actuator or support element for a wearable exoskeleton device according to another example;

[0114] Figure 4b shows the actuator or support element of Figure 4a with central inflatable chambers inflated and first and second lateral inflatable chambers substantially deflated;

[0115] Figure 4c shows a close up of a compliant scissor mechanism unit of a compliant scissor mechanism of the actuator or support element of Figure 4a;

[0116] Figure 4d shows the actuator or support element of Figure 4a with central inflatable chambers and first lateral inflatable chambers inflated and second lateral inflatable chambers substantially deflated;

[0117] Figure 4e shows the actuator or support element of Figure 4a positioned adjacent to a human knee joint; Figure 5a shows an actuator or support element for a wearable exoskeleton device according to another example;

[0118] Figure 5b shows a side view of the actuator or support element of Figure 5a with a central inflatable chamber inflated;

[0119] Figure 5c shows an isometric view of the actuator or support element of Figure 5a with the central inflatable chamber inflated;

[0120] Figure 5d shows a schematic front view of a first layer of a compliant scissor mechanism of the actuator or support element of Figure 5a;

[0121] Figure 5e shows a schematic side view of the first layer of the compliant scissor mechanism of the actuator or support element of Figure 5a;

[0122] Figure 5f shows a schematic isometric view of the first layer of the compliant scissor mechanism of the actuator or support element of Figure 5a;

[0123] Figure 5g shows a schematic close-up front view of a compliant joint of a compliant scissor mechanism unit of the compliant scissor mechanism of the actuator or support element of Figure 5a.

[0124] Figure 5h shows a schematic close-up front view of a compliant joint of a compliant scissor mechanism unit of the compliant scissor mechanism of the actuator or support element of Figure 5a according to another example;

[0125] Figure 5i shows a schematic close-up front view of a compliant joint of a compliant scissor mechanism unit of the compliant scissor mechanism of the actuator or support element of Figure 5a according to another example;

[0126] Figure 6a shows a front view of a first example of a central inflatable chamber of the actuator or support element of Figure 5a;

[0127] Figure 6b shows a front view of a second example of the central inflatable chamber of the actuator or support element of Figure 5a;

[0128] Figure 6c shows a front view of a third example of the central inflatable chamber of the actuator or support element of Figure 5a;

[0129] Figure 6d shows a schematic representation of a main portion of the central inflatable chamber as shown in Figures 6a to 6c;

[0130] Figure 7a shows an actuator or support element for a wearable exoskeleton device according to another example;

[0131] Figure 7b shows the actuator or support element of Figure 7a with central inflatable chambers and first and second lateral inflatable chambers inflated;

[0132] Figure 7c shows a schematic front view of a compliant scissor mechanism of the actuator or support element of Figure 7a in a rest configuration and an extended configuration; Figure 8 illustrates a method of fabricating the actuator or support element of any of the above examples; and

[0133] Figures 9 to 12d show the results of experiments conducted on the actuator or support elements of Figures 5a and 7a.

[0134] DETAILED DESCRIPTION

[0135] Figure la shows a side view of an actuator 1 for a wearable exoskeleton device. In other examples, the actuator 1 may be a support element. The actuator 1 comprises a compliant scissor mechanism 11 and a plurality of force elements 12a-d, 13a-e. In this example, the plurality of force elements 12a-d, 13a-e are in the form of a plurality of inflatable chambers 12a-d, 13a-e. In other examples, alternative force elements, such as electrical or thermal force elements, may be provided in place of or in addition to the plurality of inflatable chambers 12a-d, 13a-e. Figure la shows the actuator in a rest configuration in which the plurality of inflatable chambers 12a-d, 13a-e are substantially deflated.

[0136] The compliant scissor mechanism 11 comprises a plurality of compliant scissor mechanism units 14a-e. In this example, the compliant scissor mechanism 11 comprises five compliant scissor mechanism units 14a-e. In other examples, the compliant scissor mechanism 11 may comprise more or fewer compliant scissor mechanism units. In some examples, the compliant scissor mechanism 11 may comprise a single compliant scissor mechanism unit.

[0137] Figure lb shows an isometric front view of the actuator 1 of Figure la. The compliant scissor mechanism 11 comprises a first layer 15 and a second layer 16. In this example, the first and second layers 15, 16 are substantially identical and each of the first layer 15 and the second layer 16 is formed as a single part. The first and second layers 15, 16 are fastened together using suitable mechanical fastenings. In other examples, the first and second layers 15, 16 may be attached together by alternative means, such as a suitable adhesive or bond.

[0138] In this example, each of the first layer 15 and the second layer 16 is formed of TPU using FDM additive manufacturing. In other examples, at least one of the first layer 15 and the second layer 16 may be formed using an alternative suitable compliant material and / or using an alternative manufacturing technique. In some examples, the first and second layers 15, 16 may be formed integrally with suitable integral joints holding the first and second layers 15, 16 together. The plurality of inflatable chambers are sandwiched between the first and second layers 15, 16, as described in further detail below with reference to the examples of Figures 5a to 6d.

[0139] Figure 1c shows the compliant scissor mechanism 11 of the actuator of Figure la in isolation from the plurality of inflatable chambers. Each compliant scissor mechanism unit 14a-e comprises four longitudinal compliant elements 17a-d and four compliant joints 18a-d. In other examples, one or more of the compliant scissor mechanism units 14a-e may comprise more or fewer longitudinal compliant elements and / or more or fewer compliant joints. The first layer of the compliant scissor mechanism 11 comprises a first longitudinal portion of each longitudinal compliant element 17a-d of each compliant scissor mechanism unit 14a-e and a first portion of each compliant joint 18a- d of each compliant mechanism unit 14a-e. The second layer of the compliant scissor mechanism 11 comprises a second longitudinal portion of each longitudinal compliant element 17a-d of each compliant scissor mechanism unit 14a-e and a second portion of each compliant joint 18a-d of each compliant mechanism unit 14a-e.

[0140] For each compliant mechanism unit 14a-e, the plurality of longitudinal compliant elements 17a-d are connected together by the plurality of compliant joints 18a-d. The plurality of longitudinal compliant elements 17a-d are arranged to define an enclosed space 19. For clarity, only the longitudinal compliant elements 17a-d, compliant joints 18a-d, and enclosed space 19 of one compliant scissor mechanism unit 14a are labelled in Figure 1c.

[0141] The compliant scissor mechanism 11 further comprises a first compliant joint 110 and a second compliant joint 111 connecting each compliant scissor mechanism unit 14a-e to an adjacent compliant scissor mechanism unit 14a-e. For clarity, only the first and second compliant joints 110, 111 connecting first and second adjacent compliant scissor mechanism units 14a, 14b are labelled in Figure 1c. In other examples, the compliant scissor mechanism may comprise a single compliant joint between adjacent compliant scissor mechanism units or more than two compliant joints between adjacent compliant scissor mechanism units. Figure 1c shows the compliant scissor mechanism 11 at rest, i.e., with no forces, other than gravity, acting on the compliant scissor mechanism 11. When at rest, the longitudinal axis ai of the compliant scissor mechanism 11 is curved. It will be appreciated that the slope of the curve of the longitudinal axis ai is merely illustrative. In other examples, the slope of the curve may be different, or the longitudinal axis may be straight, depending on the application of the actuator.

[0142] Referring back to Figure la, the plurality of inflatable chambers 12a-d, 13a-e comprises a lateral inflatable chamber 12a-d arranged between each compliant scissor mechanism unit 14a-e and an adjacent compliant scissor mechanism unit 14a-e. The lateral inflatable chambers 12a-d are in fluid communication with each other. The plurality of inflatable chambers 12a-d, 13a-e further comprises a central inflatable chamber 13a-e arranged within the enclosed space of each compliant scissor mechanism unit 14a-e. The central inflatable chambers 13a-e are in fluid communication with each other. Each of the lateral inflatable chambers 12a-d and each of the central inflatable chambers 13a- e are sandwiched between the first and second layers of the compliant scissor mechanism 11. In this example, each of the lateral inflatable chambers 12a-d and each of the central inflatable chambers 13a-e are formed from a TPU-coated nylon fabric.

[0143] Figure Id shows the actuator 1 of Figure la with the lateral inflatable chambers 12a-d and the central inflatable chambers 13a-e inflated. In this example, the lateral inflatable chambers 12a-d and the central inflatable chambers 13a-e take the form of pneumatic inflatable chambers and are inflated by pumping air into the inflatable chambers 12a-d, 13a-e. In other examples, alternative pneumatic or hydraulic chambers may be employed instead.

[0144] Inflating the lateral inflatable chambers 12a-d and the central inflatable chambers 13a- e causes the compliant scissor mechanism 11 to bend in a direction di towards a straight configuration and extend in a longitudinal direction d2. When the lateral inflatable chambers 12a-d are inflated, they exert a distributed actuation force on compliant scissor mechanism units 14a-e, causing the compliant scissor mechanism units 14a-e to pivot at the first and second compliant joints 18a-d, 19a-d connecting adjacent compliant scissor mechanism units 14a-e. This causes the compliant scissor mechanism 11 to bend in the direction di. When the central inflatable chambers 13a-e are inflated, they exert a distributed actuation force on the longitudinal compliant elements 17a-d of the respective compliant scissor mechanism units 14a-e, causing the longitudinal compliant elements 17a-d to pivot at the respective compliant joints 18a-d. This causes the longitudinal compliant elements 17a-d to move apart, thereby longitudinally extending the compliant scissor mechanism 11.

[0145] Figure le shows a close up of one of the compliant scissor mechanism units 14a of the compliant scissor mechanism 11 of the actuator of Figure la when the actuator is in the configuration shown in Figure Id. The four longitudinal compliant elements 17a-d form the sides of a nominal geometric kite, K, as indicated by the dotted line. A first pair of the longitudinal compliant elements 17a, 17c are of substantially equal length and a second pair of the longitudinal compliant elements 17b, 17d are of substantially equal length. Each longitudinal compliant element of the second pair of the longitudinal compliant elements 17b, 17d is longer than each longitudinal compliant element of the first pair of the longitudinal compliant elements 17a, 17c. As shown in Figures la and Id, the lateral inflatable chambers 12a-d are arranged between the longer longitudinal compliant elements 17b, 17d of the second pair of the longitudinal compliant elements 17b, 17d of respective adjacent compliant scissor mechanism units 14a-e.

[0146] Figure If shows the actuator 1 of Figure la positioned adjacent to a human knee joint 112.

[0147] Figure 2a shows a side view of a wearable exoskeleton device 2. Figure 2b shows a front view of the device 2 of Figure 2a. The device 2 comprises a first attachment 213, a second attachment 214, and two of the actuator la, lb of Figure la. The two actuators la, lb comprise a first actuator la and a second actuator lb. The first attachment 213 takes the form of an upper U-shaped attachment 213 comprising a first end 215 and a second end 216. The second attachment 214 takes the form of a lower U-shaped attachment 214 comprising a first end 217 and a second end 218.

[0148] As viewed from the front, i.e., as shown in Figure 2b, the upper U-shaped attachment 213 extends in a convex manner and the lower U-shaped attachment 214 extends in a concave manner. In other words, with reference to Figure 2b, the upper U-shaped attachment 213 extends out of the page, towards the viewer, and the lower U-shaped attachment 214 extends into the page, away from the viewer. It will be appreciated that the terms ‘upper’ and Tower’ in this context refer to positions when the wearable exoskeleton device 2 is arranged in its normal orientation during normal use, as shown in Figures 2a and 2b.

[0149] The device 2 further comprises four brackets 219a-d comprising a first bracket 219a, a second bracket 219b, a third bracket 219c, and a fourth bracket 219d. In this example, each of the four brackets 219a-d takes the form of an L-shaped bracket 219a-d. The upper and lower U-shaped attachments 213, 214 are attached to the compliant scissor mechanism 1 la, 1 lb of the first and second actuators la, lb via the four brackets 219a- d as described below. In other examples, the upper and lower U-shaped attachments 213, 214 may be directly mounted to the compliant scissor mechanism I la, 11b of the first and second actuators la, lb, or attached to the compliant scissor mechanism I la, 11b of the first and second actuators la, lb by other suitable means.

[0150] A first end 120a of the compliant scissor mechanism I la of the first actuator la is attached to the first end 215 of the upper U-shaped attachment 213 via the first U-shaped bracket 219a. A first end 120b of the compliant scissor mechanism 11b of the second actuator lb is attached to the second end 216 of the upper U-shaped attachment 213 via the second U-shaped bracket 219b. A second end 121a of the compliant scissor mechanism I la of the first actuator la is attached to the first end 217 of the lower U- shaped attachment 214 via the third U-shaped bracket 219c. A second end 121b of the compliant scissor mechanism 11b of the second actuator lb is attached to the second end 218 of the lower U-shaped attachment 214 via the fourth U-shaped bracket 219d.

[0151] The brackets 219a-d are attached to the upper and lower U-shaped attachments 213, 214 and the first and second actuators la, lb by suitable mechanical fastenings. In other examples, alternative means for attaching the brackets 219a-d to the upper and lower U-shaped attachments 213, 214 and the first and second actuators la, lb may be provided, such as a suitable adhesive or bond. In other examples, the upper and lower U-shaped attachments 213, 214 may be formed integrally with the compliant scissor mechanism I la, 11b of the first and second actuators la, lb.

[0152] As shown in Figure 2a, the first U-shaped bracket 219a is attached to an upper longitudinal compliant element 17a of the first pair of shorter longitudinal compliant elements of an upper compliant scissor mechanism unit of the compliant scissor mechanism I la of the first actuator la. The third U-shaped bracket 219c is attached to a lower longitudinal compliant element 17d of the second pair of longer longitudinal compliant elements of a lower compliant scissor mechanism unit of the compliant scissor mechanism 1 la of the first actuator la. The second and fourth L-shaped brackets are attached to the compliant scissor structure of the second actuator in the same manner.

[0153] In other examples, the first L-shaped bracket 219a may be attached to an upper longitudinal compliant element 17b of the second pair of longer longitudinal compliant elements of an upper compliant scissor mechanism unit of the compliant scissor mechanism I la of the first actuator la, and the third L-shaped bracket 219c may be attached to a lower longitudinal compliant element 17c of the first pair of shorter longitudinal compliant elements of a lower compliant scissor mechanism unit of the compliant scissor mechanism I la of the first actuator la. In other examples, both the first and third L-shaped brackets 219a, 219c may be attached to respective upper and lower longitudinal compliant elements of the second pair of longer longitudinal compliant elements of a respective upper and lower compliant scissor mechanism unit of the compliant scissor mechanism I la of the first actuator la, or both the first and third L-shaped brackets 219a, 219c may be attached to respective upper and lower longitudinal compliant elements of the first pair of shorter longitudinal compliant elements of a respective upper and lower compliant scissor mechanism unit of the compliant scissor mechanism I la of the first actuator la. The second and fourth L- shaped brackets may be attached to the compliant scissor structure of the second actuator in the same manner, or in any other manner as described above.

[0154] Figure 2c shows a side view of the wearable exoskeleton device 2 of Figure 2a in use. Figure 2d shows a front view of the wearable exoskeleton device 2 of Figure 2a in use. In this example, the device 2 is configured to assist a desired articulation of a human knee joint 212 of the body of a wearer of the device 2. The lateral inflatable chambers and the central inflatable chambers of each of the first and second actuators la, lb are configured to exert an actuation force on the respective compliant scissor mechanism, as described above with reference to Figures la and Id, to assist a desired articulation of the knee joint 212.

[0155] The compliant scissor mechanisms are configured to resist articulations that are outside the desired articulation and substantially freely allow the desired articulation. This is achieved through the relative stiffness of the compliant scissor mechanisms I la, 11b with respect to forces to affect the desired articulation and forces to affect articulations outside the desired articulation, as described herein. The relative stiffness may be achieved by making some parts of the compliant scissor mechanisms thicker than other parts of the compliant scissor mechanisms in a given direction of measurement.

[0156] The first and second actuators la, lb extend between the upper and lower attachments 213, 214 for positioning on opposite sides of the knee joint 212. The upper and lower attachments 213, 214 are configured for attaching the device 2 to a leg 220 of the body of a wearer of the device 2 above and below the corresponding knee joint, respectively. The upper attachment 213 is configured to extend over the front of an upper leg 221 of the body of the wearer and the lower attachment is 214 is configured to extend around the back of a lower leg 222 of the body of the wearer. In this example, the inherent restoring force of the compliant mechanism of the first and second actuators holds the device 2 in place in use. In other examples, the device 2 may comprise additional securing means for holding the device 2 in place.

[0157] Figure 2e shows a front view of the device 2 of Figure 2a with a shear force applied between the upper and lower U-shaped attachments 213, 214, as indicated by the arrows, Fs. Figure 2f shows a front view of the device 2 of Figure 2a with a torque applied about a longitudinal axis a2 of the device 2, as indicated by the arrows, FT.

[0158] The compliant scissor mechanism 1 la, 1 lb of each of the first and second actuators la, lb is compliant in three dimensions. Each compliant scissor mechanism I la, 11b is compliant within a normal plane of motion of the knee joint 212, i.e., within the plane of the page of Figure 2c. As demonstrated in Figures 2e and 2f, each compliant scissor mechanism 1 la, 1 lb is further compliant with out of normal plane of motion of the knee joint 212 with respect to both shear and torsional forces.

[0159] Figure 2g shows a schematic representation of parts of the device of Figure 2a. The device further comprises a control system 223 to control the pressure of air within the lateral inflatable chambers 12a-d and the central inflatable chambers 13a-e of each of the first and second actuators la, lb to control the force exerted on the respective compliant scissor mechanisms of the first and second actuators la, lb. Figure 2g shows the first and second actuators la, lb and the control system 223 in isolation from the rest of the wearable exoskeleton device. In Figures 2a-f, the control system 223 is not shown.

[0160] The control system 223 comprises a pump 224, a plurality of valves 225a-d, a controller 226, and a sensor array 227. The controller 226 is in electronic communication with the pump 224, each valve of the plurality of valves 225a-d, and the sensor array 227, as indicated by the dashed lines in Figure 2g. The plurality of valves 225a-d comprises a first valve 225a, a second valve 225b, a third valve 225c, and a fourth valve 225d. The pump 224 is in fluid communication with the central inflatable chambers 13a-e of the first actuator la via the first valve 225a, the lateral inflatable chambers 12a-d of the first actuator la via the second valve 225b, the central inflatable chambers 13a-e of the second actuator lb via the third valve 225c, and the lateral inflatable chambers 12a-d of the second actuator lb via the fourth valve 225d, as indicated by the solid lines in Figure 2g.

[0161] Each of the plurality of valves 225a-d is configured to adopt a closed position in which air is substantially prevented from flowing through the valve, a first open position in which air is permitted to flow through the valve from the pump to the respective lateral inflatable chambers or central inflatable chambers, and a second open position in which air is permitted to flow through the valve from the respective lateral inflatable chambers or central inflatable chambers to the atmosphere.

[0162] To control the air pressure within the central inflatable chambers 13a-e of the first actuator la, the controller 226 is configured to provide an input to the pump 224 to generate a flow of air and provide an input to the first valve 225a to adopt the first open position, thereby allowing air to flow into the central inflatable chambers 13a-e. After the air pressure within the central inflatable chambers 13a-e has reached a desired value, the controller 226 is configured to provide an input to the pump 224 to stop generating a flow of air.

[0163] The control system 223 comprises means for determining when the air pressure within the central inflatable chambers 13a-e has reached the desired value. In some examples, the control system 223 may comprise one or more pressure sensors configured to determine the air pressure within the central inflatable chambers 13a-e and output one or more signals indicative of the air pressure within the central inflatable chambers 13a- e to the controller 226. The controller 226 may be configured to provide an input to the pump 224 to stop generating a flow of air in response to receiving one or more signals from the one or more pressure sensors indicative of the air pressure within the central inflatable chambers reaching the desired value. In other examples, the control system

[0164] 223 may be configured to determine when the air pressure within the central inflatable chambers has reached the desired value by means of a known relationship between operation of the pump 224 and the first valve 225a.

[0165] In some examples, the control system 223 may comprise one or more force sensors configured to determine a magnitude of one or more forces exerted on the respective compliant scissor mechanism and output one or more signals indicative of a magnitude of one or more forces exerted on the respective compliant scissor mechanism to the controller 226. The controller 226 may be configured to provide an input to the pump

[0166] 224 to stop generating a flow of air in response to receiving one or more signals from the one or more force sensors indicative of a target force being exerted on the respective compliant scissor mechanism by the central inflatable chambers.

[0167] If it is desired to maintain the air pressure within the central inflatable chambers 13a-e at the desired value, the controller 226 is configured to provide an input to the first valve 225a to adopt the closed position. If it is desired to reduce the pressure within the central inflatable chambers 13a-e, the controller 226 is configured to provide an input to the first valve 225a to adopt the second open position.

[0168] The control system 223 is configured to control the pump 224 and the second valve 225b, the third valve 225c, and the fourth valve 225d in the same manner described in the preceding paragraph to control the air pressure within the lateral inflatable chambers 12a-d of the first actuator la, the central inflatable chambers 13a-e of the second actuator lb, and the lateral inflatable chambers 12a-d of the second actuator lb, respectively. In this way, the air pressure within the central inflatable chambers 13a-e of the first actuator la, the lateral inflatable chambers 12a-d of the first actuator la, the central inflatable chambers 13a-e of the second actuator lb, and the lateral inflatable chambers 12a-d of the second actuator lb can be controlled independently.

[0169] The sensor array 227 is configured to measure movement of a wearer of the device and generate signals indicative of movement of the wearer. The sensor array 227 may comprise any suitable arrangement of sensors configured to measure movement, such as one or more accelerometers, gyroscopes, etc. The controller 226 is configured to receive the signals from the sensor array 227 and provide inputs to the pump 224 and the plurality of valves 225a-d in dependence on the signals to control the pressure of air within the lateral inflatable chambers 12a-d and the central inflatable chambers 13a-e of each of the first and second actuators la, lb, thereby controlling the force exerted on the respective compliant scissor mechanisms of the first and second actuators la, lb, as described above.

[0170] For example, the sensor array 227 may generate signals indicating that a wearer of the device is attempting an extension of the knee joint. The controller 226 may then provide inputs to the pump 224 and the plurality of valves 225a-d in dependence on the signals to control the pressure of air within the lateral inflatable chambers 12a-d and the central inflatable chambers 13a-e of each of the first and second actuators la, lb, thereby controlling the force exerted on the respective compliant scissor mechanisms of the first and second actuators la, lb, to assist the extension of the knee joint.

[0171] In other examples, the control system 223 may comprise a memory configured to store a set of instructions for operation of the device. The memory may be provided in addition to or in place of the sensor array 227. The set of instructions may comprise predetermined control logic for providing inputs to the pump 224 and the plurality of valves 225a-d.

[0172] In other examples, the pump 224 may be replaced by a source of compressed fluid, such as a compressed air tank or reservoir, with the controller 226 being configured to control the plurality of valves 225a-d to control a release of fluid from the source of compressed fluid to control the pressure of air within the inflatable chambers 12a-d, 13a-e as described above.

[0173] It will be appreciated that the control system 223 as described above is merely illustrative and that in other examples, the device may comprise other suitable control means for controlling the air pressure within the lateral inflatable chambers and the central inflatable chambers of the respective first and second actuators la, lb, thereby controlling the device to assist a desired articulation of a joint of the body of a wearer of the device. For examples, where each lateral inflatable chamber and / or each central inflatable chamber of the first actuator and / or second actuator are fluidly separate, the control system may comprise a valve for each individual lateral inflatable chamber and / or each central inflatable chamber. Each valve may be individually controllable to control the air pressure within each individual lateral inflatable chamber and / or each central inflatable chamber independently.

[0174] Figure 3 shows a schematic representation of parts of a wearable exoskeleton device 3 according to another example. The device 3 is substantially the same as the device of Figure 2a except that the first and second actuators are instead support elements la, lb and the control system is not present. The lateral inflatable chambers and the central inflatable chambers of each of the first and second support elements la, lb are configured to exert a support force on the respective compliant scissor mechanism 11 to support a desired articulation of a knee joint of the body of a wearer of the device 3. In use, the wearer of the device 3 may exert a force on the compliant scissor mechanism 11 of the support elements la, lb when affecting a desired articulation of the knee joint. When inflated, the lateral inflatable chambers and / or the central inflatable chambers of each of the first and second support elements la, lb will exert a support force on the respective compliant scissor mechanism 11 in reaction to the force exerted by the wearer of the device 3 to support the desired articulation. This effect will be provided at least in part by air within the lateral inflatable chambers moving between the lateral inflatable chambers and / or air within the central inflatable chambers moving between the central inflatable chambers.

[0175] The device 3 comprises control means to control the pressure of air within the lateral inflatable chambers 12a-d and the central inflatable chambers 13a-e of each of the first and second support elements la, lb in the form of a plurality of manually operated valves 328a-d. The plurality of manually operated valves 328a-d comprises a first manually operated valve 328a, a second manually operated valve 328b, a third manually operated valve 328c, and a fourth manually operated valve 328d. The central inflatable chambers 13a-e of the first support element la are in fluid communication with the first manually operated valve 328a. The lateral inflatable chambers 12a-d of the first support element la are in fluid communication with the second manually operated valve 328b. The central inflatable chambers 13a-e of the second support element lb are in fluid communication with the third manually operated valve 328c. The lateral inflatable chambers 12a-d of the second support element lb are in fluid communication with the fourth manually operated valve 328d.

[0176] Each of the manually operated valves 328a-d is operable in a first configuration in which air is permitted to flow through the valve into the respective lateral inflatable chambers or central inflatable chambers and air is substantially prevented from flowing out of the respective lateral inflatable chambers or central inflatable chambers through the valve. Each of the manually operated valves 328a-d is also operable in a second configuration in which air is permitted to flow out of the respective inflatable chamber through the valve. Each of the manually operated valves 328a-d is manually reconfigurable between the first and second configurations.

[0177] In use, when it is desired to increase the air pressure within the central inflatable chambers 13a-e of the first support element la, a user can configure the first manually operated valve 328a in the first configuration and provide air to the central inflatable chambers 13a-e, for example by blowing into the first manually operated valve 328a or by attaching a pump to the first manually operated valve 328a. When it is desired to decrease the air pressure within the central inflatable chambers 13a-e, the user can reconfigure the first manually operated valve 328a in the second configuration to allow air to flow out of the central inflatable chambers 13a-e. In this way, the air pressure within the central inflatable chambers 13a-e, and therefore the force exerted on the respective compliant mechanism I la by the central inflatable chambers 13a-e can be controlled. The second manually operated valve 328b, the third manually operated valve 328c, and the fourth manually operated valve 328d are operable in the same manner to control the air pressure within the lateral inflatable chambers 12a-d of the first support element la, the central inflatable chambers 13a-e of the second support element lb, and the lateral inflatable chambers 12a-d of the second support element lb, respectively.

[0178] Other examples may comprise a combination of the features of the device of Figure 2a and the device of Figure 3. For example, the device of Figure 2a may comprise the first and third manually operated valves of the device of Figure 3 in place of the first and third valves or the second fourth manually operated valves of the device of Figure 3 in place of the second and fourth valves. Figure 4a shows an actuator 4 for a wearable exoskeleton device according to another example. In other examples, the actuator 4 may be a support element. The actuator 4 has features in common with the actuator of Figure la. Features of the actuator 4 in common with the actuator of Figure la are indicated by like reference numerals preceded by ‘4’ in Figure 4a in place of ‘ 1 ’ in Figure la. The actuator 4 may comprise any of the features of the actuator of Figure la.

[0179] In this example, the plurality of inflatable chambers 42Aa-d, 42Ba-d, 43a-e comprises a first lateral inflatable chamber 42Aa-d arranged between each compliant scissor mechanism unit 44a-e and an adjacent compliant scissor mechanism unit 44a-e, a second lateral inflatable chamber 42Ba-d arranged between each compliant scissor mechanism unit 44a-e and an adjacent compliant scissor mechanism unit 44a-e, and a central inflatable chamber 43a-e arranged within the enclosed space of each compliant scissor mechanism unit 44a-e. The first and second lateral inflatable chambers 42Aa-d, 42Ba- d are arranged on opposite sides of the first and second compliant joints 410a-d, 411a- d connecting each compliant scissor mechanism unit 44a-e to an adjacent compliant scissor mechanism unit 44a-e. The first lateral inflatable chambers 42Aa-d are in fluid communication with each other, the second lateral inflatable chambers 42Ba-d are in fluid communication with each other, and the central inflatable chambers 43a-e are in fluid communication with each other.

[0180] Figure 4a shows the compliant scissor mechanism 41 at rest, i.e., with the plurality of inflatable chambers substantially deflated. When at rest, the longitudinal axis a.3 of the compliant scissor mechanism 41 is straight.

[0181] Figure 4b shows the actuator 4 of Figure 4a with the central inflatable chambers 43a-e inflated and the first and second lateral inflatable chambers 42Aa-d, 42Ba-d substantially deflated. When the central inflatable chambers 43a-e are inflated, they exert a distributed actuation force on the longitudinal compliant elements of the respective compliant scissor mechanism units 44a-e, causing the longitudinal compliant elements to pivot at the respective compliant joints (see Figure 4c). This causes the longitudinal compliant elements to move apart, thereby causing the compliant scissor mechanism 41 to extend in a longitudinal direction ds. Figure 4c shows a close up of one of the compliant scissor mechanism units 44a of the compliant scissor mechanism 41 of the actuator 4 of Figure 4a when the actuator 4 is in the configuration shown in Figure 4b. In this example, the four longitudinal compliant elements 47a-d of the compliant scissor mechanism unit 44a are of equal length. The four longitudinal compliant elements 47a-d form the sides of a nominal geometric rhombus, R, as indicated by the dotted line. As shown in Figures 4a and 4b, the first and second lateral inflatable chambers 42Aa-d, 42Ba-d are arranged between longitudinal compliant elements 47a-d of respective adjacent compliant scissor mechanism units 44a-e.

[0182] In some examples, the compliant mechanism may comprise a combination of the any number of each of the compliant scissor mechanism units of Figure le and the compliant scissor mechanism units of Figure 4c. The geometry of the compliant scissor mechanism units may be selected depending on a particular application.

[0183] Figure 4d shows the actuator 4 of Figure 4a with the central inflatable chambers 43a-e and the first lateral inflatable chambers 42Aa-d inflated, and the second lateral inflatable chambers 42Ba-d substantially deflated. For clarity, in Figure 4d only the longitudinal compliant elements 47a-d and compliant joints 48a-d of one compliant scissor mechanism unit 44a and only the first and second compliant joints 410, 411 connecting first and second adjacent compliant scissor mechanism units 44a, 44b are labelled.

[0184] When the first lateral inflatable chambers 42Aa-d are inflated, they exert a distributed actuation force on the respective compliant scissor mechanism units, causing the compliant scissor mechanism units to pivot at the first and second compliant joints 410, 411 connecting adjacent compliant scissor mechanism units. The first compliant joints 410 connecting adjacent compliant scissor mechanism units extend and the second compliant joints 411 connecting adjacent compliant scissor mechanism units compress. This causes the compliant scissor mechanism 41 to bend in a direction d4.

[0185] When the central inflatable chambers 43a-e and the second lateral inflatable chambers 42Ba-d inflated, and the first lateral inflatable chambers 42Aa-d are substantially deflated, the second lateral inflatable chambers 42Ba-d exert a distributed actuation force on compliant scissor mechanism units, causing the compliant scissor mechanism units to pivot at the first and second compliant joints connecting adjacent compliant scissor mechanism units. The second compliant joints connecting adjacent compliant scissor mechanism units extend and the first compliant joints connecting adjacent compliant scissor mechanism units compress. This causes the compliant scissor mechanism 41 to bend in the opposite direction to the direction d4.

[0186] Figure 4e shows the actuator 4 of Figure 4a, in the configuration shown in Figure 4d, positioned adjacent to a human knee joint 412.

[0187] In some examples, the actuator 4 of Figure 4a may replace each of the first and second actuators of the device of Figure 2a. In such examples, the control system of the device, as shown in Figure 2g, may comprise a valve for each of: the first lateral inflatable chambers of the first actuator, the central inflatable chambers of the first actuator, the second lateral inflatable chambers of the first actuator, the first lateral inflatable chambers of the second actuator, the central inflatable chambers of the second actuator, and the second lateral inflatable chambers of the second actuator. The control system may operate in the same manner as described above with reference to Figure 2g.

[0188] In some examples, where the actuator 4 is a support element 4, the support element 4 may replace each of the first and second support elements of the device of Figure 3. In such examples, the device may comprise a manually operated valve for each of: the first lateral inflatable chambers of the first actuator, the central inflatable chambers of the first actuator, the second lateral inflatable chambers of the first actuator, the first lateral inflatable chambers of the second actuator, the central inflatable chambers of the second actuator, and the second lateral inflatable chambers of the second actuator. The manually operated valves may operate in the same manner as described above with reference to Figure 3.

[0189] Figure 5a shows an actuator 5 for a wearable exoskeleton device according to another example. In other examples, the actuator 5 may be a support element. The actuator 5 has features in common with the actuator of Figure 4a. Features of the actuator 5 in common with the actuator of Figure 4a are indicated by like reference numerals preceded by ‘5’ in Figure 5a in place of ‘4’ in Figure 4a. The actuator 5 may comprise any of the features of the actuator of Figure 4a. The actuator 5 is substantially the same as the actuator of Figure 4a, except that the compliant scissor mechanism 51 of the actuator 5 comprises a single compliant scissor mechanism unit 54 and the actuator 5 does not comprise lateral inflatable chambers. Figure 5a shows the compliant scissor mechanism 51 at rest, i.e., with the central inflatable chamber 53 substantially deflated. Figure 5b shows a side view of the actuator 5 with the central inflatable chamber 53 inflated. Figure 5c shows an isometric view of the actuator 5 with the central inflatable chamber 53 inflated.

[0190] Figure 5d shows a schematic front view of the first layer 55 of the compliant scissor mechanism of Figure 5a. The first longitudinal portion of each longitudinal compliant element of the compliant scissor mechanism unit is indicated with the reference numeral of the respective longitudinal compliant element followed by ‘i1. The first portion of each compliant joint of the compliant scissor mechanism unit is indicated with the reference numeral of the respective compliant joint followed by ‘i1.

[0191] Figure 5e shows a schematic side view of the first layer 55 of the compliant scissor mechanism. Figure 5f shows a schematic isometric view of the first layer 55 of the compliant scissor mechanism unit. In each of Figures 5e to 5f, the first layer 55 of the compliant scissor mechanism unit is shown in a rest configuration, i.e., with no external forces acting on the first layer 55 of the compliant scissor mechanism unit.

[0192] In Figures 5d and 5e, x-, y-, and z-axes are defined. The y-axis corresponds to the longitudinal direction in which the compliant scissor mechanism unit extends when the central inflatable chamber is inflated. Referring to Figure 5d, the first longitudinal portion 57ai-di of each longitudinal compliant element has a width Wb as measured in the direction of the y-axis and the first portion 58ai-di of each compliant joint has a width Wj as measured in the direction of the y-axis. Referring to Figure 5e, the first longitudinal portion 57ai-di of each longitudinal compliant element has a length lb as measured in the direction of the x-axis, the first longitudinal portion 57ai-di of each longitudinal compliant element has a height hb as measured in the direction of the z- axis, the first portion 58ai-di of each compliant joint has length lj as measured in the direction of the x-axis, and the first portion 58ai-di of each compliant joint has height hj as measured in the direction of the z-axis. It will be appreciated that because the second layer 56 of the compliant scissor mechanism unit of Figure 5a is substantially identical to the first layer 55, the second longitudinal portion of each longitudinal compliant element and the second portion of each compliant joint will have dimensions substantially identical to those of the first longitudinal portion of each longitudinal compliant element and the first portion of each compliant joint, respectively, as described in the preceding paragraph.

[0193] Figure 5g shows a schematic close-up front view of one of the compliant joints 58bi of the compliant scissor mechanism unit of Figure 5a. In Figure 5g, x-, y-, and z-axes are defined as shown in Figures 5d and 5e. In the example of Figure 5g, the compliant joint 58bi comprises a rectangular cross-section as viewed in the direction of the z-axis.

[0194] Figure 5h shows a schematic close-up front view of one of the compliant joints 58bi of the compliant scissor mechanism unit of Figure 5a according to another example. In Figure 5h, x-, y-, and z-axes are defined as shown in Figures 5d to 5e. In the example of Figure 5h, the compliant joint 58bi comprises a single-curved cross-section, as viewed in the direction of the z-axis, comprising a curve 529.

[0195] Figure 5i shows a schematic close-up front view of one of the compliant joints 58bi of the compliant scissor mechanism unit of Figure 5a according to another example. In Figure 5i, x-, y-, and z-axes are defined as shown in Figures 5d to 5e. In the example of Figure 5i, the compliant joint 58bi comprises a double-curved cross-section, as viewed in the direction of the z-axis, comprising a first curve 529 and a second curve 530. The second curve 530 is inverted with respect to the first curve 529.

[0196] At least one or all of the compliant joints of the compliant scissor mechanism unit of Figure 5a may comprise the cross-section of Figure 5g, Figure 5h, or Figure 5i. At least one or all of the compliant joints of any of the compliant scissor mechanism units of any of the other examples described above may comprise the cross-section of Figure 5g, Figure 5h, or Figure 5i.

[0197] Figures 6a to 6c each show a front view of a different example of the central inflatable chamber 53 of the actuator of Figure 5a. The central inflatable chamber 53 as shown is substantially deflated and laid flat. The central inflatable chamber 53 comprises a main portion 629 and an intermediate portion 630 in fluid communication with the main portion 629. The central inflatable chamber 53 further comprises an inlet port 631, in fluid communication with the intermediate portion 630, to enable air to enter the central inflatable chamber 53. In other examples, the intermediate portion 630 may not be present and the inlet port 631 may be arranged in direct fluid communication with the main portion 629.

[0198] In each of Figures 6a to 6c, x-, y-, and z-axes are defined as shown in Figures 5d and 5e. In each of Figures 6a to 6c, the main portion 629 of the central inflatable chamber 53 comprises a different maximum width wcas measured in the direction of the y-axis when in a flat configuration as shown. In the example of Figure 6a, the maximum wcis equal to 31mm. In the example of Figure 6b, the maximum wcis equal to 59mm. In the example of Figure 6c, the maximum width wcis equal to 81mm. Each example of the central inflatable chamber 53 has a different maximum volume when inflated, proportional to the maximum width wc, corresponding to a different maximum longitudinal extension of the compliant scissor mechanism unit. It will be appreciated that different maximum longitudinal extensions of the compliant scissor mechanism unit may be required depending on the application.

[0199] The main portion 629 of the central inflatable chamber 53 in the configuration shown in each of Figures 6a to 6c comprises four major edges 632a-d and two minor edges 633a-b forming the sides of a nominal hexagon (see Figure 6a). Each of the two minor edges 633a-b extend in parallel in the direction of the x-axis. The four major edges 632a-d extend between the two minor edges 633a-b. The length of each of the four major edges 632a-d is equal to the length of each longitudinal compliant element of the compliant mechanism unit as described above with reference to Figure 5e. The main portion 629 of the central inflatable chamber 53 comprises a tab 634a-d attached to and extending along the length of each of the four major edges 632a-d (see Figure 6a). When assembled, each tab 634a-d is sandwiched between the first and second longitudinal portions of a respective longitudinal compliant element of the compliant scissor mechanism unit. The first and second longitudinal portions are fastened together using one or more suitable mechanical fastenings extending through the first and second longitudinal portions and the tab sandwiched between the respective first and second longitudinal portions. Each of the central inflatable chambers of the example actuators and support elements described with reference to the accompanying figures comprise the same configuration of tabs as shown in Figures 6a to 6c, the tabs being sandwiched between first and second longitudinal portions of respective longitudinal compliant elements in the same manner as described in the preceding paragraph. Although not shown, the lateral inflatable chambers of the examples of the applicable example actuators and support elements described with reference to the accompanying figures also comprise tabs sandwiched between first and second longitudinal portions of respective longitudinal compliant elements in the same manner as described in the preceding paragraph.

[0200] Figure 6d shows a schematic representation of the main portion 629 of the central inflatable chamber 53 as shown in Figures 6a to 6c. The tabs are not shown in Figure 6d. The central inflatable chamber 53 may be fabricated by forming two hexagonal pieces of material and heat sealing the two hexagonal pieces of material together to form a volume between the two hexagonal pieces of material. Figure 6d illustrates the geometry of one of the hexagonal pieces of material.

[0201] The dimension lb as shown in Figure 6d corresponds to the length of the major edges of the main portion 629 of the central inflatable chamber 53, as described above, which corresponds to the length of the longitudinal compliant elements of the respective compliant scissor mechanism unit. The dimension lj as shown in Figure 6d corresponds to the length of the compliant joints as described above with reference to Figures 5d and 5e. The dimensions lp,h and lp>vas shown in Figure 6d are calculated using the following equations: where dmax is the desired the maximum longitudinal extension of the respective compliant scissor mechanism unit. The value of dmax for the central inflatable chambers in Figure 6a, 6b and 6c are 20mm, 40mm and 60mm, respectively.

[0202] Figure 7a shows an actuator 7 for a wearable exoskeleton device according to another example. In other examples, the actuator 7 may be a support element. The actuator 7 has features in common with the actuator of Figure 4a. Features of the actuator 7 in common with the actuator of Figure 4a are indicated by like reference numerals preceded by ‘7’ in Figure 7a in place of ‘4’ in Figure 4a. The actuator 7 may comprise any of the features of the actuator of Figure 4a.

[0203] The actuator 7 is substantially the same as the actuator of Figure 4a, except that the compliant scissor mechanism 71 of the actuator 7 comprises two compliant mechanism units. Figure 7a shows the compliant scissor mechanism 71 at rest, i.e., with the central inflatable chambers 73a, 73b and the first and second lateral inflatable chambers 72A, 72B substantially deflated. Figure 7b shows the actuator 7 with the central inflatable chambers 73a, 73b and the first and second lateral inflatable chambers 72A, 72B inflated.

[0204] Figure 7c shows a schematic front view of the compliant scissor mechanism 71 of the actuator of Figure 7a in a rest configuration (left-hand side of Figure 7c) and an extended configuration (right-hand side of Figure 7c). In Figure 7c, x-, y-, and z-axes are defined as shown in Figures 5d and 5e. The width, length, and height of the longitudinal compliant elements and the compliant joints of each compliant scissor mechanism unit of the compliant scissor mechanism 71 are as defined with respect to the compliant scissor mechanism of Figures 5d and 5e. The first and second compliant joints connecting the compliant scissor mechanism units have the same width, length, and height as defined with respect to the compliant joints connecting the longitudinal compliant elements of Figures 5d and 5e. As such, the total width as measured in the direction of the y-axis of the compliant scissor mechanism 71 in the rest configuration shown in Figure 7c is equal to 4wb+31j.

[0205] The above description refers to a ‘rest configuration’ shown as a contracted configuration in the accompanying drawings, relative to the ‘extended configuration’ described above. In any of the described examples, the compliant mechanism may instead adopt an extended configuration when at rest, i.e., with no forces, other than gravity, acting on the compliant mechanism, and adopt a contracted configuration when the one or more force elements are operated to exert a force on the compliant mechanism.

[0206] It will be appreciated that the actuators, support elements, and wearable exoskeleton devices described above are merely illustrative and that any variations of the actuators, support elements, and wearable exoskeleton devices are possible within the scope of the appended claims. Any of the actuators or support elements described above may comprise any of the features of any other of the actuators or support elements described above. Any of the wearable exoskeleton devices described above may comprise any of the features of any other of the wearable exoskeleton devices described above.

[0207] It will be appreciated that any dimensions or other values shown in any of the figures described above are merely exemplary and that in other examples any suitable dimensions or other values may be applied.

[0208] Figure 8 illustrates a method 8 of fabricating the actuator of any of the examples described above. The method 8 comprises forming 801 each of the two layers of the or each compliant mechanism unit from TPU using FDM additive manufacturing. The method 8 then comprises arranging 802 the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of a respective compliant mechanism unit of the or each compliant mechanism unit, such that the tabs of the inflatable chambers align with the longitudinal compliant elements of the respective compliant mechanism unit. Finally, the method comprises securing 803 the two layers of the or each compliant mechanism unit together to sandwich the tabs of the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of the respective compliant mechanism unit.

[0209] It will be appreciated that other examples of methods of fabricating any of the actuators described herein are possible within the scope of the appended claims.

[0210] Experimental validation and results

[0211] The following describes experiments and results conducted on the actuators of Figures 5a and 7a as described above. In the experiments, the compliant scissor mechanisms of the actuators were formed of TPU using FDM additive manufacturing with a 60% infill density. In each of the experiments, the values of Wb, lb, and lj, as defined above with reference to Figures 5d and 5e, were set at 5mm, 50mm, and 4mm, respectively. The values of hb and Wj, as defined above with reference to Figures 5d and 5e, was varied for different experiments. The value of hj, as defined above with reference to Figures 5d and 5e, was set at 2mm less than hb.

[0212] Force-strain evaluation In a first experiment, a force-strain evaluation was conducted on a single layer of the compliant scissor mechanism of the actuator of Figure 5a in isolation from the central inflatable chamber. The compliant scissor mechanism was extended longitudinally, i.e., extended in the direction of the y-axis as shown in Figure 5d, from the rest configuration as shown in Figure 5d with respect to the first layer of the compliant scissor mechanism. The restoring force of the compliant scissor mechanism, i.e., the force exerted by the compliant scissor mechanism in the direction opposite the direction of extension, was measured during extension. This was repeated for different examples of the compliant scissor mechanism of the actuator of Figure 5a.

[0213] The different examples of the compliant scissor mechanism of the actuator of Figure 5a included a first, second, third, fourth, fifth, and sixth example. For each example, the value of hb was set at 6mm. In the first example, each of the compliant joints comprised the rectangular cross-section shown in Figure 5g and the value of Wj was set at 4mm. In the second example, each of the compliant joints comprised the single-curved crosssection shown in Figure 5h and the value of Wj was set at 4mm. In the third example, each of the compliant joints comprised the double-curved cross-section shown in Figure 5i and the value of Wj was set at 4mm. In the fourth example, each of the compliant joints comprised the rectangular cross-section shown in Figure 5g and the value of Wj was set at 2mm. In the fifth example, each of the compliant joints comprised the singlecurved cross-section shown in Figure 5h and the value of Wj was set at 2mm. In the sixth example, each of the compliant joints comprised the double-curved cross-section shown in Figure 5i and the value of Wj was set at 2mm.

[0214] Figure 9 shows a graph 9 of the results of the first experiment. The x-axis shows strain as the change in length of the compliant scissor mechanism in the direction of longitudinal extension as a percentage of the length of the compliant scissor mechanism in the same direction when in the rest configuration. The y-axis shows the restoring force in Newtons exerted by the compliant scissor mechanism in the direction opposite the direction of extension. Line 91 of the graph 9 represents the results for the first example of the compliant scissor mechanism described in the preceding paragraph. Line 92 of the graph 9 represents the results for the second example of the compliant scissor mechanism. Line 93 of the graph 9 represents the results for the third example of the compliant scissor mechanism. Line 94 of the graph 9 represents the results for the fourth example of the compliant scissor mechanism. Line 95 of the graph 9 represents the results for the fifth example of the compliant scissor mechanism. Line 96 of the graph 9 represents the results for the sixth example of the compliant scissor mechanism.

[0215] The results of Figure 9 demonstrate that the shape of the cross-section of the compliant joints has less of an effect on the restoring force than the value of Wj. The gradient of each of lines 91 to 96 represents the stiffness of the respective compliant scissor mechanism in the direction of extension. The first example of the compliant scissor mechanism demonstrated the highest stiffness, and the sixth example of the compliant scissor mechanism demonstrated the lowest stiffness.

[0216] Isobaric blocking force evaluation

[0217] In a second experiment, the blocking force of the actuator of Figure 5a was evaluated. The longitudinal extension of the compliant scissor mechanism, i.e, the extension of the compliant scissor mechanism in the direction of the y-axis as shown in Figure 5d, was initially constrained to that of the rest configuration as shown in Figure 5d with respect to the first layer of the compliant scissor mechanism. The central inflatable chamber was then inflated to a constant pressure and the compliant scissor mechanism was gradually allowed to extend longitudinally. The force exerted by the actuator in the direction of the longitudinal extension was measured during the extension. This was repeated for three different values of constant pressure (5kPa, 30kPa, and 50kPa) for different examples of the actuator of Figure 5a.

[0218] The different examples of the actuator of Figure 5a included a first, second, and third example. For each example, the value of hb was set at 6mm, the value of Wj was set at 2mm, and each of the compliant joints comprised the rectangular cross-section shown in Figure 5g. In the first example, the actuator comprised the central inflatable chamber of Figure 6a. In the second example, the actuator comprised the central inflatable chamber of Figure 6b. In the third example, the actuator comprised the central inflatable chamber of Figure 6c.

[0219] Figure 10a shows a graph 101 of the results of the second experiment for the first example of the actuator of Figure 5a. The x-axis shows strain as the change in length of the compliant scissor mechanism of the actuator in the direction of extension as a percentage of the length of the compliant scissor mechanism in the same direction when in the rest configuration. The y-axis shows the force in Newtons exerted by the actuator in the direction of extension. Line 1011 shows the results when the constant pressure of the central inflatable chamber was 50kPa. Line 1012 shows the results when the constant pressure of the central inflatable chamber was 30kPa. Line 1013 shows the results when the constant pressure of the central inflatable chamber was lOkPa. The inset images in graph 101 show the actuator with the compliant scissor mechanism in the rest configuration (left-hand side) and with the compliant scissor mechanism at maximum longitudinal extension (right-hand side).

[0220] Figure 10b shows a graph 102 of the results of the second experiment for the second example of the actuator of Figure 5a. The x- and y-axes are as described above with respect to Figure 10a. Line 1021a shows the results when the constant pressure of the central inflatable chamber was 50kPa. Line 1022a shows the results when the constant pressure of the central inflatable chamber was 30kPa. Line 1023a shows the results when the constant pressure of the central inflatable chamber was lOkPa. The inset images in graph 102 show the actuator with the compliant scissor mechanism in the rest configuration (left-hand side) and with the compliant scissor mechanism at maximum longitudinal extension (right-hand side).

[0221] Line 1021b of graph 102 shows results for a reference actuator, which differs only in that the value of Wj is set at 4mm, when the constant pressure of the central inflatable chamber was 50kPa. Line 1022b shows results for the reference actuator when the constant pressure of the central inflatable chamber was 30kPa. Line 1022c shows results for the reference actuator when the constant pressure of the central inflatable chamber was lOkPa.

[0222] Figure 10c shows a graph 103 of the results of the second experiment for the third example of the actuator of Figure 5a. The x- and y-axes are as described above with respect to Figure 10a. Line 1031 shows the results when the constant pressure of the central inflatable chamber was 50kPa. Line 1032 shows the results when the constant pressure of the central inflatable chamber was 30kPa. Line 1033 shows the results when the constant pressure of the central inflatable chamber was lOkPa. The inset images in graph 103 show the actuator with the compliant scissor mechanism in the rest configuration (left-hand side) and with the compliant scissor mechanism at maximum longitudinal extension (right-hand side). As demonstrated by line 1033, there is a minimal change in force exerted by the actuator with an initial increase in strain up to a strain of around 87.5% when the constant pressure of the central inflatable chamber was lOkPa. Similarly, as demonstrated by line 1032, there is a minimal change in force exerted by the actuator with an initial increase in strain up to a strain of around 45% when the constant pressure of the central inflatable chamber was 30kPa. This is due to the central inflatable chamber expanding out of the plane of longitudinal extension of the compliant scissor mechanism during the initial increase in strain without expanding substantially in the plane of longitudinal extension of the compliant scissor mechanism, such that the force exerted on the compliant scissor mechanism by the central inflatable chamber remains substantially unchanged. As demonstrated by line 1031, this behaviour was not present when the constant pressure of the central inflatable chamber was 50kPa. This is due to the pressure within the central inflatable chamber causing sufficient expansion of the central inflatable chamber when the compliant scissor mechanism is in the rest configuration, such that the internal inflatable chamber expands substantially in the plane of longitudinal extension of the compliant scissor mechanism with an increase in longitudinal extension of the compliant scissor mechanism from the rest configuration, thereby resulting in a change in the force exerted on the compliant scissor mechanism by the central inflatable chamber with an increase in longitudinal extension.

[0223] The results of Figures 10a to 10c demonstrate an increase in force exerted in the direction of longitudinal extension for a given strain with an increase in the maximum volume of the central inflatable chamber. The results also demonstrate a minimal change in maximum strain of the compliant scissor mechanism with a central inflatable chamber of a given maximum volume as the constant pressure of the central inflatable chamber is increased. The maximum recorded force exerted in the direction of longitudinal extension of over 100N and the maximum recorded longitudinal strain of 178% were recorded for the third example of the actuator of Figure 5a when the internal pressure of the central inflatable chamber was 50kPa. The maximum recorded force represents a maximum force of 340 times the weight of the actuator.

[0224] Figure lOd shows a graph 104 of the results of the second experiment for the first, second, and third examples of the actuator of Figure 5a when the constant pressure of the central inflatable chamber was 50kPa. Line 1041 shows the results for the first example of the actuator. Line 1042 shows the results for the second example of the actuator. Line 1043 shows the results for the third example of the actuator. As shown in the graph 104, the force-strain profiles for the actuator of Figure 5a with internal inflatable chambers of different maximum volume inflated to a given constant pressure are substantially parallel, demonstrating predictable operating behaviour for different applications of the actuator.

[0225] The different examples of the actuator of Figure 5a further included a fourth, fifth, and sixth example. For each of these examples, the value of Wj was set at 4mm, each of the compliant joints comprised the rectangular cross-section shown in Figure 5g, and the actuator comprised the central inflatable chamber of Figure 6b. In the fourth example, the value of hb was set at 6mm. In the fifth example, the value of hb was set at 9mm. In the sixth example, the value of hb was set at 12mm.

[0226] Figure lOe shows a graph 105 of the results of the second experiment for the fourth, fifth, and sixth examples of the actuator of Figure 5a. Line 1051a shows the results for the fourth example of the actuator when the constant pressure of the central inflatable chamber was 50kPa. Line 105 lb shows the results for the fourth example of the actuator when the constant pressure of the central inflatable chamber was 30kPa. Line 1051c shows the results for the fourth example of the actuator when the constant pressure of the central inflatable chamber was lOkPa. Line 1052a shows the results for the fifth example of the actuator when the constant pressure of the central inflatable chamber was 50kPa. Line 1052b shows the results for the fifth example of the actuator when the constant pressure of the central inflatable chamber was 30kPa. Line 1052c shows the results for the fifth example of the actuator when the constant pressure of the central inflatable chamber was lOkPa. Line 1053a shows the results for the sixth example of the actuator when the constant pressure of the central inflatable chamber was 50kPa. Line 1053b shows the results for the sixth example of the actuator when the constant pressure of the central inflatable chamber was 30kPa. Line 1053c shows the results for the sixth example of the actuator when the constant pressure of the central inflatable chamber was lOkPa.

[0227] The results of Figure lOe demonstrate that at higher values of pressure of the central inflatable chamber, examples of the actuator of Figure 5a comprising a higher value of hb exert a greater force in the direction of the longitudinal extension at a given value of strain. The results also demonstrate similar trends in the force-strain relationship for examples of the actuator of Figure 5a comprising a higher value of hb at different values of pressure of the central inflatable chamber. It is believed that this behaviour is a result of an increased contact surface area between the compliant elements of the compliant scissor mechanism and the central inflatable chamber for examples of the actuator comprising a higher value of hb for given values of strain, thereby providing for greater transmission of force from the central inflatable chamber to the compliant elements.

[0228] Isometric force-strain evaluation

[0229] In a third experiment, an isometric force-strain evaluation was conducted on the actuator of Figure 7a. The longitudinal extension of the compliant scissor mechanism, i.e, the extension of the compliant scissor mechanism in the direction of the y-axis as shown in Figure 5d, was initially constrained to a set value while each central inflatable chamber was inflated concurrently towards a maximum value of 50kPa. The first and second lateral inflatable chambers were maintained at a constant pressure during inflation of the central inflatable chambers. It will be appreciated that there was an initial period of inflation of the central inflatable chambers before the central inflatable chambers began to exert a force on the compliant scissor mechanism. The maximum longitudinal extension of the compliant scissor mechanism was constrained from the initial constrained value. The exerted force of the compliant scissor mechanism was measured during inflation of the central inflatable chambers. The longitudinal extension of the compliant scissor mechanism from the initial set value was also measured. This was repeated for different examples of the actuator of Figure 7a.

[0230] The different examples of the actuator of Figure 7a included a first, second, and third example. For each example, the value of Wj was set at 4mm, each of the compliant joints comprised the rectangular cross-section shown in Figure 5g, and the actuator comprised the central inflatable chamber of Figure 6b. In the first example, the value of hb was set at 6mm. In the second example, the value of hb was set at 9mm. In the third example, the value of hb was set at 12mm. The weight of the compliant mechanism of the first, second, and third examples of the actuator was 67g, 77g, and 122g, respectively.

[0231] Figure I la shows a force-pressure graph 111 of the results of the third experiment for the second example of the actuator. The x-axis shows the internal pressure in kPa of the central inflatable chambers. The y-axis shows the force in Newtons exerted by the actuator in the direction of extension. The internal pressure of the first and second lateral inflatable chambers was maintained at OkPa. Line 1111 shows the results when the longitudinal extension of the compliant scissor mechanism was constrained to 10mm. Line 1112 shows the results when the longitudinal extension of the compliant scissor mechanism was constrained to 20mm. Line 1113 shows the results when the longitudinal extension of the compliant scissor mechanism was constrained to 30mm. Line 1114 shows the results when the longitudinal extension of the compliant scissor mechanism was constrained to 35mm. Line 1115 shows the results when the longitudinal extension of the compliant scissor mechanism was constrained to 40mm. Line 1116 shows the results when the longitudinal extension of the compliant scissor mechanism was constrained to 45mm. Line 1117 shows the results when the longitudinal extension of the compliant scissor mechanism was constrained to 50mm.

[0232] Figure 1 lb shows a force-strain graph 112 of the results of the third experiment for the second example of the actuator. The x-axis shows strain as the change in length of the compliant scissor mechanism of the actuator in the direction of extension as a percentage of the initially constrained value of length of the compliant scissor mechanism in the same direction. The y-axis shows the force in Newtons exerted by the actuator in the direction of longitudinal extension. The internal pressure of the first and second lateral inflatable chambers was maintained at OkPa. Line 1121 shows the results when the pressure of the central inflatable chambers was lOkPa. Line 1122 shows the results when the pressure of the central inflatable chambers was 20kPa. Line 1123 shows the results when the pressure of the central inflatable chambers was 30kPa. Line 1124 shows the results when the pressure of the central inflatable chambers was 40kPa. Line 1125 shows the results when the pressure of the central inflatable chambers was 50kPa. Line 1126 shows the maximum force measured for a given strain when deformation of the compliant scissor mechanism out of the plane of longitudinal extension was limited to 10mm.

[0233] Figure 11c shows a graph 113 of the maximum force measured for a given strain for each of the first, second, and third examples of the actuator for different values of constant pressure of the first and second lateral inflatable chambers. Line 1131 shows the results for the first example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to OkPa, i.e., when the first and second lateral inflatable chambers were substantially deflated. Line 1132 shows the results for the first example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to lOkPa. Line 1133 shows the results for the first example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to 30kPa. Line 1134 shows the results for the second example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to OkPa. Line 1135 shows the results for the second example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to lOkPa. Line 1136 shows the results for the second example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to 30kPa. Line 1137 shows the results for the third example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to OkPa. Line 1138 shows the results for the third example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to lOkPa. Line 1139 shows the results for the third example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to 3 OkPa.

[0234] The results of Figure 11c demonstrate that the maximum force exerted by the actuator of Figure 7a increases with an increase in the pressure of the first and second lateral inflatable chambers for each tested value of hb. The maximum recorded exerted force was 87N when the central inflatable chambers were inflated to 50kPa and the first and second lateral inflatable chambers were inflated to 3 OkPa.

[0235] Figure l id shows a graph 114 of the pressure of the central inflatable chambers at the maximum force measured for a given strain for each of the first, second, and third examples of the actuator for different values of constant pressure of the first and second lateral inflatable chambers. Line 1141 shows the results for the first example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to OkPa, i.e., when the first and second lateral inflatable chambers were substantially deflated. Line 1142 shows the results for the first example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to lOkPa. Line 1143 shows the results for the first example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to 30kPa. Line 1144 shows the results for the second example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to OkPa. Line 1145 shows the results for the second example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to lOkPa. Line 1146 shows the results for the second example of the actuator when the constant pressure of the first and second lateral inflatable chambers was set to 30kPa. Line 1147 shows the results for the third example of the actuator; for this example, the pressure of the central inflatable chambers always reached 50kPa, when deformation of the compliant scissor mechanism out of the plane of longitudinal extension was limited to 10mm, before the compliant mechanism could extend longitudinally from the initially constrained value.

[0236] The results of Figure l id demonstrate that the pressure of the central inflatable chambers at the maximum exerted force increases with an increase in longitudinal strain of the compliant scissor mechanism.

[0237] Over the test range of pressure of the central inflatable chambers, the lowest values of deformation of the compliant scissor mechanism out of the plane of longitudinal extension were achieved with the third example of the actuator, i.e., the actuator with the greatest value of hb, allowing the third example of the actuator to demonstrate the highest values of maximum exerted force and pressure of the internal inflatable chambers at maximum exerted force. The deformation of the compliant scissor mechanism out of the plane of longitudinal extension of the third example of the actuator never exceeded the constrained value of 10mm. As demonstrated by Figure 11c, at values of strain above around 88%, the third example of the actuator produced lower values of maximum restoring force compared to the other two examples, but the third example of the actuator produced the highest overall value of maximum restoring force of 87N when the pressure of the central inflatable chambers was 50kPa and the pressure of the first and second lateral inflatable chambers was 30kPa.

[0238] Comparing the results of Figures lOe and 11c shows that for a value of hb of 12mm, the actuator of Figure 5a and the actuator of Figure 7a exhibit similar force-strain behaviour. In contrast, for lower values of hb, the actuator of Figure 7a exhibits lower values of exerted force for a given value of strain for a given pressure of the first and second lateral inflatable chambers. It is believed that this is due to an increase in compliance of the actuator of Figure 7a out of the plane of longitudinal extension of the respective compliant mechanism. Figure 11c demonstrates that increasing the pressure of the first and second lateral inflatable chambers increases the maximum exerted force for a given value of strain. It is believed that this is due to a reduction in compliance out of the plane of longitudinal extension caused by an increase in pressure of the first and second lateral inflatable chambers.

[0239] Isotonic evaluation

[0240] In a fourth experiment, an isotonic evaluation was conducted on the actuator of Figure 5a and the actuator of Figure 7a. A load on the actuator acting in the direction opposite to the longitudinal extension of the compliant scissor mechanism, i.e, the extension of the compliant scissor mechanism in the direction of the y-axis as shown in Figure 5d, was varied and the inflatable chambers were inflated towards a maximum internal pressure of 50kPa as the longitudinal extension of the compliant scissor mechanism was measured. For the actuator of Figure 7a, the first and second lateral inflatable chambers and the central inflatable chambers were inflated to the same pressure at the same rate of inflation. The values of Wj and hb for both actuators were set at 4mm and 9mm, respectively.

[0241] Figure 12a shows a graph 121 of the results of the fourth experiment for the actuator of Figure 5a. The x-axis shows the internal pressure in kPa of the central inflatable chamber. The y-axis shows the longitudinal extension, i.e., longitudinal displacement, of the compliant scissor mechanism of the actuator from the rest configuration as shown in Figure 5d with respect to the first layer of the compliant scissor mechanism. Line 1211 shows the results when the load acting on the compliant scissor mechanism was 0.2kg. Line 1212 shows the results when the load acting on the compliant scissor mechanism was 1.2kg. Line 1213 shows the results when the load acting on the compliant scissor mechanism was 2.2kg. Line 1214 shows the results when the load acting on the compliant scissor mechanism was 3.2kg. Line 1215 shows the results when the load acting on the compliant scissor mechanism was 4.2kg.

[0242] Figure 12b shows the actuator 5 of Figure 5a in the rest configuration (left-hand side) and with the internal pressure of the central inflatable chamber at 50kPa (right-hand side) with a load of 4.2kg acting on the compliant scissor mechanism. The horizontal lines 1221 and 1222 demonstrate the longitudinal extension of the compliant scissor mechanism between the rest configuration and with the internal pressure of the central inflatable chamber at 50kPa. Figure 12c shows a graph 123 of the results of the fourth experiment for the actuator of Figure 7a. the x- and y-axes are as defined above with respect to Figure 12a. Line 1231 shows the results when the load acting on the compliant scissor mechanism was 0.2kg. Line 1232 shows the results when the load acting on the compliant scissor mechanism was 1.2kg. Line 1233 shows the results when the load acting on the compliant scissor mechanism was 2.2kg. Line 1234 shows the results when the load acting on the compliant scissor mechanism was 3.2kg. Line 1235 shows the results when the load acting on the compliant scissor mechanism was 4.2kg.

[0243] Figure 12d shows the actuator 7 of Figure 7a in the rest configuration (left-hand side) and with the internal pressure of the first and second lateral inflatable chambers and the central inflatable chambers at 50kPa (right-hand side) with a load of 4.2kg acting on the compliant scissor mechanism. The horizontal lines 1241 and 1242 demonstrate the longitudinal extension of the compliant scissor mechanism between the rest configuration and with the internal pressure of the first and second lateral inflatable chambers and the central inflatable chambers at 50kPa.

[0244] Figures 12a and 12c show an initial longitudinal extension below zero for the loads above 0.2kg as a result of compression of the compliant scissor mechanism of the respective actuator from the rest configuration under the applied load. In practice, this initial negative extension may be eliminated through control of the pressure of the inflatable chambers or by means of one or more mechanical spacers provided between the compliant elements of the respective compliant scissor mechanism units.

[0245] The results of Figures 12a and 12c demonstrate that the actuator of Figure 7a, i.e., an actuator with two compliant scissor mechanism units and first and second lateral inflatable chambers, can deliver approximately twice the extension of the actuator of Figure 5a, i.e., an actuator with a single compliant mechanism unit without lateral inflatable chambers, under an applied load of 4.2kg, which represents 55 times the weight of the actuator of Figure 7a. As such, the number of compliant mechanism units of the actuator can be scaled to a particular application.

[0246] Conclusion

[0247] The results of the four experiments described above demonstrate how the number and dimensions of the compliant mechanism units of the actuator, as well as the dimensions and maximum pressure of the inflatable chambers, can be varied to produce actuation and restoring forces suitable for a given application.

Claims

CLAIMS1. A wearable exoskeleton device, comprising: a compliant mechanism; and at least one force element configured to exert a force on the compliant mechanism to assist or support a desired articulation of a joint of the body of a wearer of the wearable exoskeleton device; wherein the compliant mechanism is configured to: i) resist articulations that are outside the desired articulation; and ii) substantially freely allow the desired articulation.

2. The device of claim 1, comprising: an actuator comprising the compliant mechanism and the at least one force element, wherein the at least one force element is configured to exert an actuation force on the compliant mechanism to assist the desired articulation; or a support element comprising the compliant mechanism and the at least one force element, wherein the at least one force element is configured to exert a support force on the compliant mechanism to support the desired articulation.

3. The device of claim 1 or claim 2, wherein the compliant mechanism comprises a first stiffness and a second stiffness, wherein the first stiffness defines the extent to which the compliant mechanism resists deformation in response to a force to affect the desired articulation and the second stiffness defines the extent to which the compliant mechanism resists deformation in response to a force to affect articulations that are outside the desired articulation, wherein the second stiffness is greater than the first stiffness.

4. The device of any preceding claim, wherein the articulations that are outside the desired articulation comprise articulations beyond a normal range of motion of the joint.

5. The device of claim 1 or claim 2, wherein the compliant mechanism comprises a compliant scissor mechanism.

6. The device of any preceding claim, wherein the compliant mechanism comprises at least one compliant mechanism unit, wherein the or each compliant mechanism unitcomprises a plurality of longitudinal compliant elements and a plurality of compliant joints, wherein the plurality of longitudinal compliant elements are connected together by the plurality of compliant joints, and wherein the plurality of longitudinal compliant elements are arranged to define an enclosed space.

7. The device of claim 6, wherein the plurality of longitudinal compliant elements and the plurality of compliant joints are integral.

8. The device of claim 6 or claim 7, wherein the at least one compliant mechanism unit comprises a plurality of compliant mechanism units, wherein the compliant mechanism comprises at least one compliant joint connecting each compliant mechanism unit to an adjacent compliant mechanism unit.

9. The device of any preceding claim, wherein the at least one force element comprises at least one inflatable chamber.

10. The device of claim 9, when dependent on claim 8, wherein the at least one inflatable chamber comprises at least one lateral inflatable chamber arranged between each compliant mechanism unit and an adjacent compliant mechanism unit.

11. The device of claim 10, wherein the plurality of compliant mechanism units comprises three or more compliant mechanism units, wherein the at least one lateral inflatable chamber comprises a lateral inflatable chamber arranged between each compliant mechanism unit and an adjacent compliant mechanism unit, and wherein the lateral inflatable chambers are in fluid communication with each other.

12. The device of claim 10, wherein the at least one lateral inflatable chamber comprises first and second lateral inflatable chambers arranged on opposite sides of the at least one compliant joint connecting the adjacent compliant mechanism units.

13. The device of claim 12, wherein the plurality of compliant mechanism units comprises three or more compliant mechanism units, wherein the first lateral inflatable chambers are in fluid communication with each other, and wherein the second lateral inflatable chambers are in fluid communication with each other.

14. The device of any of claims 9 to 13, when dependent on any of claims 6 to 8, wherein the at least one inflatable chamber comprises a central inflatable chamber arranged within the enclosed space of the or each compliant mechanism unit.

15. The device of claim 14, when dependent on claim 8, wherein the central inflatable chambers are in fluid communication with each other.

16. The device of any of claims 10 to 15, wherein the or each compliant mechanism unit comprises two layers, and wherein the or each lateral inflatable chamber and / or the or each central inflatable chamber is sandwiched between the two layers of a respective compliant mechanism unit of the or each compliant mechanism unit.

17. The device of any of claims 9 to 16, comprising control means to control the pressure of a fluid within the at least one inflatable chamber.

18. The device of claim 17, when dependent on claim 12 or claim 13, wherein the control means is configured to control the pressure of a fluid within the or each first lateral inflatable chamber independently of a pressure of a fluid within the or each second lateral inflatable chamber.

19. The device of claim 17 or claim 18, when dependent on claim 14 or claim 15, wherein the control means is configured to control the pressure of a fluid within the or each central inflatable chamber independently of a pressure of a fluid within the or each lateral inflatable chamber.

20. The device of any preceding claim, wherein at least a portion of a length of the compliant mechanism is straight when at rest.

21. The device of any of claims 1 to 19, wherein at least a portion of a length of the compliant mechanism is curved when at rest.

22. The device of any preceding claim, comprising two attachments for attaching the device to a part of the body of a wearer of the device above and below a joint of the body of the wearer, wherein the compliant mechanism extends between the two attachments.

23. The device of claim 22, wherein the part of the body of the wearer is a leg and the joint is a knee joint.

24. A method of fabricating the device of any of claims 1 to 23, the method comprising forming the compliant mechanism using additive manufacturing.

25. A method of fabricating the device of claim 16, or any of claims 17 to 23 when dependent on claim 16, wherein the method comprises: forming each of the two layers of the or each compliant mechanism unit; arranging the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of a respective compliant mechanism unit of the or each compliant mechanism unit; and securing the two layers of the or each compliant mechanism unit together to sandwich the or each lateral inflatable chamber and / or the or each central inflatable chamber between the two layers of the respective compliant mechanism unit.

Images