Field of the Invention

[0001] The present invention relates to a robotic exoskeleton apparatus.

[0002] The invention has been developed primarily to provide physical assistance to a human user, and more specifically movement assistance to the arm and shoulder of the user, in the context of rehabilitation and assistive living for patients with neurological disabilities or impairments resulting from conditions such as stroke, cerebral palsy or motor neuron disease. It should be appreciated, however, that the invention is not limited to this particular field of use, being potentially adaptable to any domestic, commercial, industrial or other environment in which physical assistance is necessary or advantageous for the performance of tasks. The invention may also be adapted to provide a mechanism for remote control or tele-operation of robotic arms.

Background of the Invention

[0003] The following discussion of the prior art is intended to place the invention in an appropriate technical context and enable its potential advantages to be more fully understood. However, any references to prior art should not be construed as an express or implied admission that such art is widely known or common general knowledge in the field.

[0004] It is known to use robotic exoskeletons to assist with rehabilitation and assistive living of neurologically impaired patients. In particular, it is known to use upper limb exoskeletons to support and replicate the movement of the shoulder. It is desirable for such devices to be light weight, low profile and non-intimidating. It is also important for these devices not to impede the user's normal range of motion, not to collide with the user, and to avoid any kinematic "singularities" in the mechanism. Satisfying all of these requirements simultaneously presents a significant technical challenge.

[0005] The glenohumeral (GH) joint at the shoulder complex is one of the most complex of the major joints, with the greatest range of movement (RoM), in the human body. It is essentially a ball and socket joint, enabling the humerus to rotate in three degrees of freedom (3DoF), to provide spherical motion . In order to replicate this movement, one known 3DoF shoulder exoskeleton apparatus creates a virtual ball and socket joint by means of three rotational joints. Two links, each effectively bent through 90°, are used to connect the three rotational joints, such that in use the rotational axes of the joints align at the centre of rotation of the GH joint, as shown for example in figure 1 .

[0006] This particular solution has several inherent problems. Firstly, kinematic singularities occur whenever joint axes align or become coplanar, effectively eliminating one degree of freedom from the mechanism. Controlling the robotic mechanism around these positions of singularity is difficult and inaccurate from a control perspective, and for the same reason is uncomfortable, disconcerting and potentially even dangerous for the user. More specifically, the difficulties arise when the mechanism attempts to perform rotations about the axis that has effectively been lost. This necessitates instantaneous changes in joint configuration, which in practice places excessive demands on actuators in terms of speed and acceleration, resulting in a combination of time delays, tracking errors and abrupt movements.

[0007] In an attempt to minimise the impact of these problems, high-performance components and more complex control algorithms may be used. However, this adds significantly to the overall cost and complexity of the device and the difficulties are nevertheless not fully overcome. The links may also be designed to position the rotational axes such that the singularities are less likely to be approached during normal use, having regard to the typical range of movement (RoM) of the shoulder joint. However, singularities still inevitably exist in the workspace of the human shoulder due to its extensive RoM, and accurate control in proximity to them is inherently impaired.

[0008] Another significant difficulty relates to the risk of collisions. In robotic exoskeleton configurations of the type shown in figure 1 , the robot can collide with itself or the user when endeavouring to reach certain arm positions, which in practice reduces the effective RoM of the robot.

[0009] In an attempt to ameliorate this problem, configurations have been proposed in which the last joint in the mechanism is positioned between the GH joint and the elbow, with the associated rotational axis aligned with the longitudinal axis of the upper arm of the user. This configuration is still capable of forming a virtual spherical joint at the shoulder, but reduces the number of joints and links around the shoulder itself, allowing for less collision risk and a greater RoM. An example of this configuration is shown in figure 2, wherein a C-shaped arcuate track and bearing assembly extends partially around the upper arm of the user, to define a rotational joint axis aligned with the upper arm.

[0010] A significant downside with this approach is that the resulting exoskeleton tends to become relatively large, heavy, cumbersome and intimidating. This is particularly due to the arcuate track and bearing assembly, which is required to be relatively large in order to substantially surround the user's upper arm while satisfying the inherent strength and RoM requirements. A related disadvantage is that the track itself then creates an increased collision risk and/or restricts the range of movement in certain positions and configurations.

[001 1] A further variation on this theme makes use of a bearing arrangement, configured to allow the user to slide the arm through the centre, as shown in figure 3. Again, this confers the requisite third degree of freedom for the mechanism. However, this configuration makes fitting and removing the exoskeleton difficult, and potentially impossible without assistance, depending upon the degree of impairment of the user. Also, by fully enclosing the upper arm, this configuration mechanically couples the user to the device to a substantially greater degree, which can be more intimidating and potentially more hazardous. Further variations along these lines are also known, but again tend to be relatively bulky, heavy, cumbersome and intimidating.

[0012] Current designs for assistive shoulder exoskeletons thus represent various significant trade-offs or compromises between the characteristics of a range of movement, singularity positions, size, weight and ease of use, with none simultaneously excelling in relation to these parameters.

[0013] It is an objective of the present invention to overcome or substantially ameliorate one or more of the disadvantages of the prior art, or at least to provide a useful alternative. Summary of the Invention

[0014] Accordingly, the invention provides a robotic exoskeleton apparatus adapted to provide assistive support for movement of a user's shoulder and glenohumeral (GH) joint, the apparatus including:- a base adapted to be supported adjacent a shoulder or upper arm of the user; a first link connected to the base by a first revolute joint defining a first degree of freedom;

a second link connected to the first link by a second revolute joint defining a second degree of freedom;

a third link connected to the second link by a third revolute joint defining a third degree of freedom;

a fourth link connected to the third link by a fourth revolute joint defining a fourth degree of freedom;

the links being connected in series and configured such that the respective axes of rotation of the revolute joints substantially coincide at an intersection point to form a virtual spherical joint with an instantaneous centre of rotation at the intersection point; the apparatus being supportable such that in use the instantaneous centre of rotation of the virtual spherical joint substantially coincides with the GH joint, with the links sufficiently spaced apart from the GH joint to avoid collision with the user; and the revolute joints collectively providing a redundant degree of freedom with respect to the virtual spherical joint, to facilitate control of the apparatus.

[0015] Preferably, the redundant degree of freedom (DoF) is utilised in conjunction with the configuration of the links to position any kinematic singularities substantially outside a normal range of movement of the GH joint corresponding to the normal operational workspace, thereby to facilitate control of the apparatus within the operational workspace.

[0016] In one embodiment, the fourth link is adapted for releasable connection to the upper arm of the user by means of an end-effector. In one embodiment, the end- effector is a passive element consisting essentially of a first connection mechanism such as a bracelet, sleeve, band or strap adapted for secure releasable connection around the upper arm of the user in the vicinity of the elbow joint. [0017] In some embodiments, the apparatus includes a fifth link connected to the fourth link by a fifth revolute joint and preferably having a rotational axis adapted to be aligned, in use, with the rotational axis of the elbow joint (i.e. with the fifth rotational axis extending transversely to the axis of the upper arm). In this embodiment, the fifth link is preferably adapted for connection to the forearm of the user, by means of a connection mechanism or end-effector, to provide active forearm movement assistance.

[0018] In one variation of this embodiment, the upper arm is supported directly by the fourth link, and the forearm is supported directly by the fifth link, and hence both the upper arm and forearm are actively supported via respective connection mechanisms, with the full range of movement of both the shoulder and the elbow being thereby simultaneously and independently replicated by the robotic exoskeleton.

[0019] In another variation of this embodiment, only the fifth link is connected directly to the user, and preferably to the forearm, by means of the associated end- effector, such that the robot provides direct support for the forearm only (the upper arm being thereby indirectly supported). In this case, it will be appreciated that the exoskeleton need not necessarily be connected directly to the upper arm. In some alternative embodiments, the fourth link may be connected to the upper arm.

[0020] In one embodiment, each of the revolute joints includes an independently operable actuation mechanism. In one form of this embodiment, the actuation mechanism is housed integrally within the revolute joint itself. In one such form, each actuator includes an electric servo motor, preferably with capacity to generate continuous torque of at least 8 Nm, and more preferably at least 15 Nm, at the respective joint.

[0021] In an alternative form of this embodiment, the actuation mechanism is located remotely, for example on the base, on an independent support platform of frame, in a backpack or harness worn by the user, or elsewhere as required. In such cases, drive transmission means are preferably provided to transmit drive from the respective actuation mechanisms to the associated joints. The drive transmission means may comprise gears, cables, belts, chains, mechanical linkages, hydraulic lines or other suitable drive transmission mechanisms, either individually or in combination. [0022] In another embodiment, due to the inherent kinematic redundancy of the apparatus, one of the joints is not independently actuated. Rather, two (or more) of the joints are optionally interconnected by a coupling mechanism, such that only three (or fewer) independent actuation mechanisms are required for effective operation, thereby reducing cost, weight and complexity. The coupling mechanism may comprise mechanical elements such as gears, cables, belts, chains, mechanical linkages or other suitable mechanical coupling means, either individually or in combination. In some embodiments, the coupling mechanism may additionally or alternatively include hydraulic, pneumatic, electrical, electro-mechanical, or electromagnetic means.

[0023] In yet other embodiments, a specific predetermined control constraint may be implemented between a selected pair or group of joints, so as to provide a defined kinematic coupling without a direct mechanical interconnection. In such embodiments, the kinematic coupling may be executed through the control software, in order to simplify the control strategy.

[0024] Preferably, the links are bent or otherwise shaped such that the exoskeleton is contoured in use to conform generally to the external profile of the adjacent shoulder region and upper arm of the user, and such that the distal fourth link moves in substantially side-by-side relationship with the upper arm of the user within the normal range of arm and shoulder movement.

[0025] Advantageously, none of the links surrounds or substantially surrounds the upper arm of the user, or has a rotational axis that is substantially coincident with or parallel to the upper arm of the user.

[0026] The apparatus preferably further includes a control system together with associated computer hardware and software, incorporating control algorithms to regulate movement of the joints and associated links of the exoskeleton , according to predetermined control constraints, methodologies or paradigms.

[0027] The control system and associated control algorithms are preferably optimised to allow full mobility and optimal control within the normal range of movement or operational workspace of the user's shoulder, while avoiding singularities, collisions and uncomfortable positions for the user.

[0028] In embodiments of the type previously described in which two or more of the revolute joints are mechanically interconnected, the control algorithms are preferably adapted to reflect or accommodate the specific nature of the kinematic connection between the interconnected joints.

[0029] In one preferred embodiment, the control methodology makes use of an assistance-as-needed (AAN) paradigm, configured to provide the user with a minimum level of assistance required to perform desired tasks, based on control parameters indicative of specified task requirements, related operator capabilities and an estimation of a resultant capability gap, wherein the estimated capability gap (if any) signifies a level of assistance that the robotic mechanism operating in the AAN paradigm should ideally provide.

[0030] In one embodiment, the apparatus includes, or is adapted for operative connection with, additional joints and links proximal to the shoulder, such that in use the position and/or orientation of the virtual spherical joint may be changed and controlled. The resultant additional proximal degrees of freedom allow the instantaneous centre of rotation of the virtual spherical joint to be selectively or controllably repositioned, thereby allowing alignment with the shoulder of the user to be maintained during shoulder movements such as retraction/protraction, elevation/depression, or a combination of such movements.

[0031] In another aspect, the invention provides a robotic exoskeleton apparatus adapted to provide assistive support for movement of a user's shoulder and glenohumeral (GH) joint, the apparatus including:- a base adapted to be supported adjacent a shoulder or upper arm of the user; a first link connected to the base by a first revolute joint defining a first degree of freedom;

a second link connected to the first link by a second revolute joint defining a second degree of freedom;

a third link connected to the second link by a third revolute joint defining a third degree of freedom; a fourth link connected to the third link by a fourth revolute joint defining a fourth degree of freedom;

the links being connected in series and configured such that the respective axes of rotation of the revolute joints substantially coincide at an intersection point to form a virtual spherical joint with an instantaneous centre of rotation at the intersection point, and such that the rotational axis of the fourth revolute joint is non-coaxial with respect to a longitudinal axis of the upper arm;

the apparatus being supportable such that in use the instantaneous centre of rotation of the virtual spherical joint substantially coincides with the GH joint, with the links sufficiently spaced apart from the GH joint to avoid collision with the user; and the revolute joints collectively providing a redundant degree of freedom with respect to the virtual spherical joint, to facilitate control of the apparatus.

[0032] In a further aspect, the invention provides a robotic exoskeleton apparatus adapted to provide assistive support for movement of a user's shoulder and glenohumeral (GH) joint, the apparatus including:- a base adapted to be supported adjacent a shoulder or upper arm of the user; a first link connected to the base by a first revolute joint defining a first degree of freedom;

a second link connected to the first link by a second revolute joint defining a second degree of freedom;

a third link connected to the second link by a third revolute joint defining a third degree of freedom;

a fourth link connected to the third link by a fourth revolute joint defining a fourth degree of freedom;

the links being connected in series and configured such that the respective axes of rotation of the revolute joints substantially coincide at an intersection point to form a virtual spherical joint with an instantaneous centre of rotation at the intersection point; the apparatus being supportable such that in use the instantaneous centre of rotation of the virtual spherical joint substantially coincides with the GH joint, with the links sufficiently spaced apart from the GH joint to avoid collision with the user;

wherein the revolute joints collectively provide a redundant degree of freedom with respect to the virtual spherical joint, and wherein the redundant degree of freedom is utilised to enable two or more of the joints to be kinematically connected by a kinematic coupling mechanism, to facilitate control of the apparatus. [0033] In one preferred embodiment of this aspect, the apparatus includes only three (or fewer) independently operable actuation mechanisms, associated respectively with a predetermined set of three of the revolute joints, with the fourth joint being kinematically coupled with one (or more) of the other three joints, via the kinematic coupling mechanism.

[0034] In this way, various advantages of a 4-DoF mechanism are achieved with the cost-effectiveness and control simplicity of a mechanism only requiring three independent actuators. In this embodiment, the rotational axis of the fourth joint may or may not be coaxially aligned with the longitudinal axis of the upper arm.

Brief Description of the Drawings

[0035] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

[0036] Figure 1 is a diagrammatic perspective view showing a robotic exoskeleton with three degrees of freedom (3DoF), adapted to support movement of the shoulder joint of the user, in accordance with a first known apparatus from the prior art;

[0037] Figure 2 is a diagrammatic perspective view similar to Figure 1 , showing a second apparatus from the prior art, again with 3DoF, in which one degree of freedom of movement is provided by means of an arcuate track and bearing assembly extending around the upper arm of the user, such that the third rotational axis is aligned with the upper arm;

[0038] Figure 3 is a diagrammatic perspective view of a third robotic exoskeleton apparatus from the prior art, in which the arm of the user slides through an outer rotational track and bearing assembly such that the apparatus substantially surrounds the upper arm and forearm of the user;

[0039] Figure 4 is a diagrammatic perspective view showing a robotic exoskeleton apparatus according to a first embodiment of the present invention;

[0040] Figure 5 is a plan view showing the apparatus of Figure 4, with the links and joints disposed in a nested configuration; [0041] Figures 6A to 6I are a series of diagrammatic perspective views of the apparatus of Figures 4 and 5 operable in conjunction with a user, showing different positions of the shoulder and forearm within the normal range of movement;

[0042] Figure 7 is an enlarged more detailed perspective view of the apparatus 4 to 6, attached to a floor-mounted support frame;

[0043] Figure 8 is a perspective view showing the apparatus of Figure 7 fitted to a user, seated on a chair;

[0044] Figure 9 is a perspective view showing the apparatus of Figures 7 and 8 detached from the user, with the links and joints disposed in a nested configuration;

[0045] Figure 10 is a perspective view showing a further embodiment of the invention, incorporating a handle formation in place of sleeves for engagement by the operator; and

[0046] Figure 1 1 is a perspective view showing yet another embodiment of the invention, incorporating a supplementary frame or mechanism attached to the fifth link, and a tool operatively attached to the supplementary mechanism.

Preferred Embodiments of the Invention

[0047] Referring to the drawings, Figure 1 is a diagrammatic representation of a first configuration based on the prior art, showing a robotic exoskeleton apparatus 1 adapted to provide assisted support for movement of a user's glenohumeral (GH) shoulder joint. The apparatus 1 includes a base 2 adapted to be supported behind the shoulder 3 of the user and a series of three links 4 and three intermediate rotational joints 5. These links and joints form a kinematic chain with three degrees of freedom (3DoF) and are positioned to replicate the movement of the GH shoulder joint of the user, which can be modelled as a 3DoF spherical ball and socket joint. A series of actuators (not shown) are used to control rotation of the links around the respective joints pursuant to a predetermined control methodology.

[0048] As discussed in the preamble, this configuration is subject to a number of inherent constraints and difficulties, particularly related to the kinematic singularities that inevitably occur when the first and third axes align (in a relative orientation of either 0° or 180°), effectively eliminating one degree of freedom from the mechanism. Controlling the mechanism at and around these singular configurations becomes difficult and less accurate from a control perspective as well as becoming uncomfortable, clunky and potentially dangerous from the user's perspective.

[0049] Although providing a virtual spherical joint with 3DoF, this configuration typically involves the two intermediate links in the kinematic chain being effectively bent through 90°, in order to allow the axes of rotation of the respective joints to coincide at an instantaneous centre of rotation 8, corresponding in use to the rotational centre of the GH joint, while facilitating manipulation of the end-effector. These constraints limit the ability to optimise the shape and minimise the overall size of the exoskeleton.

[0050] In an attempt to ameliorate these problems, the arrangement of Figure 2 has also been proposed in the prior art. In this configuration, the third rotational joint 5A is positioned between the GH joint and the elbow of the user, with the associated axis of rotation aligned with the upper arm. This configuration is capable of forming a virtual spherical joint with 3DoF at the shoulder, and advantageously reduces the number of links and joints around the shoulder itself, potentially allowing a greater range of movement. In practice, however, it requires a large C-shaped arcuate track and bearing assembly 7 to extend around the upper arm, in order to define the rotational joint axis aligned with the upper arm. Consequently, the resulting exoskeleton becomes relatively large, heavy, cumbersome and potentially intimidating to use. Moreover, the arcuate track and bearing assembly 7 creates an increased collision risk with the user and/or with other links or joints.

[0051] In an attempt to address these problems, a further variation on this theme is also known from the prior art, as shown Figure 3. In this case, a bearing assembly 5A, constituting the third rotational joint, is configured to allow the user to slide the upper arm through the centre of the joint, such that the joint and the associated Link completely surround the upper arm. However, as previously discussed, this makes fitting and removing the exoskeleton difficult and potentially impossible without assistance, depending upon the degree of impairment of the user. It also effectively encloses the arm of the user within the device to a substantially greater degree, which can be more intimidating and also potentially more hazardous for the user.

[0052] Referring now to Figures 4 to 9, the invention provides a robotic exoskeleton apparatus 10 adapted to provide assistive support for movement of the user's GH shoulder joint.

[0053] The apparatus includes a base 12 adapted to be supported adjacent and typically behind the shoulder 14 of the user. The base may be connected to a fixed supporting structure or frame 15 (see figures 7 to 9) or may be supported by the user by means of a wearable apparatus such as a harness, backpack or the like. In some embodiments, the base may alternatively be connected to the frame of a wheelchair, a walking frame or other mobile support structure.

[0054] The apparatus 10 includes a first link 16 connected to the base 12 by a first revolute joint 18 to define a first degree of freedom for the kinematic mechanism. A second link 20 is connected to the first link 16 by means of a second revolute joint 22 to define a second degree of freedom. A third link 24 is connected to the second link 20 by a third revolute joint 26 defining a third degree of freedom. A fourth link 28 is connected to the third link 24 by a fourth revolute joint 30, defining a fourth degree of freedom for the mechanism.

[0055] The fourth link is adapted for releasable connection to the upper arm 32 of the user by means of an end-effector 34 in the form of a band, sleeve, cuff, strap or the like (omitted from figures 6A to 6I for clarity). In one preferred embodiment, as shown in figures 7 to 9, the connecting mechanism takes the form of a relatively rigid lower semi-cylindrical half-sleeve 35 operable in conjunction with a relatively flexible adjustable upper "Velcro" strap 36 adapted for releasable snug-fitting engagement around the user's upper arm. In this way, the strap 36, which may optionally be elasticised, is adapted releasably to retain the upper arm in supportive engagement with the relatively rigid half-sleeve 35 and hence operatively connected to the end- effector 34.

[0056] As best seen in Figure 4, the links are connected in series and configured such that the axes of rotation of the respective revolute joints 18, 22, 26 and 30 substantially coincide at an intersection point X, thereby in combination to form a virtual spherical joint with an instantaneous centre of rotation (ICoR) at the intersection point X. By means of the base 12, the exoskeleton is adapted to be supported such that, in use, the instantaneous centre of rotation (ICoR) X of the virtual spherical joint substantially coincides with the GH joint, with the links sufficiently spaced apart from the GH joint to avoid collision or interference with the user.

[0057] It will be appreciated that the GH joint, which is essentially a ball and socket joint, permits rotation with three degrees of freedom (3DoF) to provide the requisite spherical motion of the shoulder joint. Importantly, however, in this configuration of the present invention, the four revolute joints 18, 22, 26 and 30 collectively provide 4DoF, although the end-effector 34 itself is only capable of spherical motion about the instantaneous centre of rotation, with 3DoF. Thus, by providing 4DoF in a kinematic mechanism with only 3DoF of motion at the end-effector, the mechanism provides one redundant DoF.

[0058] The inherent redundancy resulting from this configuration is utilised in conjunction with optimised link design to position the kinematic singularities substantially outside the normal range of movement of the GH joint, thereby to facilitate optimal control of the apparatus within the normal range of shoulder movement, as illustrated for example in figures 6A to 6I, and as described more fully below. Moreover, this improved functionality is achieved without requiring the rotational axis of the last joint in the mechanism to be substantially coaxial with the upper arm, thereby removing the need for a large diameter circular or arcuate track or bearing assembly extending partially or fully around the upper arm.

[0059] In one embodiment of the invention, as best seen in figures 7 to 9, the apparatus optionally includes a secondary fifth link 40, connected to the fourth primary link 28 by a fifth revolute joint 42 having a rotational axis adapted for alignment, in use, with the rotational axis of the user's elbow joint. In this case, the fifth link 40 is adapted for connection to the forearm of the user, again by means of a relatively rigid lower semi-cylindrical half-sleeve 45 operable in conjunction with a relatively flexible adjustable upper "Velcro" strap 46 adapted for releasable snug-fitting engagement around the user's forearm, to provide assistance with forearm movement. In this way, both the upper arm and forearm are actively supported, with the full range of movement of both the shoulder and elbow joints being simultaneously and independently replicated by the robotic exoskeleton.

[0060] In one preferred form of the invention as illustrated, each of the revolute joints includes an independently operable actuator 50, integrally housed within the revolute joint itself. Each actuator includes an electric servo motor, preferably with a capacity to generate continuous torque of at least 15Nm at the associated joint. An example of a revolute joint with integral actuation mechanism suitable for this purpose is manufactured by Kinova Robotics under the "Jaco" name. These units are back- driveable when shut down, have substantially zero backlash, a maximum rotational speed of around 8 rpm, nominal joint torque of around 30 Nm and are powered electrically by a 24 V DC supply.

[0061] In other embodiments, however, one or more of the actuators may be located remotely, for example on the base, on an independent support platform or frame, in a backpack or other support structure worn by the user, in a wheelchair associated with the apparatus, or elsewhere as required. In such cases, drive transmission means (not shown) are provided to transmit drive from the remote actuators to the associated joints. The drive transmission means may comprise gears, cables, belts, chains, mechanical linkages, hydraulic lines or other suitable transmission mechanisms, either individually or in combination. Such embodiments provide the significant advantage of substantially reducing the size and weight of the links and joints, while also effectively increasing the output force for a given capacity of actuator, due to the reduced mass of the exoskeleton required to be overcome.

[0062] In one preferred form of the invention, due to the inherent kinematic redundancy of the apparatus, one of the primary joints is not independently actuated. Rather, two or more of the joints are mechanically interconnected by a direct coupling mechanism, such that only three (and potentially fewer) independent actuation mechanisms are required for effective operation of the four primary revolute joints that together form the virtual spherical shoulder joint. The coupling mechanism linking the interconnected joints may again take any suitable form including gears, cables, belts, chains, mechanical linkages, hydraulic lines or other viable coupling mechanisms, configured either individually or in combination. In a variation of this embodiment, none of the joints are mechanically interconnected, but a selected pair or group of joints is kinematically or "virtually" coupled on the basis of a predetermined relatively straightforward kinematic function, so as to simplify the overall control methodology.

[0063] As best seen in figures 7 to 9, the links are bent, curved or otherwise shaped such that the exoskeleton is contoured to conform generally to the external profile of the shoulder region and upper arm of the user, and such that the distal fourth link 28 moves in substantially side-by-side relationship with the upper arm of the user, within the normal range of arm and shoulder movement. Although the primary first, second, third and fourth links are shown in the illustrated embodiments as being curved through particular angles of approximately 45°, it should be appreciated that as another advantage of the inherent redundancy of the kinematic mechanism, this need not be the case. In particular, the removal of this constraint allows the size, shape and configuration of the links and joints to be tailored more closely and economically to the shoulder and arm profile of the user, while still achieving the full range of movement throughout the desired operational workspace.

[0064] A further embodiment of the invention is shown in figure 10, wherein similar features are denoted by corresponding reference numerals. In this case, it will be seen that the half-sleeves 35 and 45 and the associated Velcro straps 36 and 46 are omitted, and in their place a handle 60 is provided. The handle may be attached directly to the fifth link 40, as shown, or in other embodiments may be attached to the fourth link. In some embodiments, the handle may be part of, or substituted by, a tool attached to the end of the robot (for example to the end of the fifth link), which the operator may hold directly. These embodiments are particularly well adapted for use in industrial applications to facilitate the operation of heavy tools, or tools that typically impart relatively high reactive loads to the operator. In further variations, the handle formation may be provided in addition to the half-sleeve or cuff based attachment mechanisms previously described.

[0065] A further embodiment is shown in figure 1 1 . In this case, it will be seen that the handle 60 is not attached directly to the fifth link of the exoskeleton, but rather is attached to a supplementary frame or mechanism 62 (optionally a "wrist" mechanism with additional joints and links), which in turn is attached to the fifth link, (or another link), of the robot. As will be seen, a tool 64 or similar implement is also attached to the supplementary mechanism 62. In some embodiments, the handle 60 may be integral with, or substituted by, the tool itself, if required, additional actuators may also be incorporated into the supplementary mechanism 62. In this embodiment, the tool 64 includes another handle 66 to be gripped by the other hand of the operator, for additional stability, support and control. Once again, embodiments of this type are particularly well adapted for use in industrial applications to facilitate the operation of heavy or high-load tools and equipment, but are not limited to such applications.

[0066] The apparatus further includes a control system implemented through a computer system incorporating microprocessors, data storage media, output displays and the like as required. The control system incorporates control algorithms to regulate the movement of the joints and links of the exoskeleton, by means of the actuation mechanisms previously described.

[0067] The control system and associated control algorithms are ideally optimised to allow full mobility and optimal control within the normal range of movement of the shoulder and upper arm, while avoiding singularities, collisions and uncomfortable transient positions for the user. In particular, the redundant degree of freedom is ideally specifically utilised in the control software on the basis of specific control objectives, such as orientation of the upper arm via kinematic configurations that are distanced as far as possible from undesirable singularities.

[0068] it is also possible to introduce a specific control constraint between two or more of the joints, for example a simple linear constraint such as ^■ ¾ = a% + &.

Although executable through the control software in order to simplify the overall control strategy, a straightforward constraint of this nature may also be implemented in a purely mechanical fashion, for example by means of a simple belt & pulley or chain & sprocket drive mechanism extending between two joints of the exoskeleton. As previously foreshadowed, this mechanical interlinking of joints at least obviates the need for a fourth actuator and hence reduces the associated weight, cost and complexity. Depending upon the number of joints that are kinematically coupled, the number of actuators may be further reduced.

[0069] Subject to these sorts of considerations, specific methodologies fo constructing robotic control algorithms are well known to those skilled in the art, and so will not be described in detail. However, one aspect to be noted is that because of the inherent redundancy, the mechanism can achieve any given position of the end- effector in a variety of different link and joint configurations, which gives rise to an infinite number of inverse kinematic solutions, which does complicate the control methodology from the kinematic perspective. One strategy to address this complication is to identify an optimal joint configuration for any position of the distal link within the workspace. Various optimisation strategies, control algorithms and supplementary constraints can be used to simplify this process. One approach involves a subdivision or discretisation of the active workspace into a predetermined number of uniformly distributed points or nodes, corresponding to end-effector positions at which joint configurations are specifically analysed, ensuring that singularities are avoided and all other constraints are optimally satisfied.

[0070] In one preferred form of the invention, the control methodology makes use of an assistance-as-needed (AAN) paradigm, configured to provide the user with a level of assistance appropriate for performing desired tasks, based on control parameters indicative of specified task requirements, related operator capabilities and an estimation of any resultant capability or performance gap, wherein the estimated capability or performance gap signifies a level of assistance that the robotic mechanism operating in the AAN paradigm should ideally provide.

[0071] The AAN paradigm thus aims to control an assistive robot so as to provide its human operator with the minimum assistance required to perform desired tasks. Generally, a human has some amount of capability to perform a desired task, and the task requires some amount of capability for it to be performed adequately. If there exists a capability gap, then this gap signifies the degree of assistance that a robot operating in the AAN paradigm should ideally provide the human. The AAN paradigm is applicable in many applications, but has gained particular focus in robotic rehabilitation. In therapy for disabilities such as stroke, patient active participation is essential for motor-neuron recovery. AAN has been shown to be well suited for this application as it inherently promotes active participation by providing the minimal assistance the patient requires during therapy.

[0072] The main challenge in providing AAN is determining the true assistance needs of the human operator, such that the robot can provide it at the appropriate level. This requires assistance to be adapted based on the difficulty of the task, which may vary throughout its execution, over time, or randomly from external disturbances. Secondly, and more challenging, assistance is required to be adapted based on the operator's capability to perform the task. Physical capability varies from person to person, and in rehabilitation applications this is exacerbated by impairment specific to the individual. A solution is for the robot to infer the operator's assistance needs empirically from the task performance. This approach, sometimes named performance-based assistance, critiques past performances of an operator with respect to some predefined criterion. Examples include the minimum jerk movement of the hand, step height achieved during walking, and kinematic error between the hand and goal location during reaching tasks. Assistance is governed by changing performance, i.e., as the operator's performance improves the assistance is reduced. This is combined with a strategy that continually challenges the operator over time, such as a forgetting factor. This is required as performance-based assistance promotes "slacking" as the human motor system exploits the assistance provided to minimise its own physical effort.

[0073] Performance-based methods of providing AAN have inherent limitations due to their empirical nature. For example, numerous observations are required before the operator's assistance needs can be determined. Additionally, if assisting several different tasks, each with individual assistance needs, then numerous observations for each task are required.

[0074] The proposed AAN paradigm uses parameters from a musculoskeletal model (MM) representing the operator's upper limb to calculate strength at the hand. The capability of the operator is defined at the muscular level, and is applied to a task using an optimization model to determine the relevant strength capability. This is compared to the strength required to perform the task to gauge the need for assistance.

[0075] This approach has several advantages over empirical-based methods, such as allowing a predictive estimate of an operator's assistance needs for tasks not yet observed. The benefits and limitations of this approach as compared with alternative approaches, and an outline of how it may be utilised to control an assistive robot, are described in a research paper entitled "Estimating Physical Assistance Need Using a Musculoskeletal Model" by Marc G. Carmichael and Dikai Liu (IEEE Transactions on Biomedical Engineering, Vol. 60, No 7, July 2013), the full contents of which are hereby incorporated by cross-reference. It should be understood, however, that this is simply an example of one control paradigm that may be adapted for use with the robotic exoskeleton of the present invention. Numerous other control strategies and paradigms may additionally or alternatively be utilised, subject to the intended application, and other factors.

[0076] Although the invention has been described primarily in the context of rehabilitation or assisted living for neurologically impaired patients, it should be appreciated that the invention has a number of other significant applications. For example, in commerce and industry, tasks that are physically intensive for able-bodied workers can often lead to a range of personal injuries such as muscular skeletal disorders (MSDs). Some tasks of this type such as baggage handling, warehouse stocking and the like can involve repeated short bursts of intensive effort as bags or goods are moved manually from one place to another. Other tasks such as manipulating shotblasting nozzles that generate a constant reaction force can involve sustained effort in one position for prolonged periods of time.

[0077] In both cases, the robotic exoskeleton apparatus as described may be adapted to provide additional force, or support when required, without substantially impeding the movement of the operator and without substantially compromising the extent of operator control of the device, equipment or goods being manipulated. Embodiments developed for industrial applications may, of course, require substantially more powerful actuators, and appropriately tailored robotic control algorithms. In particular, the AAN paradigm may be tailored not so much to provide a minimum level of assistance required by the operator to perform the specified task, but rather a sufficient level of assistance to minimise the risk of injury, as a result of a physically intensive task being performed on a highly repetitious or sustained basis.

[0078] The invention may also be adapted to provide a mechanism for remote control or tele-operation of robotic arms, as distinct from assistive movement or support for the user. In such applications, the operator wears the exoskeleton as a master device, which typically via a control interface, sends positional information to a slave robot and thereby permits the operator to remotely control movement of the slave robot. [0079] The invention at least in its preferred embodiments provides a robotic exoskeleton apparatus adapted to replicate and support the complex array of movements of the human shoulder, in a way that avoids a number of problems and limitations of prior art. In particular, the redundant degree of freedom allows the apparatus to be designed so as to avoid kinematic singularities and thereby enhance controllability throughout the operational workspace. The size and shape of the various links and joints can be tailored to minimise bulk, weight, visual impact, and collision risk without the need for large circular tracks or bearings extending around the arm or shoulder of the user. Furthermore, joints can be coupled mechanically or kinematically paired, to avoid the need for a fourth independent actuator or to simplify the control methodology, if desired. Notably also, the rotational axis of the fourth revolute joint is not required to be aligned with the upper arm, thereby obviating the need for any large track or bearing assemblies extending around the arm, or through which the arm of the user must extend. In these and other respects, the invention represents a practical and commercially significant improvement over the prior art.

[0080] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.