Forearm assistive device

Abstract

A powered orthotic device (26) for providing powered assistance to a forearm of a human user. The device (10) comprises a proximal orthosis (16) and a distal orthosis (18) for mounting the device (10) to a user's arm, and a forearm joint (22) coupling the proximal orthosis (16) to the distal orthosis (18). The forearm joint (22) is configured as a remote centre of motion joint to allow the distal orthosis (18) to rotate relative to the proximal orthosis (16) about a longitudinal rotation axis (26) positioned laterally distal to the device (10). A forearm actuator (28) is configured to actuate the forearm joint (22) to rotate the distal orthosis (16) relative to the proximal orthosis (18) about the longitudinal rotation axis (26). A sensor unit (31) comprising one or more sensors (32) is configured to provide a first sensor output indicating a torque transferred from the distal orthosis (18) to the proximal orthosis (16) through the forearm joint (22). A controller (30) is communicatively coupled with the sensor unit (31) and the forearm actuator (28), and configured to operate the forearm actuator (28) to actuate the forearm joint (22) to rotate the distal orthosis (18) based on the first sensor output.

Description

[0001] 174364 / 01

[0002] FOREARM ASSISTIVE DEVICE

[0003] TECHNICAL FIELD

[0004] This disclosure relates to powered orthotic devices, particularly for providing powered assistance to forearm and / or hand gripping movements by a human user.

[0005] BACKGROUND

[0006] Assistive orthotic medical devices exist to support a user in the functional activities of daily living. A user may have a motor impairment in a limb, for example as a result of a medical condition such as a stroke or a brachial plexus injury. Such an impairment may affect an upper limb, meaning that the user’s arm is severely weakened, making several activities very difficult or impossible. Support for the upper limb, to help the user with arm function, may be provided by a passive orthotic device, such as a brace, or a powered orthotic device that uses a power source, such as a battery, to actively support the upper limb and provide powered assistance to limb movements. A powered orthotic device may also be used by people with motor impairment in both upper limbs or by people without motor impairments to enhance their strength or mobility.

[0007] Known powered orthotic devices use electromyography (EMG) to measure the remaining electrical muscle activation signals directly on the skin above a muscle in the impaired arm. This information is used to determine how to provide powered assistance to the arm movements or grasp of the user. However, EMG has significant drawbacks for users of powered orthotic devices.

[0008] EMG utilizes electrodes placed on the skin above a muscle. To get sufficient signal quality, the placement of these electrodes must be accurate. The user must place these electrodes every time they are putting the device on, which complicates the process of putting the device on. This process also introduces potential differences in the interaction every time the device is used. Some muscle areas may present particular difficulties for electrode placement by a user - for example, the smaller muscles of the forearm and hand may require even more precise placement, and the user would only have one hand available to place the electrodes on the forearm and hand. EMG electrodes placed on the wrists and hands may particularly get in the way when a user is carrying out daily activities.

[0009] For gripping assistance, it is known to use pressure sensors in the fingertips of a device such as a glove to recognize a collision with an object and followingly the intention to grasp that object. This pressure sensor concept requires some control of the movement / force of the fingers to operate the device. This can be difficult for users with a clenched or a flaccid hand. The fingertip sensor also requires quite accurate placement of the sensors on the fingers when the device is put on, and also as the fingers move to form a grip. A soft glove with pressure sensors can be very difficult to put on for someone with a clenched hand, or with a flaccid hand that cannot provide any help to the user. Furthermore, EMG electrodes must be placed on exposed skin. This restricts which clothing the user can wear while operating the device. This can be problematic for users with medical conditions that cause blood flow to the extremities to be restricted, resulting in the users being cold.

[0010] WO2016 / 205356A1 discloses a powered orthotic device for a limb that uses EMG sensors to detect activity in a user’s muscles, and applies a torque to a brace system based on the sensor output to assist a user’s motion.

[0011] US2019 / 01575376A1 discloses a powered orthotic device including a brace, a finger engagement member, a thumb engagement member and a hand actuator. The hand actuator causes the finger engagement member to move relative to the thumb engagement member. The hand actuator may be operated based on EMG sensor signals.

[0012] There is a need for an improved powered orthotic device to assist users with carrying out functional daily activities.

[0013] SUMMARY

[0014] An aspect of the present disclosure provides a powered orthotic device for providing powered assistance to a forearm of a human user, the device comprising: a proximal orthosis and a distal orthosis for mounting the device to a user’s arm, the proximal orthosis configured to be mounted at a proximal position on the user’s arm and the distal orthosis configured to be mounted at a distal position on the user’s forearm and / or hand; a forearm joint coupling the proximal orthosis to the distal orthosis to define an orthosis longitudinal axis extending from the proximal orthosis to the distal orthosis, such that, when the device is mounted to the user’s arm, the orthosis longitudinal axis is substantially parallel to a longitudinal axis of the user’s forearm, wherein the forearm joint is configured as a remote centre of motion joint to allow the distal orthosis to rotate relative to the proximal orthosis about a longitudinal rotation axis positioned laterally distal to the device, the longitudinal rotation axis substantially parallel to the orthosis longitudinal axis; a forearm actuator configured to actuate the forearm joint to rotate the distal orthosis relative to the proximal orthosis about the longitudinal rotation axis; a sensor unit comprising one or more sensors configured to provide a first sensor output indicating one or more torques transferred from the distal orthosis to the proximal orthosis through the forearm joint; and a controller communicatively coupled with the sensor unit and the forearm actuator, the controller configured to operate the forearm actuator to actuate the forearm joint to rotate the distal orthosis based on the first sensor output.

[0015] In some embodiments of the above, the forearm joint is configured such that, when the device is in use and mounted to a user’s arm, the distal orthosis rotates relative to the proximal orthosis about the longitudinal rotation axis in response to the user’s forearm exerts a force for a pronation or supination.

[0016] In some embodiments of any of the above, the one or more sensors are configured to, in use, provide the first sensor output indicating one or more torques transferred from the distal orthosis to the proximal orthosis through the forearm joint due to the user’s forearm exerting force for the pronation or supination.

[0017] In some embodiments of any of the above, the controller is configured to operate the forearm actuator such that, in use, the forearm actuator actuates the forearm joint to rotate the distal orthosis based on the first sensor output to assist the user in performing the pronation or supination.

[0018] In some embodiments of any of the above, the forearm actuator comprises a forearm actuator output rigidly coupled to the sensor unit, and the distal orthosis is rigidly coupled to the forearm joint via the sensor unit, such that an external torque applied to the distal orthosis and a torque produced by the forearm actuator at the forearm actuator output are transmitted through the sensor unit.

[0019] In some embodiments of any of the above, the controller is programmed to activate the forearm actuator if the first sensor output indicates a torque or velocity beyond a predetermined first forearm threshold value.

[0020] In some embodiments of the above, the controller is programmed not to activate the forearm actuator if the first sensor output indicates a torque that does not surpass the predetermined first forearm threshold value.

[0021] In some embodiments of any of the above, the controller is configured to control the forearm actuator to produce a predetermined torque or velocity to rotate the distal orthosis for a predetermined period of time when the first sensor output indicates a torque beyond the predetermined first forearm threshold value.

[0022] In some embodiments of any of the above, the device further comprises an inertial measurement unit (I MU) coupled to the distal orthosis and communicatively coupled to the controller, the IMU configured to measure and output one or more IMU signals indicating velocity and acceleration of the distal orthosis, wherein the controller is configured to operate the forearm actuator additionally based on the one or more IMU signals.

[0023] In some embodiments of any of the above, the device further comprises a finger orthosis for coupling the device to one or more fingers of the user’s hand, the finger orthosis coupled to the distal orthosis at a finger joint, the finger joint configured to allow the finger orthosis to pivot relative to the distal orthosis about a lateral gripping axis substantially perpendicular to the orthosis longitudinal axis; and a finger actuator configured to actuate the finger joint to rotate the finger orthosis relative to the distal orthosis about the lateral gripping axis.

[0024] In some embodiments of the above, the sensor unit comprises one or more wrist sensors configured to provide a second sensor output indicating a torque transferred from the distal orthosis to the proximal orthosis through the forearm joint about a wrist axis substantially perpendicular to the orthosis longitudinal axis, wherein the wrist axis is either a wrist flexion / extension axis oriented substantially parallel to the lateral gripping axis to correspond to the user’s wrist flexion / extension axis when the device is mounted to the user’s arm, or a wrist ulnar / radial deviation axis oriented substantially perpendicular to the lateral gripping axis to correspond to the user’s wrist ulnar / radial deviation axis when the device is mounted to the user’s arm; and the controller is communicatively coupled with the finger actuator, the controller configured to operate the finger actuator to actuate the finger joint based on the second sensor output.

[0025] In some embodiments of the above, the controller is configured to operate the forearm actuator to actuate the forearm joint to rotate the distal orthosis additionally based on the second sensor output.

[0026] In some embodiments of any of the above, the controller is programmed to operate the forearm actuator to actuate the forearm joint if the first sensor output indicates a torque above a predetermined second forearm threshold value and the second sensor output indicates a torque below a predetermined first finger threshold value.

[0027] In some embodiments of any of the above, the controller is configured to operate the finger actuator to actuate the finger joint additionally based on the first sensor output.

[0028] In some embodiments of any of the above, the controller is programmed to operate the finger actuator to actuate the finger joint if the second sensor output indicates a torque above a predetermined second finger threshold value and the second sensor output indicates a torque below a predetermined third forearm threshold value.

[0029] In some embodiments of any of the above, the device further comprises one or more position sensors communicatively coupled to the controller, one or more position sensors configured to measure an angular position of the finger orthosis relative to the distal orthosis and output a position sensor signal, wherein the controller is configured to operate the finger actuator based additionally on the position sensor signal.

[0030] In some embodiments of any of the above, wherein the controller is programmed to selectively operate in a normal mode, a first grip mode and a second grip mode, wherein: in the normal mode, the finger actuator is controlled to actuate the finger joint to rotate the finger orthosis based on the sensor output; in the first grip mode the finger actuator is controlled independently of the sensor output to actuate the finger joint to rotate the finger orthosis in a first direction; and in the second grip mode the finger actuator is controlled independently of the sensor output to actuate the finger joint to rotate the finger orthosis in a second direction opposite the first direction.

[0031] In some embodiments of the above, the controller is configured to switch operation between the normal mode, the first mode and the second mode based on the sensor output.

[0032] In some embodiments of any of the above, the device comprises a user interface element communicatively coupled to the controller, and the controller is configured to switch operation between the normal mode, the first mode and the second mode based on a user input from the user interface element.

[0033] In some embodiments of any of the above, the device further comprises an or the inertial measurement unit (I MU) coupled to the distal orthosis and / or an IMU coupled to the finger orthosis, each IMU communicatively coupled to the controller, the IMU configured to measure and output one or more IMU signals indicating velocity and / or acceleration of the distal orthosis and / or finger orthosis, wherein the controller is configured to operate the finger actuator additionally based on the one or more IMU signals.

[0034] Another aspect of the present disclosure provides a powered orthotic device for providing powered assistance to a hand of a human user, the device comprising: a proximal orthosis and a distal orthosis for mounting the device to a user’s arm, the proximal orthosis configured to be mounted to a proximal location on the user’s arm and the distal orthosis configured to be mounted to a distal location on the user’s forearm and / or hand, the proximal orthosis is coupled to the distal orthosis to define an orthosis longitudinal axis extending from the proximal orthosis to the distal orthosis, such that, when the device is mounted to the user’s arm, the orthosis longitudinal axis is substantially parallel to a longitudinal axis of the user’s forearm; a finger orthosis for coupling the device to one or more fingers of the user’s hand; a finger joint coupling the finger orthosis to the distal orthosis the finger joint configured to allow the finger orthosis to pivot relative to the distal orthosis about a lateral gripping axis substantially perpendicular to the orthosis longitudinal axis; a finger actuator configured to actuate the finger joint to rotate the finger orthosis relative to the distal orthosis about the lateral gripping axis; one or more sensors configured to provide a sensor output indicating a torque transferred from the distal orthosis to the proximal orthosis about a wrist axis substantially perpendicular to the orthosis longitudinal axis, wherein the wrist axis is either a wrist flexion / extension axis oriented substantially parallel to the lateral gripping axis to correspond to the user’s wrist flexion / extension axis when the device is mounted to the user’s arm, or a wrist ulnar / radial deviation axis oriented substantially perpendicular to the lateral gripping axis to correspond to the user’s wrist ulnar / radial deviation axis when the device is mounted to the user’s arm; and a controller communicatively coupled with the one or more sensors and the finger actuator, the controller configured to operate the finger actuator to actuate the finger joint to rotate the finger orthosis based on the sensor output.

[0035] In some embodiments of the above, the one or more sensors form a sensor unit that connects the proximal orthosis to the distal orthosis such that an external torque applied to the distal orthosis is transmitted through the sensor unit.

[0036] In some embodiments of any of the above, the controller is programmed to activate the finger actuator if the sensor output indicates a torque beyond a predetermined threshold value.

[0037] In some embodiments of any of the above, wherein the controller is programmed not to activate the finger actuator if the sensor output indicates a torque that does not surpass the predetermined threshold value.

[0038] In some embodiments of any of the above, wherein the controller is configured to control the finger actuator to produce a predetermined torque or velocity to rotate the finger orthosis for a predetermined period of time when the sensor output indicates a torque beyond the predetermined threshold value.

[0039] In some embodiments of any of the above, the device further comprises one or more position sensors communicatively coupled to the controller, one or more position sensors configured to measure an angular position of the finger orthosis relative to the distal orthosis and output a position sensor signal, wherein the controller is configured to operate the finger actuator based additionally on the position sensor signal.

[0040] In some embodiments of any of the above, wherein the controller is programmed to selectively operate in a normal mode, a first grip mode and a second grip mode, wherein: in the normal mode, the finger actuator is controlled to actuate the finger joint to rotate the finger orthosis based on the sensor output; in the first grip mode the finger actuator is controlled independently of the sensor output to actuate the finger joint to rotate the finger orthosis in a first direction; and in the second grip mode the finger actuator is controlled independently of the sensor output to actuate the finger joint to rotate the finger orthosis in a second direction opposite the first direction.

[0041] In some embodiments of the above, the controller is configured to switch operation between the normal mode, the first mode and the second mode based on the sensor output.

[0042] In some embodiments of any of the above, the device comprises a user interface element communicatively coupled to the controller, and the controller is configured to switch operation between the normal mode, the first mode and the second mode based on a user input from the user interface element.

[0043] In some embodiments of any of the above, the device further comprises an or the inertial measurement unit (I MU) coupled to the distal orthosis and / or an IMU coupled to the finger orthosis, each IMU communicatively coupled to the controller, the IMU configured to measure and output one or more IMU signals indicating velocity and / or acceleration of the distal orthosis and / or finger orthosis, wherein the controller is configured to operate the finger actuator additionally based on the one or more IMU signals.

[0044] BRIEF DESCRIPTION OF DRAWINGS

[0045] One or more non-limiting examples will now be described, by way of example only, and with reference to the accompanying figures in which:

[0046] Figure 1 shows an embodiment of a powered orthotic device according to the present disclosure as part of an arm exoskeleton as worn by a user;

[0047] Figure 2 shows an embodiment of a powered orthotic device as worn by a user without the rest of the arm exoskeleton;

[0048] Figure 3 shows another embodiment of a powered orthotic device according to the present disclosure as part of an arm exoskeleton as worn by a user;

[0049] Figures 4A and 4B show top and bottom views of the powered orthotic device of Figure 2;

[0050] Figure 5 shows a front view of the powered orthotic device of Figure 2 with a partial cut-out;

[0051] Figure 6 shows a bottom view of another embodiment of a powered orthotic according to the present disclosure with a partial cut-out;

[0052] Figures 7A and 7B show perspective views of the powered orthotic device of Figure 3 as worn by a user with the forearm unit in different configurations; Figures 8A and 8B show top views of the powered orthotic device of Figure 3 as worn by a user with the gripping unit in different configurations;

[0053] Figure 9A shows a perspective view of the powered orthotic device of Figure 2;

[0054] Figure 9B shows another partial perspective view of the powered orthotic device of Figure 2 with a partial cut-out;

[0055] Figure 10 shows a perspective view of another embodiment of a powered orthotic device according to the present disclosure;

[0056] Figure 11 is a graph demonstrating control of the gripping unit based on torque / moment thresholds;

[0057] Figure 12 is a graph demonstrating control of the device based on a user’s intent; and

[0058] Figure 13 is a graph demonstrating control of the device based on a user’s intent;

[0059] Figure 14 shows a side view of another embodiment of a powered orthotic device according to the present disclosure; and

[0060] Figure 15 shows a side view of another embodiment of a powered orthotic device according to the present disclosure.

[0061] DETAILED DESCRIPTION

[0062] In accordance with the present disclosure, Figures 1 to 12 show embodiments of a powered orthotic device 10 for providing powered assistance to a user’s forearm and hand movements to support the user in the functional activities of daily living, such as dressing, cooking and cleaning. The device 10 may be particularly beneficial to users with arm and hand motor impairments, for example as a result of a medical condition such as a stroke or a brachial plexus injury. However, the device 10 may also be used to augment the arm and grip strength and mobility of a user who does not have a perceptible motor impairment.

[0063] The device 10 provides powered assistance to forearm pronation / supination and / or powered gripping assistance for opening and closing the grip of the user. Forearm pronation / supination refers to the movement of rotating the forearm about its longitudinal axis. The powered movements of the device 10 are controlled using measurement of the interaction torques / forces between the device 10 and the user.

[0064] When the device 10 registers that the user pronates their forearm, the device 10 provides powered assistance to pronate the forearm of the user. When the device 10 register that the user supinates their forearm, the device 10 provides powered assistance to supinate the forearm of the user.

[0065] For many individuals with an arm impairment, such as stroke survivors, moving their joints through their full range of motion is difficult. They might be able to produce a movement impulse, but not able to produce a continuous movement through the whole range of motion. The device 10 can use a force or torque impulse generated by the user to recognize an intention to carry out a movement, and then the device 10 can produce an assistive torque to move the joint through the whole range of motion to help complete the intended action. For example, if the user can slightly pronate their forearm from a neutral position, this force impulse can be utilized by the device 10 to move their forearm all the way into a functional pronated position.

[0066] Many individuals with an arm impairment, such as stroke survivors, retain some sort of voluntary force in wrist flexion / extension, and can thus use this force as a control input for the powered gripping assistance of the device 10. When the device 10 registers that the user flexes their wrist, the device 10 provides powered assistance to close the fingers for a grip. When the device 10 registers that the user is extending their wrist, the device 10 provides powered assistance to open the grip of the user.

[0067] With reference to Figures 1 to 12, embodiments of the device 10 includes a powered forearm unit 12 for powered assistance to forearm pronation / supination and / or a powered gripping unit 14 for powered gripping assistance. The device 10 comprises a power source (not shown), such as one or more batteries. In the embodiments of Figures 1 to 8, 11 and 12, the device 10 includes both the forearm unit 12 and the gripping unit 14, but in other embodiments, as shown in Figures 14 and 15, the device may provide only one of the forearm unit 12 and the gripping unit 14, as discussed further below. As shown in Figure 1 , the device 10 may form part of a whole arm exoskeleton 2 that also includes an upper arm portion 4, a shoulder joint 5 and a shoulder portion 6, with the forearm unit 12 joined to the upper arm portion 4 at a pivotable or fixed elbow joint 8. As shown in Figure 3, the device 10 may also form part of an arm exoskeleton 3 that includes an upper arm portion 4, with the forearm unit 12 joined to the upper arm portion 4 at a pivotable or fixed elbow joint 8. In embodiments of the device 10 that just include the gripping unit 14, a supportive passive forearm orthosis may take the place of the forearm unit 14 to link the gripping unit 12 to the upper arm portion 4.

[0068] The forearm unit 12 comprises at least a proximal orthosis 16 and a distal orthosis 18 for mounting the device 10 to a user’s arm. The gripping unit 14 comprises the distal orthosis 18 and at least one finger orthosis 20 for coupling the device to one or more fingers of the user’s hand. Herein, “distal” refers to the direction along the user’s arm towards their hand when the device 10 is worn, and “proximal” refer to the direction along the user’s arm towards their shoulder / torso when the device 10 is worn. The proximal orthosis 16 may be mounted on the user’s arm at a location above, at or below the user’s elbow. In the embodiments depicted in Figures 3 and 7A to 8B, the proximal orthosis 16 is placed above the elbow, while in the embodiment depicted in Figures 1 and 2, the proximal orthosis 16 is mounted below the elbow, on the user’s forearm.

[0069] With particular reference to Figure 4, the proximal orthosis 16 is rotationally coupled to the distal orthosis 18 at an off-axis forearm joint 22. In the depicted embodiments, the proximal orthosis 16 includes a rigid strut 17 between the forearm joint 22 and a cuff 19 for mounting to the forearm. The forearm joint 22 allows the distal orthosis 18 to rotate relative to the proximal orthosis 16 about a longitudinal rotation axis 26 that approximately corresponds to the rotational axis of pronation and supination motion of the user’s forearm when the user is wearing the device 10. The forearm joint 22 is a remote centre of motion joint and so the longitudinal rotation axis 26 is positioned laterally distal to the device 10 and orthosis longitudinal axis 24. The longitudinal rotation axis 26 may be substantially parallel to the orthosis longitudinal axis 24 defined between the proximal orthosis 16 to the distal orthosis 18.

[0070] The forearm joint 22 comprises a forearm actuator 28 to provide powered rotation to the distal orthosis 18 about the longitudinal rotation axis 26 relative to the proximal orthosis 16. When the user is wearing the device 10, the forearm actuator 28 is thus operative to produce pronation and supination rotation of the user’s forearm. The range of motion of the forearm joint 22 produced by the forearm actuator 28 may be in the range of about -90° to about +90° about the longitudinal rotation axis 26 in order provide a full range of pronation / supination of the user’s forearm. The range of motion may also be limited to a smaller rotational range.

[0071] With additional reference to Figures 5 and 6, the forearm actuator 28 has an output 29 that is rigidly connected to the distal orthosis 18. In the depicted embodiments, the forearm joint 22 comprises an arc sliding element 23 rigidly fastened to the forearm actuator output 29 and an arc carrier 35 rigidly fastened to the proximal orthosis 16. The arc sliding element 23 and arc carrier 35 can slide with respect to each other making an off-axis rotation about the longitudinal rotation axis 26. The forearm actuator 28 produces a torque output via a forearm electric motor 33 rigidly fastened to the arc carrier 35. The forearm electric motor 33 drives a gear unit 25 that engages with the teeth of an arc gear 27 rigidly fastened to the arc sliding element 23 and forearm actuator output 29.

[0072] Rotation of the distal orthosis 18 via the forearm joint 22 by the forearm actuator 28, as demonstrated in Figs 7A and 7B, is controlled by a controller or microprocessor 30 on the basis of a first sensor output from a sensor unit 31 comprising one or more sensors 32, for example a torque sensor, a moment sensor and / or a force sensor, communicatively coupled to the controller 30. In some embodiments, the controller 30 may comprise more than one controller communicatively coupled to each other, such as a network of controllers. The first sensor output indicates an applied supination / pronation torque transferred between the distal orthosis 18 and the proximal orthosis 16 when the user initiates a forearm supination / pronation movement. In some examples, the one or more sensors 32 may directly measure torque / moment / force and provide the measurement to the controller 30 as the first sensor output, or the controller 30 may be programmed to derive the torque / moment / force based on the first sensor output from the one or more sensors 32.

[0073] The sensor unit 31 rigidly connects the forearm actuator output 29 to the distal orthosis 18 such that all interaction torques / moments / forces between the distal orthosis 18 and the user or environment are transferred through the sensor unit 31. In some embodiments, the one or more sensors 32 comprise a torque / moment / force sensor capable of measuring the torque / moment / force transferred through the sensor unit 31 in at least one direction. In one embodiment, the one or more sensors 32 may be based on strain gauge technology. Strain gauges 32 are placed on one or more surfaces of the sensor unit 31 , and are capable of registering deformations in the material as forces / torques / moments are transferred through the sensor unit 31. By placing the strain gauges 32 in different configurations on the sensor unit 31 , it is possible to isolate forces / moments / torques in different directions. In one embodiment, the strain gauges 32 is configured to isolate the measurement of torques that are transferred along the sensor longitudinal axis 60. The sensor longitudinal axis 60 is approximately parallel to the longitudinal rotation axis 26. In this embodiment, the sensor unit 31 is configured to output a signal representing the user applying a pronation / supination torque.

[0074] In response to detecting an applied torque due to pronation / supination, the controller 30 operates the forearm actuator 28 to produce an assistive torque in the forearm joint 22 to rotate the distal orthosis 18 relative to the proximal orthosis 16. The assistive torque from the forearm actuator 28 supplements the applied torque generated by the user and thus aids the user in completing the intended pronating / supination movement.

[0075] The controller 30 may be configured to control the forearm actuator 28 based on the first sensor output on a directional threshold basis, for example based on threshold torque values. For example, the forearm actuator 28 may be commanded to rotate the distal orthosis 18 and user’s forearm in the direction of pronation when the first sensor output is above a threshold value in the pronation direction (e.g., a positive torque value), and the forearm actuator 28 may be commanded to rotate the distal orthosis 18 and the user’s forearm in the supination direction when the first sensor output is above a threshold value in the supination direction (e.g., a negative torque value). If the first sensor output is a torque value, the threshold values would also be torque values. This means that the user can get powered assistance from the device 10 in carrying out forearm pronation / supination by starting to attempt the pronation / supination movement.

[0076] The controller 30 may be programmed to control the forearm actuator 28 to produce a predetermined fixed amount of assistive torque for a predetermined period of time when the applied torque is determined to be above a threshold value. Alternatively or additionally, the controller 30 may be programmed with more than one threshold value and to apply different level of assistive torque depending on the surpassed threshold. For example, if the applied torque is determined to be above a first threshold, a first torque is generated by the forearm actuator 28 for a first period of time, then, if the applied torque is determined to be above a second, higher threshold, a second torque is generated by the forearm actuator 28 for a second period of time. The second torque may be higher or lower than the first torque, and the first period of time may be longer or shorter than the second period of time. More thresholds, torque and periods of time may also be included. In other examples, the assistive torque produced by the forearm actuator 28 may be proportional to the determined applied torque. This proportionality control may be combined with a threshold-based control.

[0077] With regard to the gripping unit 14, referring particularly to Figures 4, 6, and 8A to 10, the finger orthosis 20 is pivotally coupled to the distal orthosis 18 by a finger joint 34. The finger joint 34 allows the finger orthosis 20 to rotate relative to the distal orthosis 18 about a lateral gripping axis 36, or finger flexion axis 36. Through the mounting of the distal orthosis 18 on the user’s forearm / hand and the finger orthosis 20 on one or more fingers of the user, this rotation about the lateral gripping axis 36 produces finger flexion and extension to open and close the hand for gripping and releasing actions, as demonstrated in Figs 8A and 8B. The lateral gripping axis 36 may be approximately perpendicular to the longitudinal rotation axis 26 for forearm pronation / supination movement.

[0078] The finger joint 34 comprises a finger actuator 38 to provide powered rotation to the finger orthosis 20 about the lateral gripping axis 36 relative to the distal orthosis 18. When the user is wearing the device 10, the finger actuator 38 is thus operative to produce flexion and extension of the user’s fingers. The range of motion of the finger joint 34 produced by the finger actuator 38 may be in the range of about 0° (corresponding to straight fingers) to about 90° (corresponding to closed fingers) about the lateral gripping axis 36 in order provide a full range of flexion / extension of the user’s fingers for gripping and releasing actions. In some embodiments (not shown), the finger orthosis 20 can be configured to support the thumb of the user, where the finger joint 34 and finger actuator 38 are configured to provide rotation of the thumb towards the other fingers of the user.

[0079] In some embodiments, as shown in Figures 9A and 9B, the finger actuator 38 comprises an electric finger motor 41 rigidly connected to the distal orthosis 18 and configured to transfer its output power to a finger gear unit 43 that transfers the rotational power to the finger orthosis 20 about the finger joint 34. In addition or alternatively to a geared electric motor 41 , the finger actuator 38 may be configured in any other known manner, e.g., a pneumatic actuator, belt drive, cable drive, hydraulic actuator.

[0080] Rotation of the finger orthosis 20 via the finger joint 34 by the finger actuator 38 is controlled by controller / microprocessor 30 (or alternatively by a separate controller) on the basis of a second sensor output from one or more wrist sensors 42, for example a torque sensor, a moment sensor and / or a force sensor, communicatively coupled to the controller 30. The second sensor output indicates a torque generated by the user in their wrist about a wrist axis 50, 51 , as indicated in Figures 4A and 4B. The wrist axis may be a wrist flexion / extension axis 50 or a wrist ulnar / radial deviation axis 51 . With reference to Figure 4B, the wrist flexion / extension axis 50 is approximately perpendicular to the longitudinal rotation axis 26 and approximately parallel to the lateral gripping axis 36. The wrist flexion axis 50 may approximately correspond to or be parallel to the user’s wrist flexion / extension axis when the device 10 is worn. With reference to Figure 4A. the wrist deviation axis 51 is approximately perpendicular to both the longitudinal rotation axis 26 and the lateral gripping axis 36. The wrist deviation axis 51 may approximately correspond to or be parallel to the user’s wrist ulnar / radial deviation axis when the device 10 is worn. However, the measurement point of the wrist torque may be moved anywhere along the orthosis longitudinal axis 24. The one or more wrist sensors 42 thus determine torque generated by the user in their wrist in flexion / extension motion or radial / ulnar deviation motion. The following description uses the example of determining wrist flexion / extension torque about the wrist flexion axis 50, but may equally be applied to wrist ulnar / radial deviation torque about the wrist deviation axis 51. In some examples, the one or more wrist sensors 42 may directly measure torque / moment / force and provide the measurement to the controller 30 as the second sensor output, or the controller 30 may be programmed to derive the torque / moment / force based on the second sensor output from the one or more wrist sensors 42.

[0081] The one or more wrist sensors 42 may use strain gauge technology, as discussed above for the one or more sensors 32. In the embodiments shown in Figures 4 and 6, the one or more wrist sensors 42 are provided as part of sensor unit 31 and indicate the applied wrist flexion / extension torque transferred to the sensor unit 31 through the distal orthosis 18. As the wrist flexion / extension torque and the forearm pronation / supination torques are applied in different directions, about different axes, the sensor unit 31 can include both the sensor(s) 32 for measuring the pronation / supination torque and the wrist sensor(s) 42 for measuring the wrist flexion / extension torque. By placing the sensors 32, 42, such as strain gauges 32, 42, in different configurations on the sensor unit 31 , it is possible to isolate torques applied in different directions.

[0082] Therefore, in some embodiments, the sensor unit 31 , comprising sensor(s) 32 and wrist sensor(s) 42, is configured to isolate the measurement of torques that are transferred through the sensor unit 31 about the wrist flexion axis 50 and to isolate the measurement of torques that are transferred along the sensor longitudinal axis 60. In this embodiment, the sensor is configured to output a signal representing the user applying a wrist flexion / extension torque. In this embodiment, the sensor unit 31 is configured to output at least two sensor output signals: a first sensor output signal representing the user applying a pronation / supination torque; and a second sensor output signal representing the user applying a wrist flexion / extension torque.

[0083] In embodiments, the sensor unit 31 may comprise a bidirectional bending moment sensor that can measure the bending moment / torque transferred through the sensor unit 31 about two axes: the wrist flexion axis 50 and the longitudinal rotation axis 26. The sensor unit 31 provides the first sensor output indicating the transferred bending moment about the longitudinal rotation axis 26 and the second sensor output indicating the transferred bending moment about the wrist flexion axis 50, for example using strain gauge technology.

[0084] With reference to Figure 10, in other embodiments, the one or more wrist sensors 42 may be provided separately to the one or more sensors 32, rigidly between the distal orthosis 18 and the proximal orthosis 16. The wrist sensor(s) 42, such as strain gauges 42, are configured to isolate the measurement of torques that are transferred through the sensor(s) 42 about the wrist flexion axis 50. In this embodiment, the wrist sensor(s) 42 is configured to output a signal representing the user applying a wrist flexion / extension torque.

[0085] In some embodiments, the distal orthosis 18 is configured to hold at least a proximal portion of the user’s hand firmly in place relative to the distal orthosis 18 and the one or more wrist sensors 42 so that the generation of force in the wrist flexion / extension is isometric. This makes generating a force from wrist flexion / extension as a control signal even possible for users with weakened arm muscles who may struggle to control the wrist flexion / extension in “free air”. In isometric contractions, the muscle generates force without changing its length (e.g., pushing against a wall), as opposed to isotonic contractions, in which the muscle changes length while generating force (e.g. lifting a dumbbell during a bicep curl).

[0086] In response to detecting an applied torque due to wrist flexion / extension, the controller 30 operates the finger actuator 38 to produce an assistive torque in the finger joint 34 to rotate the finger orthosis 20 relative to the distal orthosis 18. The device 10 thus uses the user’s wrist flexion / extension as a signal to provide assistance to a gripping motion of the fingers.

[0087] With reference to Figure 11 , the controller 30 may be configured to control the finger actuator 38 based on the second sensor output on a directional threshold basis, for example based on threshold torque values. Figure 13 shows how the user’s applied moment / torque, Mwrist, in extension and flexion gives rise to a grip close / open action when Mwrist is above / below a threshold. For example, the finger actuator 38 may be commanded to rotate the finger orthosis 20 to close the fingers / grip when the second sensor output is above a threshold value in the flexion direction (e.g., a positive torque value), and the finger actuator 38 may be commanded to rotate the finger orthosis 20 to open the fingers / grip when the second sensor output is above a threshold value in the extension direction (e.g., a negative torque value). This means that the user can open their grip by trying to extend their wrist and close their hand by trying to flex their wrist. It is also possible to switch direction of how a sensor input causes an actuator command so that a wrist flexion commands an opening of the hand, and a wrist extension commands a closing of the hand.

[0088] The controller 30 may be programmed to control the finger actuator 38 to produce a predetermined fixed amount of assistive torque for a predetermined period of time when the applied torque is determined to be above a threshold value. Alternatively or additionally, the controller 30 may be programmed with more than one threshold value and to apply different level of assistive torque depending on the surpassed threshold. For example, if the applied torque is determined to be above a first threshold, a first torque is generated by the finger actuator 38 for a first period of time, then, if the applied torque is determine to be above a second, higher threshold, a second torque is generated by the finger actuator 38 for a second period of time. The second torque may be higher or lower than the first torque, and the first period of time may be longer or shorter than the second period of time. More thresholds, torque and periods of time may also be included. In other examples, the assistive torque produced by the finger actuator 38 may be proportional to the determined applied torque. This proportionality control may be combined with a threshold-based control.

[0089] As shown in Figure 9A, in some embodiments, the gripping unit 14 may include one or more position sensors 44 measuring the angular position of the finger orthosis 20 relative to the distal orthosis 18 about the finger flexion axis 36. The one or more position sensors 44, communicatively coupled to the controller 30, output a signal to the controller 30 that indicates the measured angular position. This position sensor signal may be used by the controller 30, in combination with the first and / or second sensor output from the one or more sensors 32 and / or one or more wrist sensors 42 to command the finger actuator 38. For example, the position sensor signal may be used to stop movement of the finger actuator 38 when the finger joint 34 reaches a safe or useful end of range of motion. The one or more position sensor 44 may be used in a feedback loop to control the speed of the actuated movement about the finger joint 34. The one or more position sensors 44 may be mounted on the distal orthosis 18 and / or the finger orthosis 20.

[0090] As discussed above, in some embodiments the one or more sensors 32 for determining applied pronation / supination torque and the one or more wrist sensors 42 for determining applied wrist flexion / extension torque are provided as part of the sensor unit 31 , which rigidly couples the forearm joint 22 to the distal orthosis 18. The sensor unit 31 generates a first sensor output when a differential torque / force is applied between the distal orthosis 18 and the proximal orthosis 16 about the longitudinal rotation axis 26. This torque / force is applied by the user when supinating or pronating their forearm. The sensor unit 31 generates a second sensor output when a differential torque / force is applied to the distal orthosis 18 about the wrist flexion axis 50. This torque / force is applied by the user when flexing / extending their wrist joint.

[0091] The sensor unit 31 is communicatively coupled to the controller 30 to provide the first sensor output and the second sensor output to the controller 30. The controller 30 is configured to command movement of the forearm actuator 28 based on the first sensor output and movement of the finger actuator 38 based on the second sensor output.

[0092] In some embodiments, the controller 30 may be programmed to automatically calibrate the first and / or second sensor output from sensor unit 31. One such calibration scheme by the controller 30 might include calibrating the signal(s) towards zero with a constant or varying rate. This “attrition rate” might be especially useful for users of the device 10 who have contractions or spasticity in their arm that involuntarily exerts a torque on the distal orthosis 18 compared to the proximal orthosis 16. This involuntary torque can, for example, come from the user’s arm always trying slightly to pronate with a constant or close-to-constant torque. The attrition rate will allow the torque signal about the longitudinal rotation axis 26 to slowly be calibrated to the “resting torque” of the user, and afterwards be usable as a control signal.

[0093] In some embodiments, as demonstrated by the graph in Figure 11 , the movement of the finger actuator 38 may be based only on the second sensor output. Additionally, the movement of the forearm actuator 28 may be based only upon the first sensor output. This allows both the powered pronation / supination assistance and the powered gripping assistance to be provided independently and simultaneously.

[0094] In other embodiments, as demonstrated by the graphs in Figures 12 and 13, both the first sensor output and the second sensor output can be utilized to control both the forearm actuator 28 and the finger actuator 38. To ensure that the user does not need to perfectly separate wrist flexion / extension and forearm supination / pronation to isolate one movement, the two different sensor outputs can be mapped onto zones of the user’s intent, as demonstrated in Figures 12 and 13.

[0095] For example, if the user is flexing their wrist, while managing to keep their forearm pronation / supination activation low / absent, which corresponds to area GC in Figure 12, the user can indicate a “grip close” intent through the sensor outputs and the controller 30 will cause the finger actuator 38 to activate to close the user’s grip. However, if the user is both pronating their forearm and flexing their wrist at the same time, the combination of the two sensor outputs will put the user in the “no intent” (Nl) zone, where the controller 30 would not issue any actuator command. Thus, in such embodiments, only one actuator command will be issued at a time.

[0096] Figures 12 and 13 demonstrate different ways of using the combinations of sensor outputs indicating the user’s wrist flexion / extension and forearm pronation / supination intents to activate the forearm actuator 28 in the FP and FS areas of the graphs and the finger actuator 38 in the GC and GO areas of the graphs. Figure 13 shows that the forearm actuator 28 would be activated for assistive pronation / supination if the pronation / supination moment is high enough (i.e., above a predetermined moment threshold), regardless of the wrist flexion / extension moment. Similarly, the finger actuator 38 would be activated for assistive grip opening / closing if the wrist flexion / extension moment is high enough (i.e., above a predetermined moment threshold), regardless of the pronation / supination moment. Therefore, as can be seen from the GC + FP, GC + FS, GO + FP and GO + FS areas of Figure 13, if both the wrist flexion / extension and forearm pronation / supination moments are high enough at the same time, both the forearm actuator 28 and the finger actuator 38 are activated simultaneously. If either moment is below the threshold, no intent is registered and the corresponding actuator 28, 38 is not activated.

[0097] Combining the sensor outputs thus provides more control over the assistance provided by the forearm unit 12 and the gripping unit 14 and may make it easier for the user to exert more precise control over the assisted movements of their forearm and hand.

[0098] With reference to Figure 14, in some embodiments, the device 10 comprises the powered gripping unit 14 without the powered forearm unit 12. In such embodiments, a forearm joint 22’ may allow free rotation of the distal orthosis 18 relative to the proximal orthosis 16 about the longitudinal rotation axis 26, or the forearm joint 22’ may be a rigid coupling between the distal orthosis 18 and proximal orthosis 16. The forearm joint 22’ may additionally or alternatively be a mechanically adjustable coupling between the distal orthosis 18 and the proximal orthosis 16 that allows the user to manually adjust the rotational position between discrete locked positions. As shown in Figure 14, the forearm joint 22’ does not comprise an actuator. The distal orthosis 18 is coupled to the forearm joint 22’ by the sensor unit 31 , which comprises the one or more wrist sensors 42 for determining applied wrist flexion / extension torque about the wrist flexion axis 50. The powered gripping unit 14 can operate in the same way as described above for the embodiments with both the gripping unit 14 and the forearm unit 12.

[0099] With reference to Figure 15, in other embodiments, the device 10 comprises the powered forearm unit 12 without the powered gripping unit 14. The distal orthosis 18 may still provide support to the user’s hand. The distal orthosis 18 is coupled to the forearm joint 22 by the sensor unit 31 , which comprises the one or more sensors 32 for determining applied pronation / supination torque about the longitudinal rotation axis 26. In some embodiments, as shown in Figure 9A, the device 10 includes an inertial measurement unit (IMU) 62 rigidly mounted to the distal orthosis 18, or to any other part rigidly connected to the distal orthosis 18, and / or to the finger orthosis 20. The IMU 62 measures 3-axis velocities and 3-axis acceleration of the distal orthosis 18 or finger orthosis 20, and is communicatively coupled with the controller 30. The accelerations and velocities communicated from the IMU 62 to the controller 30 may be utilized by the controller 30, together with the information from the first and / or second sensor output from the one or more sensors 32 and / or wrist sensors 42, to command the movements of the actuators 28, 38. For example, outputs from the IMU 62 may be utilized by the controller 30 to infer the orientation of the hand in 3D space by, e.g., estimating the direction of the gravity vector. This information can further be utilized to estimate the weight of the hand of the user, and any weight of objects being held by the user, which will influence the first and second output signals from the sensors 32, 42. For example if the hand of the user is placed in a manner which makes the wrist flexion axis 50 sufficiently orthogonal with the gravity vector, the weight of the user’s hand / arm resting in the distal orthosis 18 will create a torque about the wrist flexion axis 50. This torque will result in a contribution to the second sensor output signal not originating from a voluntary torque about the wrist flexion axis 50. By knowing the orientation of the distal orthosis 18, this torque contribution can be estimated and accounted for.

[0100] In some embodiments, the movements of the forearm actuator 28 and / or finger actuator 38 may be commanded to run for a minimum time when a user intent is registered. This minimum time allows the user to utilize a force impulse to control a prolonged movement of the actuator 28, 38. The minimum time can be pre-set and tailored to meet the needs of the specific user. For example, for a user with very limited motor control, the minimum runtime for the forearm actuator 28 may be set to be long enough for a pronation impulse above a threshold in a fully supinated position to lead to a movement all the way to a fully pronated position. For a user with more motor control, the minimum time may be set such that a movement impulse will yield a movement of a fraction of the full range of motion, e.g., one third of the range of motion. For a user with even better motor control, the minimum time may be set to be very short, or to zero, such that the control of the movement is continuous or close to continuous. If a position measurement of the joints us available, the minimum time may also be implemented as a minimum distance or angular distance travelled.

[0101] With reference to Figure 6, in some embodiments, an external communication unit or device 48 communicatively coupled to the controller 30 can be used to adjust settings on the device 10. The external communication unit 48 may be communicatively coupled to the controller 30 via a wired connection 52 and / or via a wireless connection 54. In some examples, the external communication unit 48 may be configured to change parameters related to the recognition of the user’s movement intent including, but not limited to, torque threshold and minimum movement time. The external communication unit 48 may also be configured to change parameters relating to the movement of the actuators 28, 38, including but not limited to, actuator speed, joint range of motion and maximum torque. The external communication unit 48 may also be configured to change movement modes of the device 10. The external communication unit may also directly command movements of the actuators 28, 38 through the controller 30. The external communication unit 48 may be in the form of a mobile application (e.g., on a smartphone or tablet) in wired or wireless communication with the controller 30, a computer program on an external device in wired or wireless) communication with the controller 30, or any other known communication unit.

[0102] In some embodiments, the forearm actuator 28 and / or finger actuator 38 may be operated in different modes of operation depending on the amount and / or type of assistance needed by the user. In a normal operation mode of the device 10, the forearm actuator 28 and / or the finger actuator 38 is controlled by the controller 30 in response to the first and / or second sensor output signal from the sensor unit 31. However, in certain situations, a different method for controlling the actuators might be preferred by the user, and so the device 10 can be put into different operation modes to suit different situations or intentions by the user.

[0103] For example, if the user wishes to grasp an object and hold on to that object for an extended amount of time, the user might not be able to, or wish to, precisely control their flexion / extension torque in the wrist for that extended amount of time. The controller 30 can then put the device 10 into a specific operation mode to assist the extended grasping, for example ‘grasp mode’.

[0104] In grasp mode, the controller 30 will attempt to keep the grasp of the user closed, independently of the sensor signals from the sensor unit 31. The controller 30 may put the device 10 into grasp mode from an internal trigger based on the information from the first and / or second signals from the sensor unit 31 , from signals from the position sensor 44, and / or from signals from the IMU 62. The controller 30 may also put the device 10 into grasp mode from the interaction with a user interface element 46 on the device 10, e.g., a button or switch, or by the external communication unit 48, as shown in Figure 6. In grasp mode, the controller 30 may attempt to keep the grasp closed by applying a closing torque, by keeping the finger actuator 38 at a constant position, by always trying to close the grip further, or by other known means of controlling an actuator. The controller 30 may exit grasp mode and resume normal operation of the device 10 through an internal trigger based on the first and / or second sensor signal from the sensor unit 31 , from the interaction with the user interface element 46 on the device 10, or from the external communication unit 48.

[0105] In another example situation, the user might want assistance to keep their hand / grip open for an extended period of time. This might be especially useful for individuals that have a clenched hand, i.e., a hand that involuntarily tries to close itself. Similarly to a grasp mode, the controller 30 may also put the device 10 into an ‘open mode’, where the controller 30 constantly tries to open the finger actuator 38, independently of the sensor signals from the sensor unit 31. The switching on and off of the open mode may be executed similarly to the grasp mode, e.g., through a user interface element 46 on the device 10, e.g., a button or switch, or the external communication unit 48.

[0106] A powered orthotic device 10 according to the present disclosure provides a user with a weakened arm with motorised assistance to their arm and hand movements. The user can control the assistance provided by the device by applying torque with their forearm and hand to register their movement intent, which is picked up by sensors. The forearm pronation / supination assistance is provided when the sensors register that the user is applying a pronation / supination torque, which provides easy and intuitive control of the device. The grasping and releasing torque for gripping motions of the hand is provided when the sensors register movement of the user’s wrist, whether through a flexion / extension torque, or an ulnar / radial deviation torque. The user’s wrist torque is used as an analogue to register intent to control the fingers. This can be beneficial compared to directly measuring finger torque, because the wrist may be stronger than finger joints and some users may have more control over their wrist than their fingers, for example users with a clenched hand. Using torque / moment / force sensors to determine a user’s intent in their forearm and wrist motions allows the powered assistance to be provided without using EMG electrodes or fingertip pressure sensors, for example. A powered orthotic device 10 according to the present disclosure may therefore be easier for a user to mount and operate the device 10 accurately and independently.

Claims

CLAIMS1. A powered orthotic device (10) for providing powered assistance to a forearm of a human user, the device (10) comprising: a proximal orthosis (16) and a distal orthosis (18) for mounting the device (10) to a user’s arm, the proximal orthosis (16) configured to be mounted at a proximal position on the user’s arm and the distal orthosis (18) configured to be mounted at a distal position on the user’s forearm and / or hand; a forearm joint (22) coupling the proximal orthosis (16) to the distal orthosis (18) to define an orthosis longitudinal axis (24) extending from the proximal orthosis (16) to the distal orthosis (18), such that, when the device (10) is mounted to the user’s arm, the orthosis longitudinal axis (24) is substantially parallel to a longitudinal axis of the user’s forearm, wherein the forearm joint (22) is configured as a remote centre of motion joint to allow the distal orthosis (18) to rotate relative to the proximal orthosis (16) about a longitudinal rotation axis (26) positioned laterally distal to the device (10), the longitudinal rotation axis (26) substantially parallel to the orthosis longitudinal axis (24); a forearm actuator (28) configured to actuate the forearm joint (22) to rotate the distal orthosis (18) relative to the proximal orthosis (16) about the longitudinal rotation axis (26); a sensor unit (31) comprising one or more sensors (32) configured to provide a first sensor output indicating one or more torques transferred from the distal orthosis (18) to the proximal orthosis (16) through the forearm joint (22); and a controller (30) communicatively coupled with the sensor unit (31) and the forearm actuator (28), the controller (30) is configured to operate the forearm actuator (28) to actuate the forearm joint (22) to rotate the distal orthosis (18) based on the first sensor output.

2. The powered orthotic device of claim 1 , wherein the forearm joint (22) is configured such that, when the device is in use and mounted to a user’s arm, the distal orthosis (18) rotates relative to the proximal orthosis (16) about the longitudinal rotation axis (26) in response to the user’s forearm exerts a force for a pronation or supination.

3. The powered orthotic device of claim 2, wherein the one or more sensors (32) are configured to, in use, provide the first sensor output indicating one or more torques transferred from the distal orthosis (18) to the proximal orthosis (16) through the forearm joint (22) due to the user’s forearm exerting force for the pronation or supination.

4. The powered orthotic device of claim 3, wherein the controller (30) is configured to operate the forearm actuator (28) such that, in use, the forearm actuator (28) actuates the forearm joint (22) to rotate the distal orthosis (18) based on the first sensor output to assist the user in performing the pronation or supination.

5. The powered orthotic device of any preceding claim, wherein the forearm actuator (28) comprises a forearm actuator output (29) rigidly coupled to the sensor unit (31), and the distal orthosis (18) is rigidly coupled to the forearm joint (22) via the sensor unit (31), such that an external torque applied to the distal orthosis (18) and a torque produced by the forearm actuator (28) at the forearm actuator output (29) are transmitted through the sensor unit (31).

6. The powered orthotic device of any preceding claim, wherein the controller (30) is programmed to activate the forearm actuator (28) if the first sensor output indicates a torque or velocity beyond a predetermined first forearm threshold value.

7. The powered orthotic device of claim 6, wherein the controller (30) is programmed not to activate the forearm actuator (28) if the first sensor output indicates a torque that does not surpass the predetermined first forearm threshold value.

8. The powered orthotic device of claim 6 or 7, wherein the controller (30) is configured to control the forearm actuator (28) to produce a predetermined torque or velocity to rotate the distal orthosis (18) for a predetermined period of time when the first sensor output indicates a torque beyond the predetermined first forearm threshold value.

9. The powered orthotic device of any preceding claim, further comprising an inertial measurement unit (IMU) (62) coupled to the distal orthosis (18) and communicatively coupled to the controller (30), the IMU (62) configured to measure and output one or more IMU signals indicating velocity and acceleration of the distal orthosis (18), wherein the controller (30) is configured to operate the forearm actuator (28) additionally based on the one or more IMU signals.

10. The powered orthotic device of any preceding claim, further comprising: a finger orthosis (20) for coupling the device (10) to one or more fingers of the user’s hand, the finger orthosis (20) coupled to the distal orthosis (18) at a finger joint (34), the finger joint (34) configured to allow the finger orthosis (20) to pivot relative to the distal orthosis (18) about a lateral gripping axis (36) substantially perpendicular to the orthosis longitudinal axis (24); and a finger actuator (38) configured to actuate the finger joint (34) to rotate the finger orthosis (20) relative to the distal orthosis (18) about the lateral gripping axis (36).

11. The powered orthotic device of claim 10, wherein: the sensor unit (31) comprises one or more wrist sensors (42) configured to provide a second sensor output indicating a torque transferred from the distal orthosis (18) to the proximal orthosis (16) through the forearm joint (22; 22’) about a wrist axis (50; 51) substantially perpendicular to the orthosis longitudinal axis (24), wherein the wrist axis (50; 51) is either a wrist flexion / extension axis(50) oriented substantially parallel to the lateral gripping axis (36) to correspond to the user’s wrist flexion / extension axis when the device (10) is mounted to the user’s arm, or a wrist ulnar / radial deviation axis (51) oriented substantially perpendicular to the lateral gripping axis (36) to correspond to the user’s wrist ulnar / radial deviation axis when the device (10) is mounted to the user’s arm; and the controller (30) is communicatively coupled with the finger actuator (38), the controller (30) configured to operate the finger actuator (38) to actuate the finger joint (34) based on the second sensor output.

12. The powered orthotic device of claim 11 , wherein the controller (30) is configured to operate the forearm actuator (28) to actuate the forearm joint (22) to rotate the distal orthosis (18) additionally based on the second sensor output.

13. The powered orthotic device of claim 12, wherein the controller (30) is programmed to operate the forearm actuator (28) to actuate the forearm joint (22) if the first sensor output indicates a torque above a predetermined second forearm threshold value and the second sensor output indicates a torque below a predetermined first finger threshold value.

14. The powered orthotic device of claim 11 , 12 or 13, wherein the controller (30) is configured to operate the finger actuator (38) to actuate the finger joint (34) additionally based on the first sensor output.

15. The powered orthotic device of claim 14, wherein the controller (30) is programmed to operate the finger actuator (38) to actuate the finger joint (34) if the second sensor output indicates a torque above a predetermined second finger threshold value and the second sensor output indicates a torque below a predetermined third forearm threshold value.

16. A powered orthotic device (10) for providing powered assistance to a hand of a human user, the device (10) comprising: a proximal orthosis (16) and a distal orthosis (18) for mounting the device (10) to a user’s arm, the proximal orthosis (16) configured to be mounted to a proximal location on the user’s arm and the distal orthosis (18) configured to be mounted to a distal location on the user’s forearm and / or hand, the proximal orthosis (16) is coupled to the distal orthosis (18) to define an orthosis longitudinal axis (24) extending from the proximal orthosis (16) to the distal orthosis (18), such that, when the device (10) is mounted to the user’s arm, the orthosis longitudinal axis (24) is substantially parallel to a longitudinal axis of the user’s forearm; a finger orthosis (20) for coupling the device (10) to one or more fingers of the user’s hand;a finger joint (34) coupling the finger orthosis (20) to the distal orthosis (18), the finger joint (34) configured to allow the finger orthosis (20) to pivot relative to the distal orthosis (18) about a lateral gripping axis (36) substantially perpendicular to the orthosis longitudinal axis (24); a finger actuator (38) configured to actuate the finger joint (34) to rotate the finger orthosis (20) relative to the distal orthosis (18) about the lateral gripping axis (36); one or more sensors (42) configured to provide a sensor output indicating a torque transferred from the distal orthosis (18) to the proximal orthosis (16) about a wrist axis (50; 51) substantially perpendicular to the orthosis longitudinal axis (24), wherein the wrist axis (50; 51) is either a wrist flexion / extension axis (50) oriented substantially parallel to the lateral gripping axis (36) to correspond to the user’s wrist flexion / extension axis when the device (10) is mounted to the user’s arm, or a wrist ulnar / radial deviation axis (51) oriented substantially perpendicular to the lateral gripping axis (36) to correspond to the user’s wrist ulnar / radial deviation axis when the device (10) is mounted to the user’s arm; and a controller (30) communicatively coupled with the one or more sensors (42) and the finger actuator (38), the controller (30) configured to operate the finger actuator (38) to actuate the finger joint (34) to rotate the finger orthosis (20) based on the sensor output.

17. The powered orthotic device of claim 16, wherein the one or more sensors (42) form a sensor unit (31) that connects the proximal orthosis (16) to the distal orthosis (18) such that an external torque applied to the distal orthosis (18) is transmitted through the sensor unit (31).

18. The powered orthotic device of claim 16 or 17, wherein the controller (30) is programmed to activate the finger actuator (38) if the sensor output indicates a torque beyond a predetermined threshold value.

19. The powered orthotic device of claim 18, wherein the controller (30) is programmed not to activate the finger actuator (38) if the sensor output indicates a torque that does not surpass the predetermined threshold value.

20. The powered orthotic device of claim 18 or 19 wherein the controller (30) is configured to control the finger actuator (38) to produce a predetermined torque or velocity to rotate the finger orthosis (20) for a predetermined period of time when the sensor output indicates a torque beyond the predetermined threshold value.

21. The powered orthotic device of any of claims 11 to 20, further comprising one or more position sensors (44) communicatively coupled to the controller (30), one or more position sensors (44) configured to measure an angular position of the finger orthosis (20) relative to the distal orthosis(18) and output a position sensor signal, wherein the controller (30) is configured to operate the finger actuator (38) based additionally on the position sensor signal.

22. The powered orthotic device of any of claims 11 to 21 , wherein the controller (30) is programmed to selectively operate in a normal mode, a first grip mode and a second grip mode, wherein: in the normal mode, the finger actuator (38) is controlled to actuate the finger joint (34) to rotate the finger orthosis (20) based on the sensor output; in the first grip mode the finger actuator (38) is controlled independently of the sensor output to actuate the finger joint (34) to rotate the finger orthosis (20) in a first direction; and in the second grip mode the finger actuator (38) is controlled independently of the sensor output to actuate the finger joint (34) to rotate the finger orthosis (20) in a second direction opposite the first direction.

23. The powered orthotic device of claim 22, wherein the controller (30) is configured to switch operation between the normal mode, the first mode and the second mode based on the sensor output.

24. The powered orthotic device of claim 22 or 23, wherein the device (10) comprises a user interface element (46) communicatively coupled to the controller (30), and the controller (30) is configured to switch operation between the normal mode, the first mode and the second mode based on a user input from the user interface element (46).

25. The powered orthotic device of any of claims 11 to 24, further comprising an or the inertial measurement unit (IMU) (62) coupled to the distal orthosis (18) and / or an IMU (62) coupled to the finger orthosis (20), each IMU (62) communicatively coupled to the controller (30), the IMU (62) configured to measure and output one or more IMU signals indicating velocity and / or acceleration of the distal orthosis (18) and / or finger orthosis (20), wherein the controller (30) is configured to operate the finger actuator (38) additionally based on the one or more IMU signals.

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