EP3270862A1

EP3270862A1 - A modular universal joint with harmonised control method for an assistive exoskeleton

Info

Publication number: EP3270862A1
Application number: EP15717587.8A
Authority: EP
Inventors: Gurvinder Singh Virk; Usman HAIDER; Indrawibawa I NYOMAN
Original assignee: Phasex AB
Current assignee: Phasex AB
Priority date: 2015-03-19
Filing date: 2015-03-19
Publication date: 2018-01-24
Also published as: WO2016146960A1

Abstract

There is described a modular universal mechanism, system and method able to provide physical assistance at user upper- and lower-body joint as needed to the wearer by means being able to be configured to meet the individual needs. The design provides assistive non-medical exoskeletons to be realised and operated via a new type of controller; this control strategy is referred to as the "Harmonised controller" which is capable of providing the physical assistance in a comfortable and natural way, where the physical assistance is automatically adjusted to supplement the power provided by the user so that required activity can be performed without causing fatigue in the user. The exoskeleton, provides physical assistance to supplement the muscle effort of elderly persons and can also reduce/increase the muscle effort for a normal fully active person. The mechanism and controller are scalable and reusable.

Description

A Modular Universal Joint with Harmonised Control Method for an Assistive

Exoskeleton

Field of Invention

The present invention relates to a novel universal jointed mechanism suitable for use with an assistive non-medical exoskeleton; and a user-centred control of an assistive non-medical exoskeleton joint, such that it provides the user physical assistance in movement. The invention further relates to an orthotic exoskeleton provided with one or more of said universal jointed mechanisms; and to a method of controlling an orthotic exoskeleton.

Background of the Invention

The present invention relates to a novel universal jointed mechanism and user-centred control of an assistive non-medical exoskeleton joint such that it provides the user, who is primarily a healthy elderly person facing difficulty in performing daily living activities to maintain an active life-style, physical assistance to help make movement. The motions required by an elderly person can be varied and include activities such as standing and maintaining balance unaided, walking, performing sit-to-stand/ stand-to- sit transfers, going up/down stairs, etc. Description of state of the art

Research and development in exoskeletons has recently picked up pace however the focus of the R&D remains focused on the medical sector with exoskeletons that assist a spinal cord injured person or for rehabilitation of stroke victims, etc. Some of these medical exoskeletons are currently in the market as products. However, the field of non-medical assistive exoskeletons still remains largely untapped with only a few examples available. Current research in exoskeletons does not focus on developing mechanisms that are modular, reusable and adjustable. In addition, research in the control methods used either makes use of EMG sensor signals to identify the intention of the person to move and provide physical assistance based on that or else imports conventional robotic methods to control the exoskeletons.

Current assistive exoskeletons for spinal cord injured persons use actuators to provide the full assistive torque at the joints, resulting in bulky designs which are slow in their movement. Meanwhile other assistive exoskeletons for rehabilitation purpose are not designed to be very flexible and are unsuitable for being adapted to individual needs.

Electromyography (EMG) is an electrodiagnostic technique for evaluating and recording the electrical activity produced by skeletal muscles. An electromyograph detects the electrical potential generated by skeletal muscle cells when these cells are neurologically or electrically activated. However, EMG based control signals of exoskeletons have the drawback that the EMG sensors have to be gelled with the skin of the user and the exoskeleton has to be tediously calibrated for each individual user. Furthermore the variability of EMG signals across different people means that the use of the same exoskeleton for different users is difficult. Although EMG based controllers for exoskeletons can provide good estimation of the required assistance, they are not practical for everyday use.

Other methods such as impedance based control methods for exoskeletons make use of other information, such as, force/ pressure or kinematic data, to identify the interaction forces between the exoskeleton and the human; and then to try to provide the required force. Although impedance based controllers can be effective in providing some fixed level of physical assistance to reduce human muscle effort in performing normal living motions, such controllers are unable to provide variable assistance as the need changes due to the state of the human wearer. Furthermore, the use of impedance based controllers is based on the model of the human and exoskeleton requiring various detailed information about the human parameters to be known, such as limb inertias, limb length, weight, etc., making it a complex control method to implement practically and not fully effective when it is required to provide variable physical assistance as needed over a prolonged period. Therefore, specially tailored exoskeleton mechanisms and control methods are needed that can standardize the development of exoskeletons for healthy humans still having motion functionalities.

Furthermore, the manufacturing methods need to be easily implementable for mass production by providing modular and reusable mechanisms such that they can be easily extended from one Degree of Freedom (DOF) to multiple DOFs, for configuration to meet individual needs. Also, the control method needs to be simple to implement, not relying on complex EMG based signals or needing many detailed parameters of each user to be able to provide the variable physical assistance to the user as needed rather than be fixed to a manually set level.

Summary of the Invention

According to a first aspect of the invention there is provided a modular universal joint assembly suitable for use with an assistive non-medical exoskeleton, said modular universal joint assembly comprising a motor as an actuator, said motor being operably linked to a gear assembly and a controller {hardware and control software); and joined to a user coupling attachment, wherein the user coupling attachment is provided with one or more sensors (having redundancy and diversity). The universal joint assembly as hereinbefore described is modular such that it can be used at any articulation point of the user, e.g. elbow joint, knee joint, hip joint, etc., to assist the user in performing a desired movement about the articulation point.

The universal joint assembly is further advantageous in that it is easily attachable/ detachable, reusable and scalable, to allow various bespoke configurations to be realized as needed by an individual user.

The one or more sensors may include one or more types of sensors and may comprise force sensors, accelerometers, gyros, etc. The sensors may be embedded in the user coupling attachment, such that they provide a signal to the controller based on an electrical signal collected from the user's limb, e.g. lower leg, upper arm, etc. The sensors will generally comprise force measuring sensors, such as FSR sensors (Force Sensitive Resistor), but not limited to, which measure the force applied, through a conductive pad. More the force applied, the greater the electrical activity. Such sensors are known to the person skilled in the art and are commercially available. Thus, the sensors provide an estimation of the force generated by a user during movement of limbs. The force is based upon measurements of the FSR sensor.

The motor is operably linked to the gear assembly. The motor or actuator functions as the means for generating rotational motion of the exoskeleton. The motor will be connected to the gear assembly, whilst being controlled by the main controller located on the exoskeleton. The motor type can be formed from any power source, such as, electric, pneumatic, and hydraulic. The motor and the gear assembly are pivotally mounted so that they can together rotate through at least 90 degrees.

The motor may comprise a conventional motor known in the art. Such motors include, but shall not be limited to, a harmonic drive motor, a servomotor, a stepper motor, a brushless electric motor (that can divide a full rotation), a piezo motor or an ultrasonic motor. It will be understood that when more than one motor is present, one or more different motors may be used.

The number and arrangement of the motors may vary depending, inter alia, upon the desired use of the exoskeleton. The gear assembly may comprise a single component which directly fastens to the motor. The use of a T-joint fastener is especially preferred since it can act to decrease the rotational movement from the motor and enhance the torque. The gear can be formed in a variety of standard mechanisms known in the art. The motor is operably linked to the gear such that, when operating, the motor will rotate or spin the gear or wheel. Step-down gearing, may provide high torque and step-up for responsive movement.

The fastener may comprise a bolt or other mechanism such as a twist-lock device. A preferred fastener is a T-slot fastener. Such a T-slot fastener will generally comprise a substantially T-shaped protruding member which is capable of connecting with a corresponding T-shaped groove. In the embodiment shown, the T-shaped protruding member is located on the bracket whilst the T-shaped groove is located on the exoskeleton. The T-slot functions as a mechanical attachment from one joint to the other. It can be placed on the active joint or on the passive joint. Due to the nature of the shape, it can sustain radial and axial motions.

With a T-slot fastener the installation process may be carried out by sliding the T- shaped protruding member into a corresponding T-shaped groove, and locking it. Generally, the gear assembly is the single component which directly connects to the T-slot to transfer the rotational movement from the motor and enhancing the torque.

The controller will generally be a "harmonised controller", which is a new type of control strategy designed to provide the user with supplemental physical assistance as needed to perform the desired motions in a natural and automatic manner. The control method adds the supplemental energy via the worn exoskeleton to the human when it detects that the energy being provided by the wearer is not sufficient to perform the desired activity as required. The overall solution is able to adjust the supplemental energy supplied. As a person ages, the supplemental energy supplied to the exoskeleton will need to increase in order to bridge the growing gap between what the human can provide and what is needed. The "harmonised control" caters for this need based on the signals collected from sensors placed on the limb joints (such as force sensors placed at the lower leg and upper arm). Furthermore the control method can also assist normal fully able users (adults and children) to reduce/increase their muscle effort in performing daily living activities. Reducing effort in this way can make it easier to perform a variety of motions whereas, increasing effort will enable exercising solutions to be developed for various applications for the general public as well as specialised training solutions for elite athletes. The "harmonised controller" uses force sensor signal as an error signal to generate a signal for the motor to provide the torque from the exoskeleton to supplement the human-exoskeleton system. The error signal is the difference between the joint's current position and the human desired angular position. The error can be used in a conventional proportional, integral, derivative controller in any of the combinations to achieve the desired motion. It generates a signal for the motor to provide the torque from the exoskeleton to supplement the human-exoskeleton system.

The coupling attachment comprises means for securing the modular universal joint assembly to a user. Said coupling attachment may comprise one or more bands or straps adapted to secure to or wrap around a user's limb and/ or torso. Other methods of securing items are known to the person skilled in the art and may suitably be used. Typically, straps may be made from a flexible material or fibre as are known in the art. The user coupling attachment may desirably be adjustable and will generally be provided with means for securing the modular universal joint assembly to a user.

According to a further aspect of the invention there is provided an assistive nonmedical exoskeleton comprising one or more a modular universal joint assemblies, each of said one or more modular universal joint assemblies comprising a motor as an actuator, said motor being operably linked to a gear assembly and a controller {hardware and software algorithms); and joined to a user coupling attachment, wherein the user coupling attachment is provided with one or more sensors.

As hereinbefore described, the sensors generally comprise FSR based sensors (amongst others) which provide an estimation of the user intent and the force exerted by a user's limb during movement. The assistive non-medical exoskeleton will include a harmonised control which, in use, is provided with an error signal which comprises the difference between the current position of a user's joint with the desired position. According to a yet further aspect of the invention there is provided a method of controlling an assistive non-medical exoskeleton or an exoskeleton joint actuator by the use of a harmonised control, said harmonised control being provided from a force sensor signal understood as an error signal which comprises the difference between the joint's current position and the desired position. The exoskeleton of the invention is advantageous in that, inter alia, it provides assistance to the user in a natural and ergonomic way via the exoskeleton actuators at appropriate joints. The assistance needed is interpreted from the human provided error signals. The exoskeleton can provide assistance such that the human muscle effort of the user is reduced/ increased as desired in performing various motions. The exoskeleton provides assistance in any daily living task such as standing/balancing, walking, sit-to-stand/ stand-to-sit transfers, manipulation, reaching to grab objects from the floor, carrying shopping, etc.; and can also allow the user to select at what level physical assistance is provided by the exoskeleton.

The method of the invention can be extended to multiple-DOF exoskeletons, generally independent of the configurations and couplings. Furthermore, the controller provides assistance to each of the joints in a natural and ergonomic way. The controller can provide assistance to each of the joints as required by each joint and is independent of the coupling when this is appropriate for simplicity, but forces in multiple joints can be optimised using multivariable methods.

Detailed Description

The detailed description of the mechanism and the control method is presented here with references to figures; the figure reference number corresponds to the figure in which the reference number is first used. Description of Drawings

FIG. 1 : Illustrates the Modular Universal Joint (1) mechanical components attached to the waist structure (2), which consists of a T-slot attachment mechanism (3), a gear assembly (4), motor actuator (5), and adjustable coupling attachment (6) with attached force sensors (7).

FIG. 2: Illustrates the use of the Modular universal joint as a 1DOF assistive exoskeleton (8) worn by a human user for hip assistance. The coupling to the human user embodies the force sensors based on which the harmonised controller provides the automatically variable needed physical assistance.

FIG 3a, 3b, 3c: The figures illustrate the control architecture of the "Harmonised controller" based on force signal feedback from human, understanding of that force signal as the difference between the desired position of the human limb and its current position to generate the required assistance from the exoskeleton (at the joint level) to supplement the instantaneous human effort being provided and hence allow the wearer to perform the desired motion. These figures show the case of a single jointed assistive exoskeleton.

FIG 4: Illustrates the Modular Universal Joint (1) as a multi-DOF assistive exoskeleton (8) worn by a human user. Modular Universal Joint (1) is provided with a hip actuator (5a), knee actuator (5b) and an ankle actuator (5c). The mechanism of the Modular Universal Joint (1) allows for easy extension into more complex configuration exoskeletons for individualized solutions. FIG 5 : This figure illustrates the use of the "Harmonised control" method in a setting of a multiple DOF exoskeleton with physical assistance being provided at multiple joints. The figure shows that the control of each joint can be independent from the others based on signals from the limb of the joint. The method can be coupled for complex motions where optimization of the forces over several joints is needed via a multivariable method as needed.

The mechanical mechanism is presented as one assembly system. The figures are for illustrational purpose only. For the motor and gear components, any type of specifications can be used, while how the connections constrain the joint angular motions should be restricted.

The control method is presented here as an algorithm, however the steps in the algorithm require physical manipulation of physical quantities. These can take the form of electrical, magnetic signals that are manipulated in some way or stored, compared or combined. In the description these signals and physical quantities are referred with symbols or labels to make it convenient to understand. The algorithm can be stored in a computer or another electronic processing device in the form of electronic instructions with readable storage/memory such as RAM, ROM, EPROM, EEPROMS; CD-ROM, Floppy Disk, DVD or any type of media that can be used for storing electronic instructions. Mechanism "Modular Universal Joint"

The mechanism of the Modular Universal Joint is that it should be easily attached/detached, scalable, and reusable for all the joints on the exoskeleton.

FIG 1 illustrates the components of the joint. The T-slot functions as a mechanical attachment from one joint to the other. It can be placed on the active joint or on the passive joint. Due to the nature of the shape, it can sustain radial and axial motions. Meanwhile the installation process is done by sliding it to the housing, and locking it. The locking mechanism here can be performed by a bolt or other mechanical mechanism such as a twisting lock device.

The gear assembly is the single component which directly connects to the protruding T-slot to transfer the rotational movement from the motor and enhancing the torque. The gear can be formed in a variety of standard mechanisms.

The motor actuator functions as the main rotational motion generator. It will be connected to the gear assembly, while controlled by the main controller located on the exoskeleton. The motor type can be formed from any power source, such as, electric, pneumatic, and hydraulic.

The coupling attachment functions as the main connection between the exoskeleton and the human wearer. The component is easily adjustable to a variety of normal human shapes and unique body segment lengths. On the coupling force sensors are attached and these are located on various positions as needed to perform desired motions. These positions can include the front, rear and at any other angular position. FIG 4 illustrates the mechanism extended to a multi-DOF setting. The same Modular Universal Joint mechanism is used at each joint where in the actuator and gears can be changed depending on the specific and individual needs at each joint.

Harmonised Control

The description provided here takes single jointed exoskeleton as an example worn by the user on any upper or lower limb joint; however it is not confined to this description and can be used for any other combination of joints for upper or lower body exoskeletons in a multi DOF setting.

The harmonised control method is for use in assistive exoskeletons which are worn by the healthy users who have full or near-full functionality to perform daily living activities such as standing/balancing, walking, carrying shopping home, manipulation, etc. FIG 3a illustrates in a simple way the overall system in which a human provides torques labelled " τ_Α " to the joints and torques labelled " r_e " are provided by the exoskeleton. The subscript "h" in FIG 3a 3b, 3c refers to the human and subscript "e" refers to the exoskeleton. The sum of these torques, i.e. " τ_Α + r_e " are passed through the joint dynamics and result in the movement of the human+exoskeleton combination moving through an angle " 0". This happens due to the physical coupling of the exoskeleton with the human as explained in the mechanism. FIG 3b presents a more detailed block diagram of the method, where is the desired angular position which the human wants to move his/her joint to (note this is only known to the human, and this desired position generates control signals from the human to the muscles which produce " τ_Α " for the movement of the joint. If the user has full functionality this will result in full achievement of the desired position in the required timescales. However when the human has some loss in physical functionality (due to being tired for example), this will not be achieved as required and he/she will either keep trying to achieve this or will try other limited movement to perform the desired motion. The force sensor embedded in the coupling to the human (on the front and back as illustrated in FIGs 1, 2) picks up the signals of the human intention to still want further motion; based on these signals the exoskeleton controller generates signals for the exoskeleton motors which in result produce torque " r_e " that can supplement the human torque " τ_Α " to achieve the desired angular position " 0" of the joints. The exoskeleton control will try to reduce the force signal to the minimum by providing assistance torques via the exoskeleton motors. FIG 3c illustrates the Harmonised control method in full detail where the signals picked up from the human limb via the embedded force sensors in the exoskeleton coupling to the user define the error difference between the user's current position and their desired position (only known by human) which passes through inherent delays of the sensor labelled as " e ". This can be written as:

β = φ - θ_ά )—

s + a

Where " a " is the estimated delay due to the sensor which is dependent on the internal sensor dynamics. This feedback architecture differs from conventional control feedback architectures in the way that the signals are picked up from the human- exoskeleton where system 1, (the human) is considered as the feedback to system 2 (the exoskeleton) which is coupled with system 1. This is not the case in conventional feedback control systems. Furthermore the human reference input is not known to the control system and only the error is inferred from the human provided force sensor's signal. An understanding of this sensor's signal gives an error signal which is perceived as lack of energy in the human to reach the desired position. If the error signal is high it means that higher assistance is required and it decreases as the sensor signal decreases. The exoskeleton low level position controller can take many formats which exist in the control literature ranging from model-based controllers to conventional proportional, integrator, derivative (PID) controllers which can be in the form of full PID or PD can in full parallel PID form is as:

T = K_p (l + T_ds + -)

Such controllers required the values of " K_p ,T_d, T_i " to be determined using methods like Ziegler-Nichols, etc. The values generated by the exoskeleton controllers are taken as the torques " r " which are converted to current signals "7_e " using motor torque constants so that the signals passed to the motors generate the torques " τ _e " accordingly and added with the human torques to produce the desired motion of the joints with total torques " τ_ί ". This is expressed as:

The PID controller for the exoskeleton can be replaced with any control that reduces human provided error signals from a variety of sensors. Based on such human-based error signals the physical assistance can be provided in a natural and ergonomic way for supplementing muscle effort as needed. It can also be selected at what level the exoskeleton should start providing the physical assistance. As shown in FIG 1, 2 two force sensors can be used from which allow one to be used instantaneously to assist in the forward or reverse direction. Other sensors placed at any angular position of the joint can provide supplementary motion in any direction as needed.

The harmonised control method can be implemented by deploying human based sensors to provide motion errors from what is desired. As an example the use of force sensors placed on the human limb to be assisted is a convenient way of ensuring desired motion trajectories are realized. The force sensor signals can be used as a convenient feedback command signal to drive the exoskeleton and the motor control can be implemented using the PID method to have inner loop for precise current control. The exoskeleton inputs the energy to the human+exoskeleton system in a natural way and the total energy will be the sum of energy from the human and from the exoskeleton. FIG 3c illustrates this overall concept and it can be implemented using appropriate hardware and software. The controller can be analog or digital depending on the type of the motor controller.

FIG 5 illustrates the harmonised control method used in the multi-DOF assistive exoskeleton as illustrated in FIG 4. Harmonised control can work independently from the coupling between the multiple limbs of the human when this is appropriate. FIG 5 illustrates, as an example, the harmonised control for the exoskeleton assisting hip and knee joint of the human user. The subscripts "hh" refer to human hip, "hk" to the human knee, "eh" for the exoskeleton hip and "ek" for the exoskeleton knee. The error signals in the overall control system are provided by the force signals for the hip assistance are collected from the human thigh and for the knee assistance from the human shank as illustrated in FIG 4. As shown in FIG 5 the harmonised control approach for the hip and knee can work independently of each other. In this way the assistance can be provided in a natural way as needed for each of the joints. The user might have requirements for more physical assistance in one joint than another and this is easily catered for within the harmonised control method.

0474P.WO.Spec(4)

Claims

1. A modular universal joint assembly suitable for use with an assistive nonmedical exoskeleton, said modular universal joint assembly comprising a motor as an actuator, said motor being operably linked to a gear assembly and a controller {hardware and control software); and joined to a user coupling attachment, wherein the user coupling attachment is provided with one or more sensors.

2. A modular universal joint assembly according to claim 1 wherein the one or more sensors include one or more types of sensors.

3. A modular universal joint assembly according to claims 1 or 2 wherein the one or more sensors comprise force sensors, accelerometers or gyros.

4. A modular universal joint assembly according to claim 3 wherein the one or more sensors comprise force sensors.

5. A modular universal joint assembly according to any one of the preceding claims wherein the one or more sensors are embedded in the user coupling attachment.

6. A modular universal joint assembly according to any one of the preceding claims wherein the one or more sensors provide a signal to the controller based on an electrical signal collected from the user's limb.

7. A modular universal joint assembly according to any one of the preceding claims wherein the one or more sensors comprise biometric sensors.

8. A modular universal joint assembly according to any one of the preceding claims wherein the one or more sensors comprise FSR sensors.

9. A modular universal joint assembly according to any one of the preceding claims wherein the motor is operably linked to the gear assembly.

10. A modular universal joint assembly according to any one of the preceding claims wherein the motor is connected to the gear assembly, whilst being controlled by the main controller located on the exoskeleton.

11. A modular universal joint assembly according to any one of the preceding claims wherein the motor and the gear assembly are pivotally mounted.

12. A modular universal joint assembly according to any one of the preceding claims wherein the motor is an electric, pneumatic or hydraulic motor.

13. A modular universal joint assembly according to any one of the preceding claims wherein the motor is a harmonic drive motor, a servomotor, a stepper motor, a brushless electric motor, a piezo motor or an ultrasonic motor.

14. A modular universal joint assembly according to any one of the preceding claims wherein the gear assembly comprises a single fastener component which directly fastens to the motor.

15. A modular universal joint assembly according to claim 14 wherein the fastener comprises a twist-lock device.

16. A modular universal joint assembly according to claims 14 or 15 wherein the fastener comprises a T-slot fastener.

17. A modular universal joint assembly according to claim 16 wherein the T-slot fastener comprises a T-shaped protruding member located on the connecting bracket whilst the T-shaped groove is located on the exoskeleton.

18. A modular universal joint assembly according to any one of the preceding claims wherein the controller is a "harmonised controller".

19. A modular universal joint assembly according to claim 18 wherein the "harmonised controller" adds the supplemental energy via the worn exoskeleton to the human when it detects that the energy being provided by the wearer is not sufficient to perform the desired activity as required.

20. A modular universal joint assembly according to claim 19 wherein the "harmonised controller" uses force sensor signal as an error signal to generate a signal for the motor to provide the torque from the exoskeleton to supplement the human- exoskeleton system.

21. A modular universal joint assembly according to any one of the preceding claims wherein the coupling attachment comprises one or more bands or straps adapted to secure to or wrap around a user's limb and/ or torso.

22. An assistive non-medical exoskeleton comprising one or more a modular universal joint assemblies, each of said one or more modular universal joint assemblies comprising a motor as an actuator, said motor being operably linked to a gear assembly and a controller {hardware and control software); and joined to a user coupling attachment, wherein the user coupling attachment is provided with one or more sensors.

23. An assistive non-medical exoskeleton according to claim 22 wherein the one or more sensors include one or more types of sensors.

24. An assistive non-medical exoskeleton according to claims 22 or 23 wherein the one or more sensors comprise force sensors, accelerometers, gyros, etc.

25. An assistive non- medical exoskeleton according to claim 22 wherein the one or more sensors comprise force sensors.

26. An assistive non-medical exoskeleton according to any one of claims 22 to 25 wherein the one or more sensors are embedded in the user coupling attachment.

27. An assistive non-medical exoskeleton according to any one of claims 22 to 26 wherein the one or more sensors provide a signal to the controller based on an electrical signal collected from the user's limb.

28. An assistive non-medical exoskeleton according to any one of claims 22 to 27 wherein the one or more sensors comprise biometric sensors.

29. An assistive non-medical exoskeleton according to any one of claims 22 to 28 wherein the one or more sensors comprise FSR sensors.

30. An assistive non-medical exoskeleton according to any one of claims 21 to 22 wherein the motor is operably linked to the gear assembly.

31. An assistive non-medical exoskeleton according to any one of claims 22 to 30 wherein the motor is connected to the gear assembly, whilst being controlled by the main controller located on the exoskeleton.

32. An assistive non-medical exoskeleton according to any one of claims 22 to 31 wherein the motor and the gear assembly are pivotally mounted.

33. An assistive non-medical exoskeleton according to any one of claims 22 to 32 wherein the motor is an electric, pneumatic or hydraulic motor.

34. An assistive non-medical exoskeleton according to any one of claims 22 to 33 wherein the motor is a harmonic drive motor, a servomotor, a stepper motor, a brushless electric motor, a piezo motor or an ultrasonic motor.

35. An assistive non-medical exoskeleton according to any one of claims 22 to 34 wherein the gear assembly comprises a single fastener component which directly fastens to the motor.

36. An assistive non-medical exoskeleton according to claim 35 wherein the fastener comprises a twist-lock device.

37. An assistive non-medical exoskeleton according to any one of claims 35 or 36 wherein the fastener comprises a T-slot fastener.

38. An assistive non- medical exoskeleton according to claim 37 wherein the T- slot fastener comprises a T-shaped protruding member located on the connecting bracket whilst the T-shaped groove is located on the exoskeleton.

39. An assistive non-medical exoskeleton according to any one of claims 22 to 38 wherein the controller is a "harmonised controller".

40. An assistive non-medical exoskeleton according to claim 39 wherein the "harmonised controller" adds the supplemental energy via the worn exoskeleton to the human when it detects that the energy being provided by the wearer is not sufficient to perform the desired activity as required.

41. An assistive non- medical exoskeleton according to claim 40 wherein the "harmonised controller" uses an error signal to generate a signal for the motor to provide the torque from the exoskeleton to supplement the human-exoskeleton system.

42. An assistive non-medical exoskeleton according to any one of claims 22 to 41 wherein the coupling attachment comprises one or more bands or straps adapted to secure to or wrap around a user's limb and/ or torso.

43. A method of controlling an assistive non-medical exoskeleton or an exoskeleton joint actuator by the use of a harmonised control, said harmonised control being provided from a force sensor signal understood as an error signal which comprises the difference between the joint's current position and the desired position.

44. A method according to claim 43 wherein the harmonised control method defines the error difference between the user's current position and their desired position which passes through inherent delays of the sensor labelled as " e " and determines:

β = φ - θ_ά )—

s + a where " a " is the estimated delay due to the sensor which is dependent on the internal sensor dynamics.

45. A method according to claim 43 or 44 wherein the controller is a PID controller which calculates the required torque as:

_T = K_p {\ + T_ds + -)

T_{i S} where values of " K , T_d , T_i " are determined using methods like Ziegler-Nichols, etc.

46. A method according to any one of claims 43 to 45 wherein the values generated by the exoskeleton controllers are taken as the torques "r " which are converted to current signals " 7_e " using motor torque constants so that the signals passed to the motors generate the torques " τ _e "and added with the human torques to produce the desired motion of the joints with total torques "τ_ί " expressed as:

47. A modular universal joint assembly, an assistive non-medical exoskeleton or a method as hereinbefore described with reference to the accompanying examples and figures.

0474P.WO.Spec(4)