WO2021032971A1

WO2021032971A1 - Capstan joint

Info

Publication number: WO2021032971A1
Application number: PCT/GB2020/051974
Authority: WO
Inventors: Robert Bloomfield
Original assignee: Mechatech Limited
Priority date: 2019-08-19
Filing date: 2020-08-18
Publication date: 2021-02-25
Also published as: WO2021032970A1; GB201911885D0; GB2586473A

Abstract

According to an aspect of the present invention, there is provided a polycentric joint for an exoskeleton device or system. The joint comprises a first rotatable drum having a first engagement portion, a second rotatable drum having a second engagement portion, and a flexible filamentary member engaged with the first engagement portion and extending therefrom to engage with the second engagement portion. The first and second rotatable drums are configured to rotate about two adjacent respective first and second axes, such that a proportion of the filamentary member engaged with the first or second engagement portions is minimised.

Description

Capstan Joint

Technical Field

The present invention relates to polycentric joints. More specifically, the present invention relates to, but is not limited to biomechanical joints in exoskeletons.

Background of the invention

The term exoskeleton is generally defined in relation to the animal kingdom and may refer to crustaceans or insects amongst other things. An exoskeleton is simply an external skeleton. The exoskeleton in the animal kingdom gives support for muscle attachment and protection from the elements, for example water. Exoskeletons in the animal world limit the size of the animal, because of the necessity for the animal to grow within and be supported by a rigid structure. Insects and crustaceans are both limited in size as a result of this strength to weight ratio. However, crustaceans can be much larger than insects because of the support provided by water.

In the present disclosure, the term “exoskeleton” refers to an external skeletal frame worn by a human. A lower body exoskeleton is a skeletal frame worn over just the legs, an upper body exoskeleton is typically worn over the torso and arms. A full body exoskeleton is a frame worn over both the arms and the legs, connected by a torso of the exoskeleton. Exoskeletons are necessarily anthropomorphic, non- anthropomorphic or pseudo-anthropomorphic as a result of supporting or shadowing the motion of a human operator.

The recording of accurate biomechanical motion of subjects is of increasing importance in many fields of technological development. It may be used for a wide range of applications from gait analysis to diagnosis of physical injuries and degenerative diseases, to generating accurate digital representation of human motion. Digital representations of human motion may further be used in medicine to develop orthotics that mimic the natural motion of patients, or may be used in the entertainment industry to produce immersive customer experiences.

In the field of virtual, augmented and mixed reality there are well developed products that allow a user to control and explore their virtual environment with their upper body, i.e. headsets to track the movement of the head and neck and controllers that register the movement of the hands and arms. However, very few devices enable tracking of the motion of the lower half of the body, or using such tracking to infer physical translation of the player as they walk.

Current solutions tend to fall into one of two camps. The first technique is to map the environment of the user, requiring a labour intensive installation of sensors within the environment, therefore limiting the size of an environment that may be explored. The second method is to either enable or mimic relative movement between a surface and the user. One way of doing this is by installing an omnidirectional treadmill which enables the user to remain located in substantially the same location whilst the surface rotates in response to a user’s movements. Another technique may be to support the user in a harness suspended above a concave low friction surface, allowing the user to exert force on and slip over the surface in an imitation of locomotion.

However, both of these solutions suffer from significant limitations. Omnidirectional treadmills are very large and expensive and require that the user wear a harness. Low friction surface techniques also require that the user wear a harness and require the user to adapt their gait and movements to the concave shape of the surface. Both of these solutions infer a position of the leg based upon the leg being in contact with a sensitive surface. In absence of such contact, the system is unaware of the motion of the leg, excluding a wide selection of movements from detection.

Currently, there are a very limited number of solutions that allow the user to naturally explore and interact with a virtual environment. Further, many current solutions suffer from a spatial limitation in the user environment that these solutions are capable of accommodating. A device that can accurately detect and record the movement of the lower half of a user’s body would enable the possibility of new interactions and generating new movements for a user in a VR (virtual reality) game. Such a device may enable unconventionally swift and accurate motion capture for the creation of computer generated characters in visual media. Further, such a device may be used in physiotherapy to collect data on the movements of specific joints, along with other possible benefits.

Aspects and embodiments in accordance with the present invention were devised with the foregoing in mind. Summary

According to an aspect of the present invention, there is provided a polycentric joint for an exoskeleton device or system. The joint comprises a first rotatable drum having a first engagement portion, a second rotatable drum having a second engagement portion, and a flexible filamentary member engaged with the first engagement portion and extending therefrom to engage with the second engagement portion. The first and second rotatable drums are configured to rotate about two adjacent respective first and second axes, such that a proportion of the filamentary member engaged with the first or second engagement portions is minimised. The provision of a flexible filamentary member as the element transmitting torque between the two rotatable drums removes ‘slack’ or ‘backlash’ caused by the use of cogged joints. That the axes are arranged such that the filamentary member has minimal contact with the engagement portions maximises the efficacy of force transfer by ensuring that the filamentary member extends substantially perpendicular to the axes of rotation. This constraint applies to the axes arrangement, and not the arrangement of the filamentary member perse.

The flexible filamentary member may be configured to trace at least a partial lemniscatic path running about the first rotatable drum and the second rotatable drum. In order to provide contra-rotatory motion of the rotatable drums, the filamentary member must run in a lemniscatic path without the use of further rotatable drums.

The polycentric joint may be arranged such that an incident torque upon the first engagement portion develops an equivalent torque upon the second engagement portion via the lemniscatic arrangement of the flexible filamentary member. In this manner a polycentric joint representative of the mechanical movement of a typical human joint is provided.

The first and second rotatable drums may be arranged within a respective first and second support portion, configured to allow rotation of the rotatable drums and passage of the flexible filamentary member. The support portions allow connection of the rotatable drums to further elements that are not configured to rotate with the drums.

The polycentric joint may be provided with a rotation sensing assembly arranged to sense relative motion between the first or second rotatable drum and the first or second support portion. The provision of such an assembly attached to the support portion and therefore not configured to rotate with the rotatable drums allows precise measurement of both the movement of the rotatable drums and of the polycentric joint as a whole.

The first support portion may be opposed to the second support portion and translationally offset in the first plane from the second support portion.

The first support portion may be aligned with the second support portion and translationally offset in the first plane from the second support portion. These options allow a wide range of configurations, enabled by the manner in which the joint functions. In this manner, the rotation sensing assembly and other parts may be mounted flexibly.

The support member may comprise at least one friction reduction member disposed between an outer surface of at least one first upstanding member and an inner surface of the first rotatable drum and at least one friction reduction member disposed between an outer surface of at least one second upstanding member and an inner surface of the second rotatable drum. The rotatable drums are thus provided with means to rotate freely and with minimum impediment about the upstanding members, within the limits of their construction and attachment to other elements.

The at least one friction reduction member may comprise one or more of: a bushing; one or more bearings; and/or a lubricant.

The first and/or second upstanding member may each comprise at least one magnet, and the at least one magnet may be coaxially aligned with a respective one of the first and/or second axis. Said magnet may form part of the rotation sensing assembly.

At least one of the first and/or second rotatable drum may comprise at least one magnet located on an upper surface and coaxially aligned with the respective first and/or second axis, and wherein the magnet forms part of the rotation sensing assembly. The provision of a magnet as an indicator of relative angle between the rotating drum and the support portion, rather than the use of (for example) a potentiometer, further reduces resistance to rotation of the rotatable drum relative to the support portion.

The poles of the at least one magnet may be perpendicular to the first and/or second axis. Thus increasing the relative change of flux orientation for a given rotation of a rotatable drum. The flexible filamentary member may be configured in a figure of eight arrangement around the first and second rotatable drum and the flexible filamentary member comprises at least two cross-overs at a point disposed between the first and second rotatable drums. Further to the at least partial lemniscatic path, the filamentary member may be configured to trace a full lemniscatic path about the two rotatable drums, thus increasing the contact surface area and thus the maximum transmissible force between the two drums.

A rate and/or a range of the rotation of the first rotatable drum may be substantially equal to a rate and/or a range the rotation of the second rotatable drum. This enables the joint to replicate the motion of a human joint accurately.

The first rotatable drum and the second rotatable drum may have a range of rotation of at least about 120° in a clockwise and/or anticlockwise direction. This rotation allows better representation of the motion of a human joint.

A first and/or second end of the flexible filamentary member may terminate proximal to the first rotatable drum.

A first and/or second end of the flexible filamentary member may terminate proximal to the second rotatable drum.

A first end of the flexible filamentary member may terminate proximate to the first or second rotatable drum and a second end of the flexible filamentary member terminates proximate to the other rotatable drum.

The first and/or second end of the flexible filamentary member may be configured to terminate internal to the engagement portion of the first and/or second rotatable drum. These features allow flexible termination of the filamentary members which may be necessary to increase or decrease the range of motion of the polycentric joint, or simplify manufacturing processes.

The flexible filamentary member may be configured to apply a sufficient force via the first and second engagement portions to inhibit individual rotation of the first rotatable drum, the second rotatable drum and/or the flexible filamentary member. This may be achieved by increasing the tension of the filamentary member, thus ensuring minimal ‘slipping’ of the joint.

The polycentric joint may be provided with two flexible filamentary members, thus improving reliability should one flexible filamentary member fail. This also reduces the tension required in each filamentary member, reducing wear and fatigue of elements of the polycentric joint. The first and second engagement portions may trace respective rotation profiles in a ratio of substantially 1:1 to each other. Non-cylindrical engagement portions may be provided in the joint, as long as the engagement portions trace a 1 : 1 ratio of each other such that overall rotation of one rotatable drum is equal and opposite to the overall rotation of the other rotatable drum.

The rotation sensing assembly may further comprise a sensor configured to sense a rotation of the at least one magnet relative to the sensor.

The sensor may be a magnetic resistive sensor. The use of a device that is operable to detect relative magnetic flux orientation to detect relative orientation of a magnet mounted to the support portion and the rotatable drum further facilitates a low-resistance joint with accurate angle measurement.

The at least one sensor may be located on an upper surface of the first and/or second rotatable drum, or the at least one sensor may be located internal to at least one of the first and/or second upstanding member. The placement of the sensor is complementary with the placement of the magnet, such one of the sensor or magnet is placed upon either the rotatable drum or the upstanding member. This allows multiple configurations of the sensor and the magnet that achieve similar accuracy.

The polycentric joint may further comprise at least one processor operably linked to the rotation sensing assembly to receive data thereform. This processor allows the data provided by the sensor of the rotation sensing assembly to be analysed.

The polycentric joint may further comprise at least one further sensing assembly configured to sense one or more of: acceleration; location; orientation; force; speed; velocity; angular velocity; angular displacement; angular acceleration; torque; impulse; rotation; momentum; and/or temperature.

The at least one further sensing assembly may be operably linked to at least one processor. These further sensors may provide further data to the processor to contextualise the data from the magnetoresistive sensor.

The at least one processor and/or at least one further processor may comprise at least one connection member configured for physical and/or wireless connection with a computing device, allowing the data, analysis thereof, or resulting analyses, to be shared between the processors and the computing device. The polycentric joint may further comprise at least one actuator configured to actuate rotation of at least one of the first and/or second rotatable drum. Thus allowing actuation of the joint in an embodiment where actuation by a non-human influence is preferred.

Each of the first and/or second rotatable drum may comprise at least one attachment portion configured for attachment of one or more frames. The polycentric joint may therefore be configured for attachment to a preferred object.

Brief Description of the Drawings

One or more embodiments in accordance with the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 depicts a front view of two modules 11, 12, each comprising a first frame unit 13, a joint 14 and a second frame unit 15, in a system 10, each connected by a data communication cable 16;

Figure 2 depicts a second view of two modules 11, 12 equipped with strapping systems 22 and 23 and further comprising data communication cable 16;

Figure 3 depicts a single module 11 comprising frame members 13, 15, exoskeleton joint 14, and data communication cable 16;

Figure 4 depicts a single module from a front view, showing the frame units 13, 15, the exoskeleton joint 14, and data communication cable 16;

Figure 5 depicts a side view of a single module;

Figure 6 depicts a geared polycentric joint for use in an exoskeleton joint, showing rotatable drums 62 contained within housing 61 , the rotating drums each having teeth 64, the rotatable drums arranged about shafts 65 and held by retention member 72, also illustrated is the pitch diameter P;

Figure 7 shows a cross-sectional depiction of the joint of Figure 6, showing reference element 71 fixed to housing 61 via shaft 65;

Figure 8 depicts a cross-section through a capstan polycentric joint, showing cables 81 and 82, friction reducing member 83, rotatable drums 62, housing 61 , reference element 71 , structural member 85 and rotation detecting sensor 84;

Figure 9 depicts an exploded view of a first frame unit 13 of a module, showing polycentric joint 14, housing 61, rotatable drum 62, structural member 85, circuit board 91 , second structural member 92, housing portion 93, fixings 96, fixings 97, and cap 98;

Figure 10 depicts an exploded view of a first frame unit of a module, further illustrating the engagement formation 101 and at least one processor 102;

Figure 11 depicts an exploded diagram of a second frame unit 15, further structural member 111, rigid layer 112, conformable layer 113, and engagement formation 114; and

Figure 12 depicts an alternate cross-sectional view of a capstan polycentric joint through the plane of rotation, showing a single cable 81 for illustrative purposes, rotatable drums 62, housing 61 and wire terminations 121.

Detailed description

A motion capture module 11 for a joint may be implemented in a number of ways, some of which are described in the following description. Particularly, implementations concerning the use of polycentric joints as a sensed rotational axis and using remote sensors to a sensed rotational axis are disclosed.

Embodiments described herein make reference to both cogged polycentric joints and capstan polycentric joints. For the purposes of the disclosure, any embodiment disclosed as using a cogged polycentric joint may be worked by replacing the cogged joint with a polycentric capstan joint as described herein.

As referred to herein, terminology common to the art of anatomical description is used to describe features and arrangements of the disclosed implementations and have their usual meaning in anatomy according to context or unless context indicates otherwise. Non-limiting definitions of anatomical terms used in this specification are listed below:

• Anterior - the direction characterised by moving from the rear to the front of a body in a standing position.

• Posterior - the direction characterised by moving from the front to the rear of a body in a standing position.

• Superior - towards the top of a body when the body is in a standing position. • Inferior - towards the bottom of the body when the body is in a standing position.

• Left - when referring to features dependent on a user’s body, this will mean the left side of the user from the user’s perspective.

• Right - when referring to features dependent on a user’s body, this will mean the right side of the user from the user’s perspective.

• Medial - towards the centre of a body normal to the superior-inferior axis.

• Lateral - away from the centre of a body normal to the superior-inferior axis.

• Medial rotation - a rotation such that the lateral surface of an object moves in an anterior-medial direction, whilst the medial surface moves in a posterior-lateral direction.

• Lateral rotation - a rotation such that the lateral surface of an object moves in a posterior-medial direction, whilst the medial surface moves in an anterior-lateral direction.

• Median plane - a two-dimensional anatomical plane bisecting a body, the plane extending in the posterior-anterior axis and the superior- inferior axis, wherein the plane is defined by passing through centre of a body.

• Sagittal plane - a two-dimensional anatomical plane extending in the posterior-anterior axis and the superior-inferior axis, wherein the plane is defined by passing through the shoulder and hip of a body.

• Coronal plane - a two-dimensional anatomical plane bisecting a body extending in the superior-inferior axis and the medial-lateral axis, wherein the plane is defined by passing through the centre of the body.

• Horizontal plane - a two-dimensional plane extending in the posterior- anterior axis and the medial-lateral axis.

• Proximal - referring to a limb, in a direction towards a joint closest to the core of a body.

• Distal - referring to a limb, in a direction away from a joint closest to the core of a body. Further, the term ‘torsional stiffness’ as used in the present disclosure has the meaning as understood in the art of meshed gear systems. That is to say, the responsiveness of an output of a geared mechanism to a torsional force applied at the input, which may characterise efficiency and rapidity of transfer of the torsional force through the device. It will be understood that the term ‘torsional stiffness’ may be applicable to non-geared torsional transmission devices, such as capstan devices.

In the present disclosure the term ‘module’ in the context of gears is used in the sense as accepted in the art of gear design. For the avoidance of doubt, it will be understood by the skilled person that the module of a gear is abbreviated to ‘mod’ in the art, and would recognise it as a separate term to that of the module that the present disclosure describes.

A module 11 for sensing movement of an anatomical joint may be implemented in a variety of ways. This is because the ability to sense a biomechanical joint motion may be achieved by multiple embodiments using examples of the inventive concepts detailed herein.

Figure 1 illustrates an embodiment of module 11 wherein a first frame unit 13 is configured to be located superior to a user’s knee by being conformable to the lower thigh of a human leg. In the illustrated embodiment, the first frame unit 13 is affixed to one end of an exoskeleton joint 14 where the first frame unit is located laterally to the exoskeleton joint. It will be recognised that other arrangements of the first frame unit 13 and exoskeleton joint 14 may be suitable, such as arranging the exoskeleton joint 14 laterally to the first frame unit 13, or arranging the first frame unit 13 substantially in-line with the exoskeleton joint 14.

In the illustrated embodiment, a second frame unit 15 is affixed to another end of the exoskeleton joint 14 and arranged to be located inferior to a user’s knee. The second frame unit 15 is configured to be attached to the shin of a user by being conformable to the upper shin of a human leg. In the illustrated embodiment the second frame unit 15 is arranged medially to the exoskeleton joint 14. It will be recognised that other arrangements of the second frame unit 15 and exoskeleton joint 14 may be suitable, such as arranging the exoskeleton joint 14 medially to the second frame unit 15, or arranging the second frame unit 15 substantially in-line with the exoskeleton joint 14. In the illustrated embodiment, a second module 12 is configured to be used in conjunction with the first module 11 in system 10 via data communication cable 16, which may be in communication with the processors of modules 11 and 12. In another embodiment, data communication between the modules 11 and 12 may be achieved via wireless transmission protocols. In the illustrated embodiment, data communication cable 16 is arranged to extend upwards and away from the modules anteriorly, so as to avoid encumbering the user. In other embodiments, the cable may be configured to extend posteriorly and/or to be affixed to the user.

In the embodiment illustrated in Figure 3, a module 11 is used for detecting motion of a knee for use in computer input, control or virtual reality applications. Multiple modules may not be required if, for example, a single knee of one side of the user would be able to sense that knee’s motion. However, for computer input, control or virtual reality applications disclosed herein where locomotion detection is required and, importantly, immersing the user’s legs into virtual reality, sensing of both legs may be required or at least desirable. This is due to the ability to perform certain motions of, for example, one leg without inducing motion in the other leg.

A rotation sensing assembly may be arranged on the inside or outside of the knee as the axis of rotation for the knee carries on through the joint.

A knee axis is not always located in the same place due to biodiversity of human anatomy and/or trauma. The module is configured such that it can accommodate a user with Varus or Valgus legs, in which case the rotational axis of the knee will be irregular. The typical variation for an axis tilt that could be accommodated is +/- 5 degrees. However, greater axis tilts could be accommodated by the module. This is achieved by means of a compliant frame of the module, increasing comfort and accessibility to a larger range of users.

However, a module 11 could also include a pivot for this compliant feature. Both modalities would achieve the same outcome. Extant in the art are medical knee braces that use fixed geometry instead of a compliant or pivot feature. This is typically overcome in that medical braces will be customised by bending the structure to the individual user. The module 11 disclosed herein addresses and may overcome this issue by having a conformable frame.

The described embodiment consists of a double-sided knee exoskeleton, which attaches to the thighs and lower leg with a sensed joint 14 in the middle. A joint for the exoskeleton may be fitted medially, laterally, or on both sides of each knee depending on the application. A polycentric joint may approximate the biomechanical behaviour of the human user’s anatomical knee.

Figure 2 illustrates an embodiment of the system 10 of two modules 11 and 12, which are linked by data communication cable 16 and further linked to an external processor or computer via data communication cable 21. In another embodiment, data communication with an external processor and/or computer may be achieved via wireless protocols. The system 10 of Figure 22 illustrated that the first frame units are equipped with strapping system 22 and the second frame units are equipped with strapping system 23.

In the illustrated embodiment, strapping systems 22 and 23 comprise elastic material affixed to a frame unit. The elastic material is shaped as a strap and arranged to have an adjustable length. In the illustrated embodiment, two elastic straps are interlinked by adjustment members such that the movement of either adjustment member may effectively shorten or lengthen the overall strap length. In the illustrated embodiment, the elastic material is Prym 38 mm elastic, although it will be recognised that a variety of elastic materials or non-elastic materials may be used in other embodiments, as well as straps of different dimensions.

In the illustrated embodiment of Figure 3, the strapping systems 22 and 23 are not shown in order to clarify the means by which the systems are affixed to the frame units by feeding the material through a gap 31 in the frame unit and then folding the material such that it may no longer pass though the gap. The material is then fixed in the folded arrangement, in the illustrated embodiment the material is fixed by sewing the fold into the material with a polyester thread, although it will be recognised that other materials may be suitable for sewing the material. It is also disclosed that other methods for fixing a fold in the strap material would be recognised, such as, but not limited to, stapling or gluing.

In the illustrated embodiment, the straps are configured to be affixed to the posterior portion of the frame units and be reversibly attachable to the anterior portion of the frame unit. A retention member 24 (as seen in Figure 2) is configured to reversibly engage with notch 32 such that the elasticated material ‘pulls’ the retention member into a secure position within the notch 32. It will be understood by the skilled person that other reversible attachment means may be used to similar effect with the module, such as but not limited to: magnets; Velcro attachments; snap attachments; etc. Illustrated in Figure 3 is a single module shown in a position that may be caused by the flexion of the leg of a user, illustrating the articulation afforded by a polycentric joint. In the illustrated embodiment, a geared polycentric joint forms the exoskeleton joint such that the module conforms to the limb throughout the natural range of motion of the limb.

As illustrated in Figure 5, a polycentric joint is a double parallel axis joint. A polycentric knee joint may be produced using different mechanical designs to achieve the same or at least similar motion.

In the illustrated embodiments, the torsional stiffness of the exoskeleton joint is configured to maximise the torsional force transmitted from the motion of the limb to the rotational sensor. This may be achieved by selecting a low mod for the gears, or selecting materials with a high stiffness such as carbon steel to form the gears. It would be recognised that other configurations of polycentric joint may be configured to have a high torsional stiffness. A higher stiffness joint is also achieved by using a capstan polycentric joint in place of a cogged polycentric joint. By increasing the torsional stiffness of the joint, the response of the rotational sensor to movement of the limb may be more accurate and prompt than with a lower torsional stiffness.

The polycentric joint of Figure 5 is implemented using two rotatable drums 62, 63, contained within a housing 61, wherein the rotatable drums are configured to rotate about adjacent shafts 65, 66. The rotatable drums of the illustrated embodiment are formed with teeth 64 such that the drums may be considered as cogs. The teeth and drum size are configured such that when the drums are engaged with one another the ratio of rotation of one drum to the other is 1:1. In some embodiments, a wire rope is used instead of configuring the rotatable drums to be formed with teeth. In such an embodiment, the ratio of rotation of each drum to another may be adjusted by adapting the diameter or rotation profiles of the engagement portions of one or both drums.

In some embodiments, the rotation of the drums is configured to be substantially 1:1, or equal. This will ensure that both the rate and range of rotation of each drum matches the other. Substantially equal will be understood to be within tolerance of the identified purpose for the polycentric joint. This ratio may be the ratio may be any of 1 : 1 1 or less, 1 : 1.2 or less, 1 : 1.3 or less, 1 : 1.4 or less, or 1 : 1.5 or less,

In some embodiments the range of rotation of the rotatable drums is configured to be about 120 degrees. The range of motion is determined by the tolerance of the identified purpose of the embodiment, and thus ‘about’ will be understood to mean such a tolerance. In some embodiments the identified purpose is that of replicating the motion of a human joint, for which 120 degrees is preferred, and in such an embodiment the tolerance may be +/- 20 degrees or less, +/- 15 degrees or less, +/- 10 degrees or less, +/- 5 degrees or less, or +/- 1 degree or less.

In some embodiments the ratio may be adjusted to accommodate different users and anatomical differences, or to provide passive feedback and/or assistance with motion of the limb. It will be appreciated that ratios other than 1 : 1 may be used if the ratio difference is not significant over the natural range of motion of the joint in the illustrated embodiment. In some embodiments, the ratio may be 1:2, 1:3, 1:4,

1:5, 1:6, 1:7, 1:8, 1.9 or 1 : 10. Further, the ratio may be any of 1 : 1.1 , 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1 : 1.8 or 1 : 1.9. Which of the rotatable drums (i.e. the drum attached to or engaged with the first frame unit or second frame unit) is configured to satisfy the larger or smaller proportion of a given ratio may be determined by the anatomy of a user, and/or the purpose for which the module is used. That is to say, the ratio of the rotatable drum attached to or engaged with the first frame unit to the rotatable drum attached to or engaged with the second frame unit may be 1 :2 in a first embodiment, whilst in another embodiment it may be reversed such that the proportions are 2:1 instead. In a non-limiting example, the module may be configured to provide assistive or resistive feedback to a user performing a specific motion, in which case a specific ratio may be selected.

In the illustrated embodiment of Figures 6 and 7, the mod and pitch diameter P of the teeth 64 and rotatable drums 62, 63 are selected to minimise backlash in operation of the gears. In the illustrated embodiment, the mod of the gears is 1 and the pitch diameter P is 20mm. In some embodiments, to reduce backlash the mod of the gear may be selected to be less than 1. In some embodiments, to make the module conform to the user the mod may be selected to be greater than 1. In the described embodiment, the rotatable drums are formed from Carbon Steel. It will be recognised that other materials would be suitable for forming the drums, such as (but not limited to): Steel, Aluminium, Bronze, Brass, Iron, sintered metals, or plastics. Optionally or additionally, the drums may be integrally formed with the frame unit to create a lighter module arrangement.

In the illustrated embodiment of Figures 6 and 7, the rotatable drums are configured to rotate about shafts 65 and 66 which are rigidly attached to the housing 61. In the illustrated embodiment, the shafts are a separate object that is push-fitted into the housing, whereby rotation of the shaft is prevented by friction between the housing and the shaft. In some embodiments, the shaft is integrally formed with the housing 61. In some embodiments, the shafts 65, 66 may be secured using other or additional methods, depending on the application for the module. Other methods may involve: welding, brazing, soldering, grub screws, threading, or other methods which the skilled person may recognise as being suitable for an application. Shafts 65, 66 comprise an axial cylindrical space through their centres, into which a bipolar magnet is secured. In the illustrated embodiment of Figures 6 and 7, the housing 61 is formed from Aluminium 6082. Such a material has been selected for its durability and lightweight nature, but it will be recognised that other materials may be suitable such as (but not limited to): steel; stainless steel; resin; plastic etc. One effect of the use of Aluminium as a housing material is that it is a non-magnetic material and therefore has no impact of the operation of the magnetoresistive sensor used to detect relative rotation between the magnet in the shaft and the frame unit.

In the described embodiment, the shafts 65, 66, are formed from Bronze Oilite, which has a low frictional coefficient. It will be recognised that other materials with low frictional coefficients may be used for forming the shafts. It is an effect of the use of Bronze Oilite that it is not magnetic, and so does not interfere in the operation of the magnetic sensor. Another effect is the high resistance to deformation of the material. The skilled person will recognise that other materials may be suitable for the purpose of providing a low friction, resilient and non-magnetic shaft.

In some embodiments a friction reducing member 83 is placed between the shafts 65, 66 and the rotatable drums 62, 63, as illustrated in figure 8. There are therefore multiple methods for achieving low resistance to rotation for the rotatable drums.

In the illustrated embodiment of Figure 7 a thrust washer 72 is arranged on the end of each shaft 65, 66 at the end of the shaft furthest from the housing 61. A push-on fastener 67 is then placed on the end of the shaft such that the fastener 67 secures the washer 72 and rotatable drums to the exoskeleton joint.

As illustrated in Figures 6, 7 and 8, the polycentric joint housing allows access to the rotatable drums on opposite sides. This allows the attachment of the frame units on opposite sides of the exoskeleton joint as described in the foregoing. Such an arrangement allows proper alignment of the rotation sensing assembly. Optionally, the polycentric joint housing may be adapted to allow connection of the frame units to the rotatable drums on a singular side of the housing.

A second embodiment of an exoskeleton joint may be used in combination with the first and second frame units in a module, wherein the exoskeleton joint is a polycentric capstan joint as illustrated in Figure 8.

In the described embodiment illustrated in Figure 8, a polycentric capstan joint has two rotatable drums 62, 63 in a housing configured. Each drum is connected to the other by a wire rope 81 following a generally lemniscatic path about the two drums, such that a torque exerted upon one drum is transmitted to the other drum to achieve a contra-rotation in the second drum. Figure 12 illustrates such a lemniscatic path that will lead about a first drum in one direction (for example clockwise) and then around the second drum in the opposite direction (in this example, counter clockwise) before returning to the first drum to be wound again in the clockwise direction.

The axes of the drums must be arranged such that the proportion of the wire rope in contact with an engagement portion is minimised. Such an arrangement, for example, ensures that the wire rope runs perpendicular to the axis of rotation of the joint. In an embodiment where the rotatable drums are cylindrical in shape, the wire rope then traces a straight line that is parallel with the circular cross-section of the drum and therefore perpendicular to the surface of the engagement portion. By tracing a line perpendicular to the surface of the engagement portion, the portion of the wire rope in contact with the engagement portion is minimised when compared with a non-perpendicular trace which would cover more surface area of the engagement portion.

The wire rope 81 may be wrapped multiple times around each rotatable drum 62, 63 to increase friction between the rope and the drum. Such an arrangement would ensure a greater contact area between the wire rope and the drums, improving torque transfer and thereby torsional stiffness. In the described embodiment of Figure 12, the terminations 121 of the wire rope 81 occur in only one of the rotatable drums. In the illustrated embodiment of Figure 8 two wire ropes are used for redundancy, where the second wire rope terminations occur in the opposite drum to that of the first wire terminations.

Wire terminations 121 are achieved by clamping the ends of a wire within the rotatable drum. This may be achieved, for example, by attaching an object to the end of the wire and inserting the object into a drum in such a way that when the wire is placed under tension, the object holds the wire under strain. It may also be achieved by using, for example, a grub screw to clamp the end of a wire within a rotatable drum.

The effect of using a wire rope capstan to transmit torque from one rotatable drum to the other is to reduce the slack or backlash that is present in a cogged joint (for example caused by space between the teeth of a cog), and increase the torsional stiffness of the joint. Solutions to such a problem are usually approached via complicated helical cog designs, but this would require longer cogs to implement thus making such a joint cumbersome, typically impractically so in an exoskeleton. In the described embodiment, a centre component holds the joint together. When one of the rotatable drums is rotated about its axis the other moves at the same rate and to the same range but in the opposite direction. When implemented in a module, a stem is attached to each shaft such that the stems would form part of the frame members that secure the joint to the limb. When actuated, the centre of rotation of the whole joint moves backwards in a similar manner as described in the anatomy of the human knee.

Thickness of the wire rope may be selected to alter the resistance to movement of the system, the smoothness of motion and the torsional stiffness of the joint. In some embodiments, the wire rope is predominately made from wound steel cable to form a rope, which may have high strength and stiffness compared to for example, synthetic fibres. The wire rope can be pulled under a load before being locked off, this creates preload in the system, which increases torsional stiffness and thereby efficiency. In doing so in combination with the rotational sensor being linked to the joint, accuracy and responsiveness of motion detection is improved.

As illustrated in Figure 8, a magnetoresistive sensor 84 is used to sense rotation of the joint. An at least dipolar magnet 71 is placed on the rotational axis of one of the rotatable drums 62, 63 or preferably within a shaft, such that it is mechanically isolated from the rotation of the rotatable drum itself. The orientation of the dipole magnet 71 may be such that some of the flux lines run along the plane of rotation of the joint. A magnetoresistive sensor 84 in the plane of rotation may then be able to detect relative rotation between the sensor 84 and the magnet 71. A field profile of the magnet 71 must be at least such that the flux vector field profile in the plane of rotation of the joint is non-uniform. As such, a dipolar field is preferred. However, other field profiles such as quadrupolar may provide an advantage in producing a more complex flux vector field profile and increasing the effective sensitivity of a magnetoresistive sensor to relative rotation. However, a magnetoresistive sensor appropriate for use with a quadrupolar magnet would need to be selected.

In the described embodiment, the sensor is mounted upon or otherwise mechanically coupled to a shaft such that it is able to measure a relative change in magnetic field orientation caused by a relative rotation of the shaft about the axis in which the dipolar magnet is located.

Figure 9 illustrates an exploded view of a first frame unit, as depicted in Figures 1 , 2, 3, 4 and 5. Each frame unit configured to conform to a user’s lower thigh comprises a conformable layer 94 and a rigid layer 95. The conformable layer 94 is constructed from a material that has a Shore hardness of from about 88A to 92A. In the illustrated embodiment, the conformable layer is made from Xencast PX90 resin. The rigid layer 95 is constructed from a material that has a Shore hardness of about 75D. In the illustrated embodiment, the rigid layer is formed from Renishaw Hand/vacuum casting resin 420. Not shown is a compliant layer made from a foam such as, but not limited to, memory foam, disposed medially from and attached to the conformable layer. The foam may be flexible polyurethane foam with a density of approximately 64 kg/m³. In an embodiment, the foam is Flex Foam-iT! IV foam. The layers are affixed to one another using an adhesive suitable for use bonding plastics or resins. In the illustrated embodiments, the adhesive is rubber infused adhesive Cyanocrylate. It will be appreciated that other adhesives suitable to bond plastics or resins may be used. This construction scheme applies to each of the conformable frame units of each module.

In the illustrated embodiment, the first frame unit located superior to a user’s knee comprises the rotation sensing assembly. In Figure 9, a structural member of the first frame unit 85 interfaces with a cogged rotatable drum 62 via an engagement formation 101 configured to engage with teeth 64 of rotatable drum 62. The first housing member is held in place via thrust washer 72 and push-on fastener 67. The magnetoresistive sensor 84 is mounted upon circuit board 91 which comprises at least one processor 102. Circuit board 91 is attached to structural member 85, second structural member 92 and housing portion 93 via fixings 96 and 97. The housing portion 93 is attached to the rigid layer 95 with an adhesive. In the illustrated embodiments, the adhesive is rubber infused adhesive Cyanocrylate.

It will be appreciated that other adhesives suitable to bond plastics or resins may be used.

Figure 11 illustrates an exploded view of a second frame unit, as depicted in Figures 1 , 2, 3, 4 and 5. Each frame unit configured to conform to a user’s upper calf comprises a conformable layer 113 and a rigid layer 112. The conformable layer 113 is constructed from a material that has a Shore hardness of from about 88A to 92A.

In the illustrated embodiment, the conformable layer is made from Xencast PX90 resin. The rigid layer 112 is constructed from a material that has a Shore hardness of about 75D. In the illustrated embodiment, the rigid layer is formed from Renishaw Fland/vacuum casting resin 420. Not shown is a compliant layer made from a foam such as, but not limited to, memory foam, disposed medially from and attached to the conformable layer. The foam may be flexible polyurethane foam with a density of approximately 64 kg/m³. In an embodiment, the foam is Flex Foam-iT! IV foam. The layers are affixed to one another using an adhesive suitable for use bonding plastics or resins. In the illustrated embodiments, the adhesive is rubber infused adhesive Cyanocrylate. It will be appreciated that other adhesives suitable to bond plastics or resins may be used. Optionally or additionally, an engagement formation such as a ‘clip’ may be disposed therebetween or formed integrally with one or both components to facilitate connection of the components with or without adhesive. This construction scheme applies to each of the conformable frame units of each module.

The structural member 111 is attached to the rigid layer 112 with an adhesive. In the illustrated embodiments, the adhesive is rubber infused adhesive Cyanocrylate. Optionally or additionally, an engagement formation such as a ‘clip’ may be disposed therebetween or formed integrally with one or both components to facilitate connection of the components with or without adhesive. It will be appreciated that other adhesives suitable to bond plastics or resins may be used.

The structural member 111 is formed with an engagement portion 114 which is configured to engage with teeth 64 of rotatable drum 63. The structural member is held in place via thrust washer 72 and push-on fastener 67.

In optional embodiments there are multiple other joint mechanical designs that could be appropriate for the module 11. Disclosed herein are examples of types of joints that could be implemented in a module 11 : Pivot

This is a single axis joint and is the most traditional form of suitable joint. It may consist of a bearing arrangement or the use of bushings. Hinges are the most common used for this kind of joint, but are not anatomically correct and may lead to injury or lack of comfort.

Compliant

A compliant joint would achieve the desired motion using a flexible material. Many soft fabrics allow for the knee bending. Many sports supports use tight compression material for this application.

No mechanical interfaces

The mechanical joints described in the foregoing have an incorporated rotational axis. However, it is possible to create a non-corporeal sensed joint with electronic sensors. In an embodiment, a virtual representation of the space that the user occupies is generated and coordinates in the representation are assigned values. Such sensors may then be able to reference the virtual representation via relative position measurements of one another or of another marker used to construct the virtual representation, to determine a rotational about an axis in real space.

Further description of the foregoing embodiments, and optional aspects and embodiments of the present disclosure are detailed in the following.

A further reason to have a mechanical joint, other than allowing biomechanical motion, is to enable the use of electronic sensors in measuring the rotation of the joint about an axis. The torsional stiffness of a mechanical joint provides stability, increasing accuracy of the data capture by providing a stable platform which enables consistent referencing. Sensors suitable for use in a sensed rotational axis may be: potentiometers; encoders; flex sensors; thin film potentiometers; hall sensors; and inductive position sensors.

In a particular embodiment, a magnetoresistive sensor used to detect rotation. The sensor may be a microchip that can read the polarity of a magnetic field from a magnet placed above it. This type of sensor requires no mechanical interface, therefore drastically reducing physical wear. A magnet may be mounted in a portion of a sensed joint 14, and the sensor mounted in a separate portion such that the rotation of the joint 14 translates to a relative rotation between the magnet and the sensor. In an embodiment, a module 11 requires attachment to the shin of a user. A fastening to a user’s shin functionally holds the lower half of the product tightly and securely but comfortably to the user, allowing for direct input from the shin moving about the knee axis. For example, as the shin is moved backwards the product stays in direct contact and position relative to the shin. This allows sensing of the joint 14 to occur, due to the relative rotation of the upper and lower halves of the leg.

The module may be more rigid in the sagittal plane, (the plane of the knee motion), while being flexible enough to comfortably conform to the user’s lower leg in other planes. This rigidity will help transfer the motion into the exoskeleton joint 14 of the module 11.

The second frame unit (shin frame) may comprise a frame component, an attachment strap, a latching system and mechanical connection to the joint and adjustable length component for the strap.

The frame may be conformed and comfortable to many users. This is achieved with a flexible material which can be arched into an appropriate shape. The attachment strap goes around the top of the calf muscle and is pulled tight by the user using an adjustable component. This configuration accommodates for multiple sizes and increases a user’s comfortability rating. The latching system will attach the strap back to the frame once it is wrapped around the calf.

The structure may be compliant to allow for other motions in the knee joint as stated previously. The structure may allow small ranges of motion which if prevented could potentially cause unforeseen damage.

The frame component for the shin may comprise 3 layers. A hard, rigid outer casing which connects to the joint 14, attached to this layer, a softer material which is compliant and flexible. This layer allows for the variation in user sizes but provides enough support for secure fitting. Inside this layer a soft form or fleece like material may be added, to increase skin to product comfort. The frame may be constructed from a plastic, resin, or polyurethane material. Particularly, the frame may be constructed from layers of resilient materials and conformable materials. The frame may be constructed from one, two, three or more layers of materials selected to be conformable or non-conformable in an optional arrangement. In an embodiment, the frame is constructed from of one or more of a resin, a plastic or a polyurethane material.

The first frame unit (thigh frame) is similar in functionality to the shin frame; however, it accommodates the electronics housing. The thigh frame may comprise a frame component, an attachment strap, a latching system and mechanical connection to the joint, adjustable length component for the strap and housing for electronics.

The mechanical connection to the joint 14 can be a variety of different options, for example, two pieces of metal or plastic bolted together. It could also comprise the joint 14 component, being moulded or otherwise integrally formed into the frame component at the manufacturing stage. An ascribed benefit of an exoskeleton is that the rigid links between the sensed joints 14 provides higher accuracy and better detail collection. A further ascribed benefit of rigid links is that feedback may be provided therethrough using actuators configured to give feedback to the user.

The frame may be flexible once again to conform to multiple user’s sizes, with an adjustable strap for attachment and comfort. The thigh frame may house the electronics by enclosing the PCB and also have the relevant USB ports open to the outside world.

The thigh frame may also have a LED light pipe, or simple LED lights, for conveying status indications of the module 11 to the user. This LED light pipe is located along the thigh frame, starting from the joint 14. This is due to the placement of the PCB. The LED may act as a visual indictor for the user to the state that the module 11 is in. For example, a steady green light for module 11 is working properly and is active.

A strapping system on the module is designed to be as comfortable as possible but provide a secure fastening system. To increase comfort the strap is likely to be elasticated, allowing for muscle contractions and user size variation. The strap may have a latching system on one end which secures to the frame. This allows for the module 11 to be put on by the user easily and quickly. Adjustment throughout can also be achieved by tightening or loosening the strap.

The shin strap may be deliberately placed over the top of the calf muscle. The bulging of the muscle may act as a wedge for the strap. As gravity tries to pull the product down the leg, the calf acts to prevent this motion by holding the calf strap in place. This is achieved by configuring the strap to pass over the bulk of the calf muscle as described in the foregoing.

The thigh strap may not prevent the module 11 from slipping down the leg in the same manner as the calf strap, therefore its functionality is to securely hold the thigh frame to the user. Again, this may be achieved using an elasticated strapping system which can be easily equipped and removed by the user.

The electronic architecture may comprise a PCB which has a microcontroller, a position sensor and an IMU (inertial measurement unit) on one leg module 11 , and a PCB with a position sensor and IMU on the other leg module 12.

The system 10 may only require one micro-controller to process and handle the data collection from all the sensors. The system 10 may require two micro controllers. In an embodiment there may be two micro-controllers, one in each leg module 11 , wherein the leg modules are connected wirelessly and the modules each comprise a wireless communication means such as a modem or other appropriate device.

A wireless configured arrangement would not have (for example) a USB cable providing connectivity to an external computing device, nor would it have a connecting cable between the two modules.

In a wired arrangement there may be a cable operable connecting the two devices, such a cable may be a rugged data cable, fixed into the thigh frame at the manufacturing stage. Such a cable may be fixed in such a way to prevent users from pulling out the cable or breaking it, inadvertently or otherwise. Such a cable is to be clipped to the user’s waist line to hold it out of the way during use, preventing potential trip hazards and loss of immersion by feeling the cable during use.

A cable between one or two modules in a system 10 and an external computing device may be a heavy duty USB data cable, or other heavy duty cable with an appropriate protocol. Depending on the user’s setup and brand of virtual reality headset, this cable can connected to an external computing device directly, or if the user has an HTC VIVE, into the 3rd party USB port in the headset, increasing the comfort of the product, due to less cable length.

A module 11 may also be fitted with an inertial measurement unit (IMU), which can sense accelerations and gyroscopic data. Many smartphones have these sensors built in. This sensor may be placed near the position sensor at the knee, but could be placed anywhere in the module. The measurements from this sensor allow for orientation tracking and pattern recognition of gait cycle, but the skilled person will recognise that data can be used for many more applications. These applications may be industry specific.

In some embodiments, software is used to run the device from an external computer. In some embodiments, software will output simple movements such as walking, running, turning on the spot, allowing these movements to simply control a game. To output these movements, data collected from the one or more sensors may be streamed to a remote computing unit. Optionally or additionally, pattern- recognition techniques may be used such as machine learning, Al, neural networks and decision trees.

In some embodiments, the system 10 will output raw movement and position data such that the direct movement of the leg can be analysed in medical or tracking applications, or directly used to represent the user’s leg in a virtual reality framework.

In some embodiments a haptic feedback element may give feedback to the user responsive to movement of the user. Such feedback may comprise a resistance to movement of an exoskeleton joint by engaging an actuator to one or more of: provide resistance to movement; vibrate the joint; and drive motion of the joint. In some embodiments, a haptic feedback element may comprise an actuator configured to provide a vibratory motion to the module. In some embodiments, a haptic feedback element provides feedback in response to conditions in a virtual environment. Suitable devices for providing haptic feedback include linear motors; translation motors; vibration motors; do geared motors; and ac motors. It will be recognised that other electrically powered actuators or mechanisms may also be suitable for providing haptic feedback.

The system 10 is initially provided to work in a virtual reality environment as a solution to the locomotion problem in the gaming industry. Particularly, in one embodiment, the system is configured for use when a user is within a delimited area that is small relative to the user’s movements. Such a use-case is referred to herein as ‘on-the-spot’.

In an embodiment, a user would walk, run, turn, jump etc. ‘on-the-spot’ - and these types of ‘on-the-spot’ movements would be interpreted by a game as walking or running, thereby enabling free roaming of a virtual environment with effectively infinite movement. In an embodiment, the user may move freely using an AR headset - and the leg movements would transfer to the AR environment to allow interaction with AR objects.

The primary function of the system 10 is to allow leg motion to be inputted into any game to control the player in a new or existing interaction. This could be but are not limited to walking or running, which are solutions to the locomotion problem. Optionally or additionally, it allows for motion such as, but not limited to, kicking a ball or tai chi movements. These are not possible in the current virtual reality setups because the leg position or movement is not captured.

A further ascribed benefit of the use of the module is that a user may not need to control locomotion within a virtual environment with their hands. Many games require the controllers for other functions such as grabbing, throwing or touching. With some of the software solutions to locomotion stated above, these functions of the hand are severely hampered.

The third function is to allow the user to move more naturally while in virtual reality, which will reduce the impact of motion sickness.

In the third instance, the user may wear the device at the knee, and the data would be live streamed to an external computing device for analysis, or captured on the device and analysed later.

Following is a list of possible applications for the module or kit of parts comprising two modules and system 10 disclosed.

Health care:

Within the field of physiotherapy, the method of measuring human range of motion is very crude. It is done by eye, by review of video images, or byusing an instrument such as a goniometer and/or the physiotherapist’s experience to judge whether someone has increased their range of motion, or the quality of that motion. A physiotherapist’s accuracy is about 5° which is 325,000 times less accurate than the position sensor disclosed. Using this device, a physiotherapist could perform repeatable and accurate range of motion, and quality of motion tests for patients undergoing rehabilitation therapy.

The module 11 or system 10 could data capture for dynamic movements such as a complete gait cycle. The setup of this product is also very simple and does not require an expert in motion capture marker placement, which in itself is highly objective and difficult to reproduce consistently.

Manufacturing and workers in hazardous environments:

The module 11 is capable of capturing live data constantly. As such, if a workforce wore this product, then a manager could monitor the safety of their workers by seeing they are active with normal movements, and not stationary, or lying down injured.

The module or system could also be used as a training device. Someone could be lifting heavy objects and if wearing this product, the data from the legs could tell if the worker has lifted the product safely with their legs and not using just their back.

Other environments in which the module or system may find applications according to the foregoing within include but are not limited to: firefighting; construction; rescue working; and military applications.

Film/TV:

The film industry heavily uses motion capture for movies requiring animation. To setup this kind of motion capture typically involves very sophisticated hardware and software costing large amounts of money and man hours. They are limited to the range of the camera sensors, which usually confines them to move in a lab environment and then use a green screen to add an environment into the background. With the disclosed module 11 in a wireless configuration, motion could be captured outside on any terrain and in any location. In the field of motion capture for visual media, techniques currently focus on capture of the surface of an actor and not capturing the motion of joints explicitly. It is an ascribed benefit of the present disclosure that joint motion may be captured and used for more accurate model creation controlling the internal skeleton of models, rather than the outer skin.

Sports analysis:

By the very nature of competitive sport, sport players are always trying to find a way of beating a competitor and this is done by hours of training. In an example use-case of the present disclosure, the module or system could be worn by an athlete and a sport coach could see the exact biomechanical difference in their player to a world class player. For example, a gold medallist cyclist could wear the device and cycle on a static bike, an average cyclist could then wear the device and compare knee flexion, speed of movement, orientation of leg etc., to the professional and increase their own output. A world class athlete could also fully analyse their own performance, repeating movements using the device, and analysing their results to maximise performance. It is an ascribed benefit of the module that data about the leg and joint motion could be captured rather than merely deriving such information from the motion of the pedals of a bike, as in the aforementioned example.

All references made herein to orientation (e.g. top, bottom, etc.) are made for the purposes of describing relative spatial arrangements of features, and are not intended to be limiting in any sense.

The scope of the present disclosure includes any novel feature or combination of features disclosed therein either explicitly or implicitly or any generalisation thereof irrespective of whether or not it relates to the claimed invention or mitigate against any or all of the problems addressed by the present invention. The applicant hereby gives notice that new claims may be formulated to such features during prosecution of this application or of any such further application derived therefrom. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in specific combinations enumerated in the claims.

Further aspects and embodiments of the invention are described by the following numbered clauses:

1. A module (11 ) for an exoskeleton comprising; a frame member configured for attachment about an anatomical joint of a limb of a user of the exoskeleton; a rotation sensing assembly configured to sense a rotation about a sensed rotational axis corresponding to an axis of rotation of the limb about an anatomical joint; a sensor module configured to sense an acceleration and an attitude of the limb; wherein, the module is configured to accommodate lateral and/or medial movement and/or rotation of the anatomical joint; so as to maintain conformity with the limb of the user during movement of the limb. A module according to clause 1 , wherein the rotation sensing assembly and/or sensor module comprise sensor circuitry and wherein the sensor circuitry is configured to be operatively coupled to a processor and/or a remote system. A module according to clause 1 or 2, wherein the module is configured to be attached to a left or right limb of a user. A module according to any preceding clause, wherein the frame member is configured to be compliant in the horizontal plane. A module according to any preceding clause, wherein the module is configured to accommodate lateral and/or medial movement and/or rotation of the anatomical joint in the horizontal plane. A module according to clause 5, wherein the frame member is configured to have a greater stiffness in a first plane than in a second plane. A module according to any preceding clause, further comprising a data communications (16) member configured to provide data communications between the module (11) and a second module (12). A module according to any preceding clause, wherein the rotation sensing assembly and/or sensor module are configured to further sense at least one or more of: a. acceleration; b. location; c. position; d. orientation; e. force; f. speed; g. velocity; h. angular velocity; i. angular displacement; j. angular acceleration; k. torque;

L. impulse; m. rotation; and n. momentum. A module according to any preceding clause, wherein the module comprises at least one pivot configured to accommodate the lateral and/or medial movement of the anatomical joint. A module according to any preceding clause, wherein the sensed rotational axis is formed by an exoskeleton joint (14) comprising one or more of: a pivot joint; a polycentric joint; and a compliant joint. A module according to clause 10, wherein the frame member comprises a first frame unit 13 beatable superior to the anatomical joint and a second frame unit beatable inferior 14 to the anatomical joint, and wherein the first and/or second frame units are configured to attach to a lateral limb position and/or a medial limb position. A module according to clause 11, wherein the exoskeleton joint (14) is integrally formed with at least one of the first frame unit and/or second frame unit. A module according to any preceding clause, wherein the frame member comprises a layered structure comprising one or more layers. A module according to clause 13, wherein the layered structure comprises an outer layer and a compliant layer; or wherein the layered structure comprises an outer layer, an inner layer, and a compliant layer disposed therebetween. A module according to clause 14, wherein the outer layer is more rigid in the plane of rotation of the exoskeleton joint than in a plane normal to the plane of rotation of the exoskeleton joint, and is conformable in the plane normal to the plane of rotation of the exoskeleton joint. A module according to any of clause 11 to 15, wherein at least a portion of the rotation sensing assembly and/or sensor module are located proximate to and/or disposed within the first frame unit. A module according to any preceding clause, further comprising at least one power source member configured to power one or more of: the rotation sensing assembly; and/or the sensor module. A module according to any preceding clause, wherein the rotation sensing assembly is coaxially aligned with at least a portion of the sensed rotational axis. A module according to any preceding clause, wherein a first sensor of the rotation sensing assembly is configured to be mechanically isolated from the sensed rotational axis. A module according to any preceding clause, wherein the rotation sensing assembly comprises a reference element coaxially aligned with a first sensor of the rotation sensing assembly and the sensed rotational axis; and the first sensor of the rotation sensing assembly senses rotation of the reference element relative thereto. A module according to clause 20, wherein the reference element is a magnet. A module according to any preceding clause, wherein the module further comprises a haptic feedback element. A module according to any of clauses 6 to 22, wherein the first plane is the sagittal plane and the second plane is the horizontal plane. A kit of parts comprising, a first module according to any of clauses 1 to 23; and a second module according to any one of clauses 1 to 23. A kit of parts according to clause 24, wherein the first or second module comprise a module configured to be attached to a left limb of a user and the other module comprises a module configured to be attached to a right limb of a user. A method of directly detecting movement of a limb of a user, comprising the steps of: a. sensing at least one rotation of the limb about an anatomical joint with at least a rotation sensing assembly ; b. sensing acceleration and attitude of the limb with at least one sensor module; and c. transmitting the rotation, acceleration and attitude to a processor and/or a remote system, wherein the processor and/or the remote system is configured to quantify a displacement and/or arrangement of the limb. A method according to clause 26, further comprising attaching a first module according to any of clauses 1 to 23 to the limb of the user about the anatomical joint; and conforming a portion of the module to the user’s limb; wherein the module is a first module configured to be attached to a left or right limb of the user. A method according to clause 26 or 27, further comprising: a. attaching a second module according to any of clauses 1 to 23 to a second limb of the user about a second anatomical joint; b. sensing at least one rotation of the portion of the second limb about the second anatomical joint with at least a rotation sensing assembly of the second module; c. sensing acceleration and attitude of the second limb with at least one sensor module of the second module; and d. transmitting the rotation, acceleration and attitude of the second limb to a processor and/or a remote system, wherein the processor and/or the remote system is configured to quantify a displacement and/or arrangement of the second limb. A method according to clause 28, wherein the first or second module comprise a module configured to be attached to a left limb of a user and the other module comprises a module configured to be attached to a right limb of a user. A method according to any one of clauses 26 to 29, wherein the processor is further configured to control a virtual element within a virtual, augmented or mixed reality framework, compute an equivalent displacement of the virtual element, and update the virtual, augmented or mixed reality framework to reflect the displacement and/or arrangement of the or each limb. A method according any one of clauses 26 to 30, wherein the processor is further configured to calculate a rate of displacement of at least one of the first and/or second limb from the computed displacement and/or arrangement of the first and/or second limb and wherein at least one velocity is inferred from the rate of displacement and assigned to at least one element within the virtual, augmented or mixed reality framework. A method according to clause 31 , wherein the rate of displacement of the first and/or second limb is responsive to one or more of; a. jumping; b. running; c. squatting; d. side stepping; e. strafing; f. walking; g. hopping; h. spinning; i. skipping; j. cantering; k. stretching.

Claims

Claims:

1. A polycentric joint for an exoskeleton device or system comprising: a first rotatable drum having a first engagement portion; a second rotatable drum having a second engagement portion; and a flexible filamentary member engaged with the first engagement portion and extending therefrom to engage with the second engagement portion, wherein the first and second rotatable drums are configured to rotate about two adjacent respective first and second axes, such that a proportion of the filamentary member engaged with the first or second engagement portions is minimised.

2. A polycentric joint according to claim 1, wherein the flexible filamentary member is configured to trace at least a partial lemniscatic path running about the first rotatable drum and the second rotatable drum.

3. A polycentric joint according to claim 2, arranged such that an incident torque upon the first engagement portion develops an equivalent torque upon the second engagement portion via the lemniscatic arrangement of the flexible filamentary member.

4. A polycentric joint according to claim 3, wherein the first and second rotatable drums are arranged within a respective first and second support portion, configured to allow rotation of the rotatable drums and passage of the flexible filamentary member.

5. A polycentric joint according to claim 4, wherein a rotation sensor assembly is arranged to sense relative motion between the first or second rotatable drum and the first or second support portion.

6. A polycentric joint according to claim 5, wherein the first support portion is opposed to the second support portion and offset in the first plane from the second support portion.

7. A polycentric joint according to claim 6, wherein the first support portion is aligned with the second support portion and offset in the first plane from the second support portion.

8. A polycentric joint according to claim 7, wherein the support member comprises at least one friction reduction member disposed between an outer surface of at least one first upstanding member and an inner surface of the first rotatable drum and at least one friction reduction member disposed between an outer surface of at least one second upstanding member and an inner surface of the second rotatable drum.

9. A polycentric joint according to claim 8, wherein the at least one friction reduction member comprises one or more of: a bushing; one or more bearings; and/or a lubricant.

10. A polycentric joint according to claim 9, wherein the first and/or second upstanding member each comprise at least one magnet; and wherein the at least one magnet is coaxially aligned with a respective one of the first and/or second axis, and wherein the magnet forms part of the rotation sensing assembly.

11. A polycentric joint according to claim 9, wherein at least one of the first and/or second rotatable drum comprise at least one magnet located on an upper surface and coaxially aligned with the respective first and/or second axis, and wherein the magnet forms part of the rotation sensing assembly.

12. A polycentric joint according to claim 10 or 11, wherein the poles of the at least one magnet are perpendicular to the first and/or second axis.

13. A polycentric joint according to any preceding claim, wherein the flexible filamentary member is configured in a figure of eight arrangement around the first and second rotatable drum and the flexible filamentary member comprises at least two cross overs at a point disposed between the first and second rotatable drums.

14. A polycentric joint according to claim 13, wherein a rate and/or a range of the rotation of the first rotatable drum is substantially equal to a rate and/or a range the rotation of the second rotatable drum.

15. A polycentric joint according to any preceding claim, wherein the first rotatable drum and the second rotatable drum have a range of rotation of at least about 120° in a clockwise and/or anticlockwise direction.

16. A polycentric joint according to any preceding claim, wherein a first and/or second end of the flexible filamentary member terminates proximal to the first rotatable drum.

17. A polycentric joint according to any of claims 1 to 15, wherein a first and/or second end of the flexible filamentary member terminates proximal to the second rotatable drum.

18. A polycentric joint according to any of claims 1 to 15, wherein a first end of the flexible filamentary member terminates proximate to the first or second rotatable drum and a second end of the flexible filamentary member terminates proximate to the other rotatable drum.

19. A polycentric joint according to any preceding claim, wherein the first and/or second end of the flexible filamentary member is configured to terminate internal to the engagement portion of the first and/or second rotatable drum.

20. A polycentric joint according to any preceding claim, wherein the flexible filamentary member is configured to apply a force via the first and second engagement portions to inhibit individual rotation of the first rotatable drum, the second rotatable drum and/or the flexible filamentary member.

21. A polycentric joint according to any preceding claim, comprising two flexible filamentary members.

22. A polycentric joint according to any preceding claim, wherein the first and second engagement portions trace respective rotation profiles in a ratio of substantially 1:1 to each other.

23. A polycentric joint according to claim 22, wherein the rotation sensing assembly further comprises a sensor configured to sense a rotation of the at least one magnet relative to the sensor.

24. A polycentric joint according to claim 23, wherein the sensor is a magnetic resistive sensor.

25. A polycentric joint according to claim 23 or 24 dependent upon claim 10, wherein the at least one sensor is located on an upper surface of the first and/or second rotatable drum.

26. A polycentric joint according to claim 23 or 24 dependent upon claim 11, wherein the at least one sensor is located internal to at least one of the first and/or second upstanding member.

27. A polycentric joint according any of claims 5 to 26, further comprising at least one processor operably linked to the rotation sensing assembly to receive data therefrom.

28. A polycentric joint according to any of claim 5 to claim 27, further comprising at least one further sensing assembly configured to sense one or more of: a. acceleration; b. location; c. orientation; d. force; e. speed; f. velocity; g. angular velocity; h. angular displacement; i. angular acceleration; j. torque; k. impulse;

L. rotation; m. momentum; and/or n. temperature.

29. A polycentric joint according to claim 28, wherein the at least one further sensor assembly is operably linked to at least one processor.

30. A polycentric joint according any of claims 27 to 29, wherein the at least one processor and/or at least one further processor comprise at least one connection member configured for physical and/or wireless connection with a computing device.

31. A polycentric joint according any preceding claim, further comprising at least one actuator configured to actuate rotation of at least one of the first and/or second rotatable drum.

32. A polycentric joint according any preceding claim, wherein each of the first and/or second rotatable drum comprise at least attachment portion configured for attachment of one or more frames.