Insufficient actuation of the distal joints of the shoulder exoskeleton and the transmission constraint reaction device

Abstract

An underactuated mechanism (I) allows actuation of the distal degrees of freedom of the shoulder joint and transmission of torque and reaction forces, the drive system on the frame (3) being formed with the trunk (5) through a super-redundant motion mechanism (200) as follows: a. a first non-actuated rotary joint (100) connected to the human trunk (5), which rotates around the axis X, b. a connection mechanism (200) connected to the first rotary joint (100), c. a second rotary joint (300), which (i) rotates around the Y axis, arranged according to the degree of flexion and extension of the shoulder joint coplanar with the X axis, and (ii) is composed of a driven pulley and a Bowden pulley. A remote drive cable or a direct drive actuation system with co-located motors, (ili) fixed on one side to a connection mechanism (200) and on the other side to a human arm (6), the connection mechanism (200) comprising: at least three or more members (210, 220, 231), two of which (210, 220) are rigidly fixed to one of the rotational joints (100, 300), each having parallel joints, referred to as minimum joints A and B, arranged to connect one member to the next to form a rotational constraint around the axis of the parallel joints.

Description

Technical Field

[0001] The invention relates to the technical field of upper limb exoskeletons for strengthening and assisting patients with upper limb movement disorders, and in particular to a system suitable for transmitting shoulder joint flexion and extension torque. Background Art

[0002] The present invention is applied to the fields of rehabilitation medicine and human enhancement in the industrial field.

[0003] In the industrial field, in order to reduce and prevent the occurrence of musculoskeletal system pathologies caused by overload work in performing repetitive tasks and load transportation, and to reduce muscle fatigue in repetitive tasks, wearable support devices of the exoskeleton type (passive or robotic type) have become popular, capable of transferring the forces required to perform tasks from the distal areas of the upper limbs to body areas such as the trunk or legs, bypassing the load and transferring it to the waist area.

[0004] In the field of medical rehabilitation, exoskeletons are often used for robotic-assisted rehabilitation.

[0005] In the field of rehabilitation robots and upper limb collaborative robots, they are generally divided into two categories: end-effector-based robots (EEB Robots) and exoskeleton robots.

[0006] The interaction between the EEB robot and the human body takes place only through the end effector, which is in contact with the patient's hand or forearm. The arm is spatially positioned and / or oriented according to the degrees of freedom available to the mechanism. Generally speaking, the axes of rotation of the joints of the robotic system do not coincide with those of the human joints: this is why EEB robots are easier to design and manufacture than exoskeletons and are also easier to adjust to the different lengths of patients' arms.

[0007] In contrast to these advantages, knowing the robot’s posture, the posture of the arm and / or the torques at the human joints cannot be uniquely determined, and in fact, the interaction between the robot and the human takes place through only one contact point.

[0008] Then, there is the real transition from EEB to exoskeleton. Upper limb exoskeleton is a mechanism that is kinematically isomorphic to the arm, with the axes of the mechanical joints aligned with the axes of the human joints.

[0009] An exoskeleton is essentially a mechanical structure parallel to the arm. This property allows exoskeleton devices to have multiple connection points (interfaces) between human and robot: more interfaces are able to accurately determine the posture of the human limb from the posture of the robot. The same applies to the torques at the human joints, which can be determined and monitored one by one. By using mechanical stops at the joints, unwanted phenomena such as hyperextension of the elbow can be avoided. Because the exoskeleton has similar kinematics to the upper limb, it is usually possible to cover most of the workspace that can be reached by the human arm with the exoskeleton: However, this requires adjusting the link length to the arm length.

[0010] The most important aspects to consider when designing an exoskeleton for the upper limb include:

[0011] The shoulder rotation center is not fixed: The shoulder rotation center moves during flexion and extension, abduction and adduction movements. If the exoskeleton is also attached to the body at the forearm. The movement of the rotation center must be taken into account to eliminate errors caused by misalignment between the robot joint axis and the shoulder axis.

[0012] A single configuration of the robot shoulder joint should not be within the robot workspace, or should be at its boundaries.

[0013] Placing the robot shoulder joint axis over the human shoulder’s center of rotation is an operation that cannot be performed precisely and needs to be repeated for each patient.

[0014] The inertia of moving parts should be low to have good mechanical transparency.

[0015] The security of your equipment is of paramount importance.

[0016] In [1], the joint misalignment problem is discussed, i.e., the difficulty in obtaining active robot joint axes that are properly aligned with human joint axes.

[0017] Due to the hyperstatic nature of the human-plus-robot system, unwanted arm movements may occur, with the potential for unnecessary stress on the human body. In fact, in case of misalignment, if both kinematic chains were rigid, the movement would be completely blocked. In practice, misalignment is restored by deformation. The main deformations of the human-plus-robot system occur at the interface between the human and the robot, due to the lower stiffness of the skin, fat cells and muscle structure compared to the exoskeleton material. This is why, in case of joint misalignment, unnecessary stress is exerted on the human-exoskeleton interface.

[0018] To avoid this problem, among the methods that have been used, one can 1) insert elasticity and compliance into the exoskeleton, or 2) add redundant passive joints in the kinematic chain, or 3) use adjustable-length links or other calibration correction mechanisms, or 4) use interfaces between the exoskeleton and the human body's passive joints to avoid unnecessary stress.

[0019] As the interface area changes, the load is transferred between the robot and the person, and a slightly extended interface may be uncomfortable if the interface transmits torque, so it is recommended to use the widest possible interface or use pairs of interfaces at most.

[0020] Therefore, in recent years, flexible wearable robotic devices featuring flexible links or made entirely of light have been introduced. Flexible materials, such as fibers typical of textile fabrics or composite materials, have been introduced. Kobayashi and Hiramatsu of the University of Tokyo studied the first flexible robot for assistive arms.

[0021] The system consists essentially of a fabric suit that acts as a second skin over the torso and arms. McKibben-type pneumatic actuators are attached to the suit and function much like human muscles, i.e. they contract to reduce the distance between two points on the suit.

[0022] Conor Walsh of Harvard University subsequently studied pneumatically driven flexible wearable devices. The basic concept is the same as the muscle suit of the University of Tokyo, that is, using air chambers as an external muscle system. As for the upper limbs, Professor Walsh basically made two devices, one for the hand and one for the shoulder [2-3].

[0023] Lorenzo Masia et al. from NTU University, Singapore developed an exosuit (soft wearable exoskeleton) for the elbow [4, CN107921628] consisting of two fabric interfaces that can be closed around the arm with Velcro straps. One of the interfaces is placed on the forearm and one on the arm. Two cables are inserted between the two interfaces, which act as two antagonist muscles, the biceps and triceps. The cables are fixed between the two interfaces and are guided by motors located in a back pack with Bowden cable transmission (sheathed cables).

[0024] There are also many exoskeletons among the most advanced technologies.

[0025] Most of the solutions provided in the literature refer to those using rigid exoskeleton structures to transmit forces and motions.

[0026] In US2019160653, a parallel motion system for actuating the shoulder joint by a mechanism actuated by 3 linear actuators is described, and in W02018093448, a motion mechanism with a remote center of rotation and rigid link spherical motion is described.

[0027] Some of these systems are dedicated to supporting the lower limbs and use pneumatic drives (US2019029914) or belt systems suitable for transmitting tension upwards (CN108670195, US2018008502). CN107921628 uses Bowden cables and applies the same concept, providing a solution suitable for transmitting auxiliary torque to the elbow.

[0028] In CN109318217A, a Bowden cable actuation system was patented using actual pulleys mounted on a rotating pair with vertical inclination for actuating the flexion / extension or abduction / adduction joint of the shoulder joint, but this system does not allow full movement of the shoulder joint.

[0029] In WO2019081851, an articulated, flexible parallelogram mechanism is described that allows positioning of an axis of actuation in alignment with the degrees of freedom of the wearer's shoulders.

[0030] In contrast, in ITUA 20164364A1, a system for transmitting rotational motion between two arbitrary pulleys arranged on a spatial axis having an arbitrary spatial direction is provided.

[0031] The following references describe some mechanisms of shoulder exoskeleton transmission:

[0032] [1]H.Kobayashi,K.Hiramatsu,Development of muscle suit for upperlimb.Proceedings of the IEEE International Conference on Robotics&Automation,2004.

[0033] [2]P.Polygerinos,Z.Wang,KCGalloway,RJWood,CJWalsh,Soft robotic love for combined assistance and at-home rehabilitationRobotics andAutonomous Systems,2015,No.73,135-143

[0034] [3]CTO'Neill, NSPhipps, L.Cappello, S.Paganoni, CJWalsh, Asoftwearable robot for the shoulder: design, characterization, and preliminary testing. International Conference on Rehabilitation Robotics, 2017

[0035] [4] YGKim, M. Summary of the invention

[0036] The object of the present invention is to design and provide an underactuated mechanism which allows to meet the above requirements and at least partially overcome the above disadvantages with reference to the background art.

[0037] In particular, an object of the invention is to provide an underactuated mechanism for a robotic shoulder exoskeleton adapted to transmit the flexion-extension reaction forces generated during actuation of the shoulder joint through an actuator located at the level of the flexion-extension shoulder, through a flexible kinematic hyper-redundant system capable of overcoming the abduction-adduction degrees of freedom of internal and external rotation and transferring the actions on the trunk of the person wearing the system, thus articulating in the configuration and orientation of the arm, allowing the human greater freedom of movement.

[0038] Another object of the present invention is to provide an underactuated mechanism for a shoulder exoskeleton that is capable of correctly and automatically adjusting the alignment of the axes of the active robot joints with the axes of the human joints.

[0039] These and further objects and advantages are achieved by an underactuated mechanism for a shoulder exoskeleton and a shoulder exoskeleton comprising said underactuated mechanism according to the independent claims.

[0040] Further objects, solutions and advantages are found in the embodiments described below and are claimed in the dependent claims.

[0041] In particular, its kinematic structure is characterized by a proximal passive annular joint and a distal active annular joint, and the present underactuated mechanism allows to be connected through a hyper-redundant mechanism to create an upper limb exoskeleton with sufficient degrees of freedom to carry out movements related to the shoulder joint, equivalent to 3 independent degrees of freedom, without limiting the freedom of movement. The greater degrees of freedom of the above-mentioned hyper-redundant mechanism connecting the two annular joints also allow the entire underactuated mechanism forming the exoskeleton to have greater degrees of freedom for reconfiguration, so that it is able to automatically align and compensate for the movement of the shoulder's center of rotation and any assembly errors. This underactuated mechanism also has the characteristic of always keeping the distal annular joint aligned with the flexion-extension axis of the shoulder, thereby allowing the lifting of the arm to be assisted by a single motor or drive system at all times. Finally, the special kinematic structure of the above-mentioned underactuated mechanism allows the reverse transmission of reaction torque because there are no kinematic constraints between the distal annular joint, the hyper-redundant kinematic mechanism, and the proximal annular joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Some embodiments of the present invention will be described below by way of non-limiting examples with reference to the accompanying drawings, in which:

[0043] Figure 1 is an isometric view of the underactuated mechanism of the present invention, showing the three main modules constituting the present invention, namely, a rotation mechanism that, once actuated, can transmit flexion-extension torque action, a flexible element for torque transmission, and a rotation mechanism that is integral with the human torso;

[0044] Figure 2a and 2b The implementation details of the transmission system or super-redundant motion mechanism for transmitting torque are shown for the example cases of two components and four components respectively;

[0045] Figure 3 and Figure 4 Shows include Figure 1 Two possible configurations of the underactuated shoulder exoskeleton. DETAILED DESCRIPTION

[0046] With reference to the accompanying drawings, an underactuated mechanism according to the present invention, particularly an underactuated mechanism for a robotic exoskeleton, is generally represented by (underactuated structure 1).

[0047] The underactuated mechanism 1 can drive the distal degrees of freedom of the shoulder joint through the super redundant motion mechanism 200 and transmit the torque and reaction force generated by the drive system on the frame 3 or the trunk connection device (integrated with the trunk), which is formed as follows:

[0048] a. A first annular joint 100, connected or adapted to be connected to a human torso 5 rotating about the X-axis

[0049] b. Super redundant motion mechanism 200 connected to the first annular joint 100

[0050] c. The second circular or annular joint 300 (i) is arranged or adjusted to rotate around the Y-axis according to the degree of flexion and extension of the shoulder joint, coplanar with the Y-axis, and (ii) is remotely driven by a driven pulley and bowden cable or a direct drive drive system with a co-located motor. (i) The super-redundant motion mechanism 200 consists of at least three or more components 210, 220, 231, two of which 210, 220 are respectively firmly fixed to one of the annular joints 100, 300, all of which have parallel joints, called minimum joints A and B, arranged to connect one component to the next component to form a rotation constraint around the axis of the parallel joints.

[0051] Meanwhile, underactuation mechanism 1 includes:

[0052] a first annular joint 100, adapted to be connected to the human torso 5, wherein the first annular joint 100 defines a first joint rotation axis X;

[0053] b. A super-redundant motion mechanism 200 connected to a first annular joint 100 at a first end of the super-redundant motion mechanism 200

[0054] c. A second annular joint 300, which is suitable for connection to the human arm 6, the second annular joint 300 defines a second joint rotation axis Y, which is suitable for arrangement according to the degree of flexion and extension of the human shoulder joint, and the second annular joint 300 is connected to the super-redundant motion mechanism 200 at the second end of the super-redundant motion mechanism 200;

[0055] The underactuated mechanism 1 is configured to transfer the reverse torque and the reaction force from the second annular joint 300 to the first annular joint 100,

[0056] in:

[0057] - The first joint rotation axis X is coplanar with the second joint rotation axis Y;

[0058] - the first annular joint 100 is not actuated;

[0059] - the second annular joint 300 is driven in the following ways: remotely by a driven pulley and Bowden cable, or by a direct drive drive system with a co-located motor;

[0060] -The super-redundant motion mechanism 200 includes at least three components 210, 220231, which are connected together by an annular joint, and the axes are parallel to each other A, B, F, wherein one component 210220 of the at least three components is fixed on the first annular joint 100, and another component of the at least three components 210220 is fixed on the second annular joint 300.

[0061] Thus, the hyper-redundant kinematic mechanism 200 allows the shoulder to passively rotate about an axis X perpendicular to the axes Y and Z and is capable of transmitting a constraint reaction force perpendicular to the axis X and a constraint reaction force along the axis X without any relative rotation between the members forming the chain.

[0062] Furthermore, the hyper-redundant motion mechanism is capable of changing the distance between the first annular joint 100 and the second annular joint 300 by reconfiguring the relative rotation between adjacent components.

[0063] According to one embodiment, only the second annular joint 300 is driven.

[0064] A direct drive drive system with a co-located motor means that the motor is integrated in the second annular joint 300 or the second annular joint 300 is mounted directly on the output shaft of the motor.

[0065] According to one embodiment, the underactuated mechanism 1 for a shoulder exoskeleton lacks a forward kinematic transmission of rotational motion from the first annular joint 100 to the second annular joint 300. That is, the rotation of the second annular joint 300 around the second joint axis does not affect the rotation of the first annular joint 100 around the first joint axis.

[0066] According to such an embodiment, the underactuated mechanism 1 merely transmits the restraining reaction force from the second annular joint 300 back to the first annular joint 100 .

[0067] Within the scope of the present invention, an underactuated system is assumed, in which the multi-degree-of-freedom mechanism drives only the last degree of freedom: moreover, no torque transmission between the two axes is required, since the distal axis is considered to provide its own drive either through a remote drive system via a bowden or pneumatic cable, or on-site (direct drive) via an actuator located on the joint.

[0068] "Underactuated" refers to a mechanism that actuates fewer degrees of freedom relative to the total degrees of freedom.

[0069] At the same time, the mechanism 1 is underactuated, since between the first annular joint 100 and the second annular joint 300 , one of the two annular joints is not actuated, in particular the first annular joint is not actuated.

[0070] A “non-driven annular joint” is a system consisting of two bodies that are free to rotate about an axis and are not equipped with a rotating motor or other system capable of applying any value of torque between the two parts, while a “driven annular joint” is a system consisting of two bodies that are free to rotate about an axis and are equipped with a rotating motor or other driving system capable of applying any value of torque between the two sides.

[0071] A "super-redundant motion mechanism" refers to a series mechanism whose total degrees of freedom are much greater than the degrees of freedom of the rigid end bodies of the mechanism.

[0072] A "series mechanism" is a mechanism consisting of rigid bodies connected in series. There is at least one joint between two rigid bodies, allowing relative motion between the two rigid bodies with at least one degree of freedom.

[0073] A “robotic shoulder exoskeleton” is a wearable mechanism external to the human skeleton that follows the kinematic structure of the human skeleton and is connected to the human body at one or more points.

[0074] The first annular joint 100 is preferably arranged at a position closer to the human body trunk than the second annular joint 300 .

[0075] Therefore, the first annular joint 100 may be defined as a proximal annular joint and the second actuation annular joint 300 may be defined as a distal annular joint.

[0076] Meanwhile, the one of the at least three components 210 is disposed at a first end of the hyper-redundant motion mechanism 200 , and the other one of the at least three components 210 is disposed at a second opposite end of the hyper-redundant motion mechanism 200 .

[0077] According to one embodiment, the hyper-redundant motion mechanism 200 forms a rigid chain consisting of at least three different components 210 or rigid elements, connected together along axes a, B, D, . . . by rigid shafts 240 and spacers 230 via coplanar rotation couplings.

[0078] According to one embodiment, the at least three members 210 are rigid elements connected together sequentially or in series to form a chain.

[0079] According to one embodiment, each of the at least three components 210 is connected to a subsequent component by two relatively connecting spacer elements 230 of elongated shape and parallel to each other, and each of the connecting spacer elements 230 is respectively engaged with each component 210 and the subsequent component in rotation around two of the parallel axes of the annular joint.

[0080] According to one embodiment, the underactuated mechanism 1 comprises elastic balancing means allowing the second annular joint 300 to reach an equilibrium position relative to the first annular joint 100 determined by a minimum value of elastic and gravitational potentials.

[0081] For example, the elastic balancing device includes an elastic element connected to at least two of the at least three components 210 , or an elastic element connected to the first annular joint 100 and / or the second annular joint 300 and / or to at least one of the at least three components 210 .

[0082] For example, the elastic balancing device comprises a metal foil or other elastic material, such as carbon fiber, which has preferential elasticity in one plane and high stiffness in the other two directions.

[0083] In other words, it is also possible to provide the system with inherent elasticity through the system of elastic elements, so that the chain reaches an equilibrium position determined by the minimum values ​​of the elastic and gravitational potentials.

[0084] In alternative embodiments, the same restraint may be achieved with metal foil or other materials (such as carbon fiber) that have preferential elasticity in one plane and high stiffness in the other two directions.

[0085] In other words, the hyper-redundant connection device 200 may be equipped with a distributed inherent elastic system to achieve a balanced configuration without external forces other than its weight.

[0086] According to another aspect of the present invention, the above objects and advantages are achieved by a robotic shoulder exoskeleton 2 comprising an underactuated mechanism 1 according to the above features.

[0087] Specifically, the exoskeleton may include a first torso connection device 3 connected to the first ring joint 100, configured to fix the under-actuated mechanism 1 to the human torso 5, and a relative second arm connection device 4 connected to the second ring joint 300, configured to fix the under-actuated mechanism 1 to the human arm 6.

[0088] The shoulder exoskeleton described above is able to independently compensate for any misalignment between the human joints and the exoskeleton joints with the aid of the hyper-redundant motion mechanism 200 .

[0089] The shoulder exoskeleton described above has the farthest rotational degree of freedom and is able to provide assistive torque to the wearer.

[0090] Although the above-described underactuated mechanism 1 has been demonstrated to be applicable to the shoulder joint of the upper limb, it can also be applied to the knee joint of the lower limb without substantial modification.

[0091] Similarly, although a robotic shoulder exoskeleton for the upper extremities has been described, such an exoskeleton could be a robotic knee exoskeleton for the lower extremities without substantial modification.

[0092] Those skilled in the art may modify and adapt the embodiments of the above-described devices, or replace components with other functionally equivalent components, to meet or meet the needs without departing from the scope of the following claims. Each feature described as belonging to a possible embodiment can be implemented without considering the other embodiments described.

Claims

1. An underactuated mechanism, which allows remote actuation of the distal degrees of freedom of a human shoulder joint by bypassing a passive non-actuated first rotational joint (100), and allows the reaction torque and force generated by the drive system on a frame (3) fixed to a trunk (5) to be transmitted backwards, To this end, the underactuated mechanism is composed of a super-redundant kinematic mechanism (200), specifically comprising: a. a non-driven first rotation joint (100) connected to the human torso (5) and rotating about the X-axis, b. a connection mechanism (200) connected to the first rotary joint (100), c. A second rotary joint (300) which (i) rotates about a Y axis arranged according to the degree of flexion and extension of the shoulder joint and is coplanar with the X axis, (ii) is remotely driven by a driven pulley and a Bowden cable, or by a direct drive system with a co-located motor, and (iii) is fixed to a connection mechanism (200) on one side and connected to a human arm (6) on the other side, the connection mechanism (200) comprising: at least three or more components (210, 220, 231), wherein two components (210, 220) are rigidly fixed to one of the annular joint rotary joints (100, 300), all of which have parallel joints, called minimum joints A and B, arranged to connect one component to the next component to form a rotation constraint around the parallel joint axis; wherein the co-located motor is integrated in the second rotary joint (300).

2. The underactuated mechanism according to claim 1, wherein only the second rotational joint (300) is driven.

3. The underactuated mechanism according to claim 1, wherein the motor located at the same position is integrated in the second rotary joint (300).

4. The underactuated mechanism according to claim 1, wherein the underactuated mechanism (1) has no forward kinematic transmission of the rotational motion from the first rotational joint (100) to the second rotational joint (300).

5. The underactuated mechanism according to claim 4, wherein the underactuated mechanism (1) is configured to transmit only the constrained reaction force from the second rotational joint (300) backward to the first rotational joint (100).

6. The underactuated mechanism according to claim 1, wherein the first rotational joint (100) is closer to the human body trunk (5) than the second rotational joint (300).

7. The underactuated mechanism according to claim 1, wherein one of the at least three components (210) is arranged at a first end of the super-redundant connection mechanism (200), and another of the at least three components (210) is arranged at an opposite second end of the super-redundant connection mechanism (200), and is respectively connected to the first and second rotation joints, and the displacement of the mechanism is limited within a plane orthogonal to the axes of the first and second rotation joints.

8. The underactuated mechanism of claim 1, wherein the super-redundant super-redundant motion mechanism (200) forms a rigid chain consisting of at least three different components (210) or rigid elements, connected together along axes a, B, D, ... by a coplanar rotating coupling through a rigid shaft (240) and a gasket (230).

9. The underactuated mechanism according to claim 1, wherein the at least three members (210) are rigid elements connected together in sequence or in series to form a chain.

10. The underactuated mechanism of claim 1, wherein each of the at least three members (210) is connected by two opposing elongated spacer elements (230). Connected to the subsequent components and parallel to each other, each of the connecting spacer elements (230) is rotatably engaged with each of the components (210) and the subsequent components, which are respectively located near two of the parallel axes of the rotary joint.

11. The underactuated mechanism according to claim 1, comprising an elastic balancing device, which allows the second rotary joint (300) to reach an equilibrium position relative to the first rotary joint (100), the equilibrium position being determined by the minimum value of the elastic potential and the gravitational potential.

12. The underactuated mechanism according to claim 11, wherein the elastic balancing device comprises an elastic element connected to at least two of the at least three components (210), or connected to the first rotary joint (100) and / or the second rotary joint (300), and / or connected to at least one of the at least three components (210).

13. The underactuated mechanism of claim 11, wherein the elastic balancing means comprises a metal foil or other elastic material having preferential elasticity in one plane and high stiffness in the other two directions.

14. The underactuated mechanism (1) according to claim 1, wherein the super-redundant connection device (200) is equipped with a distributed intrinsic elastic system to achieve a balanced configuration in the absence of external forces other than weight.

15. The underactuated mechanism of claim 1, comprising: A. A first rotation joint (100), adapted to be connected to a human body trunk (5), wherein the first rotation joint (100) defines a first joint rotation axis X; B. a hyper-redundant motion mechanism (200) connected to a first rotation joint (100) at a first end of the hyper-redundant motion mechanism (200), C. The second rotary joint (300) is adapted to be connected to a human arm (6), the second rotary joint (300) defines a second joint rotation axis Y, the second rotary joint (300) is adapted to be arranged according to the degree of flexion and extension of a human shoulder joint, the second rotary joint (300) is connected to the super-redundant motion mechanism (200) at a second end of the super-redundant motion mechanism (200); wherein the underactuated mechanism (1) is configured to transfer a reverse torque and a reaction force from the second rotary joint (300) to the first rotary joint (100), in: - The first joint rotation axis X is coplanar with the second joint rotation axis Y; - the first rotary joint (100) is not driven; - the second rotary joint (300) is driven in the following manner: remotely via a driven pulley and Bowden cable, or via a direct drive drive system with a co-located motor; -The super redundant motion mechanism (200) comprises at least three components (210, 220, 231) connected together by a rotation joint whose axes are parallel to each other (A, B, F), allowing the shoulder joint to move in different directions, wherein one component (210) of the at least three components is fixed to a first rotation joint (100) and another component (220) of the at least three components is fixed to a second rotation joint (300).

16. A robotic shoulder exoskeleton comprising an underactuated mechanism (1) according to at least one of the preceding claims.

17. The shoulder exoskeleton according to claim 16 comprises a first trunk connection device (3), connected to the first rotational joint (100) and configured to fix the under-actuated mechanism (1) to the human trunk (5), and a relative second arm connection device (4) connected to the second rotational joint (300) and configured to fasten the under-actuated mechanism (1) to the human arm (6), so as to realize remote actuation and torque transmission of the shoulder joint.

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