Kinematics for the compensation of a variable load and exoskeleton that uses such kinematics

Abstract

A kinematic system (100) for compensating a variable load, said kinematic system (100) comprising a first link (110) arranged, in use, to be integrally constrained to a frame (10); a second link (120) rotatably connected to the first link (110) by means of a first rotational joint (115); a third link (130) rotatably connected to the second link (120) by means of a second rotational joint (125); a fourth link (140) rotatably connected to the third link (130) by means of a third rotational joint (135), said fourth link (140) being further rotatably connected to the first link (110) by means of a fourth rotational joint (145). The kinematic system (100) also comprises a first elastic element (150) having a first end (151), rotatably connected to the frame (10) by means of a fifth rotational joint (155), and a second end (152), rotatably connected to a first fastening link by means of a sixth rotational joint (156); a second elastic element (160) having a first end (161), rotatably connected to a second fastening link by means of a seventh rotational joint (165), and a second end (162), rotatably connected to a third fastening link, not adjacent to the second fastening link, by means of a eight rotational joint (166). In particular, the first fastening link is selected between the second link (120) and the fourth link (140), the second fastening link is selected between the first link (110) and the second link (120), the third fastening link is selected between the third link (130) and the fourth link (140).

Description

TITLEKinematics for the compensation of a variable load and exoskeleton that uses such kinematicsDESCRIPTIONField of the invention

[0001] The present invention relates to a kinematic system for compensating a load of variable entity with the movement of the kinematic system.

[0002] Furthermore, the invention relates to an exoskeleton for assisting in the elevation of a joint comprising such kinematic system.Description of the prior art

[0003] The shoulder joint is one of the most complex anatomical joints in the human body, with five degrees of freedom that allow for a wide range of motion in all directions. This means that the shoulder can rotate on itself like a ball and socket joint, but it can also move up and down, and move forward and back relative to the torso.

[0004] This freedom of movement makes the shoulder a very versatile joint and essential for everyday activities. However, the biomechanical complexity of the joint also makes the shoulder particularly vulnerable to injury, damage, and degenerative diseases.

[0005] An exoskeleton that assists with shoulder flexion has significant advantages for workers with strenuous tasks as well as for patients with neurological or musculoskeletal conditions. In particular, this device can be used both in the clinical setting in the rehabilitation of plexus-injured patients to restore shoulder functionality and improve their quality of life, and in the industrial setting to reduce physical fatigue and injury risks for workers by mitigating the consequences of wearing movements on the shoulder joint.

[0006] One of the main problems associated with the use of these exoskeletons is human-machine interaction, which must take into account the anatomical and functional characteristics of the shoulder, which have a large variety of movements and a large range of amplitude in the movements themselves. Furthermore, human-machine interaction requires that the device provides assistance only when necessary and in such a way as not to interfere with the user's freedom of movement.

[0007] To address these problems, many of these devices use a variety of mechanisms to improve shoulder alignment and support. For example, passive joints (therefore not actuated but free to move) can be used to allow the exoskeleton to autonomously adapt to human movements. Additionally, motors or actuators can be used to assist shoulder flexion according to planned strategies.

[0008] However, these devices can cause so-called "parasitic" loads on the wearer's shoulder, which can be uncomfortable or even harmful. The primary place of stress on the shoulder may be the weight of the device itself, compromising fatigue reduction for workers and rehabilitation for trauma patients.

[0009] Therefore, it is important that the device design includes a weight compensation mechanism that reduces the load on the shoulder. This can be achieved, for example, by distributing the weight of the device to other parts of the body, such as the lower back or hips, to reduce the load on the shoulder and upper torso and increase comfort.

[0010] Among the parasitic loads, it is also essential to consider the constraint reaction due to shoulder flexion. The exoskeleton provides the torque needed to assist shoulder elevation, and this torque necessarily corresponds to a reaction on the proximal joints of the robot that weigh on the interface that connects the exoskeleton to the wearer. Therefore, the exoskeleton must be able to support this reaction together with the weight of the arm and the distal components of the exoskeleton itself.Summary of the invention

[0011] It is then a feature of the present invention to provide a kinematic system for compensating a variable load that allows to produce an elastic moment variable as afunction of the moment generated by the load itself during the movement of the kinematic system.

[0012] It is also a feature of the present invention to provide an exoskeleton for assisting in the elevation of a shoulder joint comprising such kinematic system.

[0013] These and other objects are achieved by a kinematic system for compensating a variable load, said kinematic system comprising:- a first link arranged, in use, to be integrally constrained to a frame;- a second link rotatably connected to said first link by means of a first rotational joint having a rotation axisorthogonal to a plane 11 and intersecting said plane 11 in a center of rotation oi;- a third link rotatably connected to said second link by means of a second rotational joint having a rotation axis z2orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation o2;- a fourth link rotatably connected to said third link by means of a third rotational joint having a rotation axis z3orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation 03, said fourth link being further rotatablyconnected to said first link by means of a fourth rotational joint having a rotation axis z4orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation 04;- a first elastic element having a first end, rotatably connected to said frame by means of a fifth rotational joint having a rotation axis z5orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation Alfand a second end, rotatably connected to a first fastening link by means of a sixth rotational joint having a rotation axis z6orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation Blfsaid first elastic element arranged to generate a first elastic forcehaving direction parallel to the segment A1B1;- a second elastic element having a first end, rotatably connected to a second fastening link by means of a seventh rotational joint having a rotation axis z7orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation J42, and a second end, rotatably connected to a third fastening link, not adjacent to said second fastening link, by means of a eight rotational joint having a rotation axis z8orthogonal to said plane11 and intersecting said plane 11 in a center of rotation B2, said second elastic element arranged to generate a second elastic force Fet2having direction parallel to the segment A2B2; said first fastening link being selected between said second link and said fourth link, said second fastening link being selected between said first link and said second link, said third fastening link being selected between said third link and said fourth link, wherein:- the angle 0 is defined as the angle between segment0403and the direction normal to the segment O4O1,- the distance e is defined as the distance, alternatively:— between the segment A1B1and said center of rotation 04if said first fastening link is said second link;— between the segment A1B1and said center of rotation 04if said first fastening link is said fourth link; with emtn < e < emax;- the angle fl is defined as the angle, alternatively:— between the segment A2B2and the segment O2O2,if said second fastening link is said second link;— between the segment A2B2and the segment 0402, if said second fastening link is said first link;where 6max, emin, emax, fiminand / 3maxare predetermined values, whose main feature is that said kinematic system is configured to pass between:- a first configuration, in which 0 = 0, e= eminand P ~ Pmax'- a second configuration, in which 0 = 0max, e = emaxand P = pmin.

[0014] As a consequence of the geometric constraints described above, the following relations are valid:Mel= Metl+ Met2where Meilis the elastic torque generated by the first elastic element, Mei2is the elastic torque generated by the second elastic element and Metis the overall elastic torque generated by the elastic elements.

[0015] Therefore, when the kinematic system is in the first configuration, the first elastic force Fei4generates a minimum elastic torque Meil, whereas the second elastic force Fe(2generates a maximum elastic torque Mei2. Vice-versa, whenthe kinematic system is in the second configuration, the first elastic force Fei4generates a maximum elastic torque Metl, whereas the second elastic force Fet2generates a minimum elastic torque Mei2.

[0016] In this way, it is possible to appropriately size the values of the elastic constants of the elastic elements so that, by applying to the third link an external force that varies as the angle 0 varies, the overall elastic torque Metvaries in such a way as to appropriately balance this external force.

[0017] In particular, it is possible to obtain an overall elastic torque Metthat increases in an increasing or decreasing manner as a function of the value of the angle e.

[0018] Advantageously:- the segment O4O1 has a length equal to l4;- the segment O1O2 has a length equal to l2;- the segment O2O3has a length equal to Z3, where 0.9*^1 < ^3 < 1-1 *G '- the segment 0304has a length equal to Z4, where 0.9* Z2< Z4< 1.1*l2.

[0019] In particular, l3= l4and Z4= l2.

[0020] This way, the four links of the kinematic system are an articulated parallelogram.

[0021] In particular, there is 0 < emin< 0.04*l4.

[0022] More in particular, there is emin= 0.

[0023] In particular, there is 0 < / 3mtn< 2°.

[0024] More in particular, there is (3mtn~ 0.

[0025] Advantageously, a first auxiliary elastic element is also provided having a first end, rotatably connected to said frame by means of a ninth rotational joint having a rotation axis z9orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation Al'fand a second end, rotatably connected to a first auxiliary fastening link by means of a tenth rotational joint having a rotation axis z10orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation B[, said first auxiliary elastic element arranged to generate a first auxiliary elastic force Fgtlhaving direction parallel to the segment A^B^, said first auxiliary fastening link being said fourth link if said first fastening link is said second link and vice-versa, the distance e' being defined as the distance, alternatively :- between the segment A4B4and said center of rotationif said first auxiliary fastening link is said second link;- between the segment A4B4and said center of rotation 04if said first auxiliary fastening link is said fourth link; with emtn A e < emax.

[0026] Advantageously, said first elastic element is a traction or compression spring.

[0027] Advantageously, said second elastic element is a traction or compression spring.

[0028] According to another aspect of the invention, a exoskeletal system is claimed arranged to be made integral with a user, said exoskeletal system comprising the kinematic system according to any of claims from 1 to 7.

[0029] In particular, said exoskeletal system is configured in such a way that said frame to which said first link of said kinematic system is connected is arranged to be connected to the back of a user.

[0030] In particular, said exoskeletal system also comprises a kinematic system for assisting the flexionextension of the shoulder to which the kinematic system according to the present invention is connected by means of passive or active rotary joints.

[0031] Advantageously, the kinematic system for assisting the flexion-extension of the shoulder is disclosed in IT102024000013081 .

[0032] In particular, the kinematic system for assisting the flexion-extension of the shoulder comprises:- a first link arranged, in use, to be integrally constrained to said mass;- a second link arranged, in use, to be integrallyconstrained to a frame, said second link being rotatably connected to said first link by means of a first rotational joint having a first rotation axis z4orthogonal to a plane 11 and intersecting said plane 11 in a first center of rotation 0lfsaid mass generating a couple gravitational Mgwith respect to said first rotation axis z4;- a third link rotatably connected to said second link by means of a second rotational joint having a second rotation axis z2orthogonal to said plane 11 and intersecting said plane 11 in a second center of rotation 02;- a fourth link rotatably connected to said third link by means of a third rotational joint having a third rotation axis z3orthogonal to said plane 11 and intersecting said plane 11 in a third center of rotation 03, said fourth link being further rotatably connected to said first link by means of a fourth rotational joint having a fourth rotation axis z4orthogonal to said plane 11 and intersecting said plane 11 in a fourth center of rotation 04; wherein:- the segment O4O2has a length equal to Z2;- the segment O2O3has a length equal to l3>l2;- the segment 0304has a length equal to l4>l2;- the segment O4O1 has a length equal to l4>l2;- the segment O4O1 forms with the segment O1O2 an angle equal to T94, arranged to vary with said relative rotation between said first link and said second link;- the segment O1O2 forms with the segment O2O3an angle equal to I92, arranged to vary with said relative rotation between said second link and said third link;- the segment O2O3forms with the segment 0304an angle equal to T93, arranged to vary with said relative rotation between said third link and said fourth link;- the segment 0304forms with the segment O4O1 an angle equal to $4, arranged to vary with said relative rotation between said first link and said fourth link; whose main feature is that said kinematic system is configured in such a way that:- if l4> l3and l4> l4then l4+ l2< l3+ l4;- if l3> l4and l3> l4then l3+ l2< l4+ l4;- if l4> l4and l4> l3then l4+ l2< l4+ l3; and that at least one elastic group is provided arranged to generate an elastic torque Meiwith respect to said first rotation axis x4opposite in direction to said gravitationaltorque Mg.Brief description of the drawings

[0033] The invention will be now shown with the following description of some embodiments, exemplifying but not limitative, with reference to the attached drawings in which:- Fig. 1A schematically shows a possible embodiment of the kinematic system according to the present invention, in the first configuration, in which the first elastic element is connected to the second link and the second elastic element is connected to the second and fourth links;- Fig. IB schematically shows an embodiment of Fig. 1A in the second configuration;- Fig. 2A schematically shows a variant of the embodiment of Fig. 1A in which the first elastic element is connected to the fourth link;- Fig. 2B schematically shows a variant of the embodiment of Fig. 1A, in which the first elastic element is connected to the second link and the first auxiliary elastic element is connected to the fourth link;- Fig. 3A schematically shows a variant of the embodiment of Fig. 1A in which the second elastic element is connected to the first and third links;- Fig. 3B schematically shows a variant of the embodiment of Fig. 3A in which the first elastic element is connected to the fourth link;- Fig. 4 shows a possible applicative embodiment of the kinematic system of Fig. 2B;- Fig. 5A schematically shows a possible embodiment of the exoskeleton for the flexion / extension of the shoulder of a user comprising the kinematic system according to the present invention connected, by means of some passive rotational constraints, to a kinematic system of flexion / extension of the shoulder;Fig. 5B shows a possible applicative embodiment of the exoskeleton shown in Fig. 5A.Description of some preferred embodiments

[0034] With reference to Figs. 1A and IB, in a possible embodiment according to the present invention, the kinematic system 100 comprises a first link 110 integral to a frame 10, a second link 120 rotatably connected to the first link by means of a rotational joint 115, a third link rotatably connected to the second link 120 by means of a rotational joint 125 and a fourth link rotatably connected to the third link by means of a rotational joint 135 and to the first link 110 by means of a rotational joint 145.

[0035] In particular, defining the plane 11 as the plane of the sheet, the rotational joints 115, 125, 135 and 145 have rotation axes that intersect the plane 11, respectively, in the centers of rotation O1, O2, O3and 04.

[0036] The axis x and the axis y are also defined as perpendicular axes lying on the plane 11. In particular, the axis y is defined as the axis parallel to the segment 0401.

[0037] In particular, the segment O1O2 has a length equal to l2, the segment O2O3has a length equal to l3, the segment O3O4 has a length equal to Z4= l2and the segment 0401has a length equal to l4= l3, in such a way that the links 110, 120, 130 and 140 form an articulated parallelogram, where the second link 120 and the fourth link 140 can rotate with respect to the first link 110, forming the same angle 0 with respect to the axis x.

[0038] The kinematic system also comprises a first elastic element 150, in particular a traction or compression spring, having a first end 151 rotatably connected to the frame 10 by means of a rotational joint 155 and a second end 152 rotatably connected to the second link 120 by means of a rotational joint 156. In particular, the rotational joints 155 and 156 have rotation axes that intersect the plane 11, respectively, in the centers of rotation A4and B4.

[0039] As shown in Fig. 1A, when the angle 0 = 0, the center of rotation A4and the center of rotation O4are located ata distance alxalong the axis x and at a distance alyalong the axis y and, similarly, the center of rotationand the center of rotation 0±are located at a distance blxalong the axis x and at a distance blyalong the axis y. Furthermore, the segment A1B1forms an angle (p with the axis y, where (p < 90°.

[0040] The kinematic system then comprises a second elastic element 160, in particular a traction or compression spring, having a first end 161 rotatably connected to the second link 120 by means of a rotational joint 165 and a second end 162 rotatably connected to the fourth link 140 by means of a rotational joint 166. In particular, the rotational joints 165 and 166 have rotation axes that intersect the plane 11, respectively, in the centers of rotation J42and B2-

[0041] As shown in Fig. 1A, when the angle 0 = 0, the center of rotation J42and the center of rotation O2are located at a distance a2xalong the axis x and at a distance a2yalong the axis y and, similarly, the center of rotation B2and the center of rotation O2are located at a distance b2xalong the axis x and at a distance b2yalong the axis y.

[0042] With reference to Fig. 1A, the angle fl is also defined as the angle between the segment A2B2and the segment O2O2, where ftmin< (3< ftmaxr whereas, with reference to Fig.IB, the distance e is defined as the distance between thesegment A1B1and the center of rotation 0lrwhere emin< e <^max•

[0043] In particular, emtnand ftmtnare the minimum values, respectively, that e and ft can assume when 0 varies, whereasemax and ftmaxarethe maximum values, respectively, that e and ft can assume when 0 varies.

[0044] In particular, the kinematic system 100 is configured to switch between a first configuration, as shown in Fig. 1A, wherein 0 = 0, e = eminand ft = (3maXr and a second configuration, as shown in Fig. IB, wherein 0 = 0max, e= emaxand P = pmin.

[0045] From the geometric definitions expressed and shown in Figs. 1A and IB, the following relationships can be verified:Mel= Metl+ Met2where Meilis the elastic torque generated by the first elastic element, Mei2is the elastic torque generated by the second elastic element and Metis the overall elastic torque generated by the elastic elements.

[0046] Therefore, when the kinematic system 100 is in the first configuration, the first elastic forcegenerates a minimum elastic torque Meilfwhereas the second elastic force Fei2generates a maximum elastic torque Mei2. Vice-versa, when the kinematic system 100 is in the second configuration, the first elastic forcegenerates a maximum elastic torque Meil, whereas the second elastic force Pei2 generates a minimum elastic torque Mei2.

[0047] In this way, it is possible to appropriately size the values of the elastic constants of the elastic elements so that, by applying to the third link 130 an external force that varies as the angle 0 varies, the overall elastic torque Metvaries in such a way as to appropriately balance this external force.

[0048] In particular, it is possible to obtain an overall elastic torque Metthat increases in an increasing or decreasing manner as a function of the value of the angle e.

[0049] In particular, by appropriately sizing the values of alx, aly, blx, bly, a2x, a2y, b2xand b2yit is possible to obtain the values emin= 0 and Pmin— 0.

[0050] In particular, to obtain emjn= 0 the kinematic system 100 has to be sized in such a way that the equation bXy / bXx= aly / alxis valid.

[0051] In particular, to obtain (3min= 0 the kinematic system 100 has to be sized in such a way that the equationis valid.

[0052] This way, in the first configuration the overall elastic torque Meiis mainly provided by the spring 150whereas in the second configuration the overall elastic torque Meiis mainly provided by the spring 160. Such solution allows to have an overall elastic torque Metlinearly increasing or decreasing as the angle 0 varies and included between two end values easily definable by means of the elastic constants of the two springs 150 and 160, so as to optimally compensate the external force.

[0053] Furthermore, by decoupling the contents of the springs 150 and 160, it is possible to size the spring 150 and the links 120 and 140 independently from the size of the spring 160 and the links 110 and 130, providing greater operational flexibility in the construction phase of the kinematic system in the choice of geometry and appropriate components .

[0054] In Figs. 2A, 2B, 3A and 3B, some variants provided for by the kinematic system 100, according to the present invention, are shown in an exemplary and non-limiting manner.

[0055] In particular, in the embodiment of Fig. 2A, the spring 150 is constrained to the fourth link 10 instead of the second link 120. In this case, the distance e has to be defined as the distance between the segment A1B1and the center of rotation O2. The considerations made for Fig. 1A regarding the elastic torque Meilremain completelyanalogous, as well as the technical effects of the kinematic system 100.

[0056] Fig. 2B shows an embodiment in which there is both an elastic element 150 and an auxiliary elastic element 150', constrained, respectively, to the second and fourth link. In this case, it is necessary to consider two elastic torques Meiland Me'tldepending on respective values e and e', defined as distances of the segments A1B1andfrom the centers of rotation O4and 04. Such elastic torques Metland Me'tlare added together allowing the elastic torque provided in the first configuration to be divided between the two springs 150 and 150'.

[0057] Figs. 3A and 3B show instead two embodiments in which the second spring 160 is constrained to the first link 110 and to the third link 130, instead of the second link 120 and the fourth link 140. The kinematic system works in a completely analogous manner to that described previously.

[0058] Fig. 4 shows a possible exoskeletal embodiment of the embodiment of the kinematic system 100 shown in Fig. 2B. For clarity, Fig. 4 shows the segments and the centers of rotation described above.

[0059] Furthermore, in Fig. 4 the kinematic system comprises two screws 154 and 164 arranged to vary the preload, respectively, of the springs 150 and 160.

[0060] With reference to Figs. 5A and 5B, the kinematic system 100 shown in Fig. 4, or an embodiment shown previously, can be used within an exoskeletal system 300 for the flexion-extension assistance of a shoulder of a user.

[0061] In particular, in the exoskeletal system 300, the kinematic system 100 can be constrained, by means of a rotational joint to the back of a user and, by means of other passive joints, to a shoulder flexion-extension assistance kinematic system 200. In this case, the external force acting on the third link 130 is produced by the constraint reactions discharged by the flexion-extension assistance kinematic system 200 and are appropriately compensated by the kinematic system 100, as described above.

[0062] In particular, the shoulder flexion-extension assistance kinematics 200 is described in IT102024000013081 and PCT / IB2025 / 055851.

[0063] The foregoing description embodiments of the invention will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and / or adapt for various applications such embodiment without further research and without parting from the invention, and, accordingly, it is therefore to be understood that such adaptations and modifications will have to be considered asequivalent to the specific embodiments. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.

Claims

CLAIMS1. A kinematic system (100) for compensating a variable load, said kinematic system (100) comprising: a first link (110) arranged, in use, to be integrally constrained to a frame (10); a second link (120) rotatably connected to said first link (110) by means of a first rotational joint (115) having a rotation axisorthogonal to a plane 11 and intersecting said plane 11 in a center of rotation Ox; a third link (130) rotatably connected to said second link (120) by means of a second rotational joint (125) having a rotation axis z2orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation O2,' a fourth link (140) rotatably connected to said third link (130) by means of a third rotational joint (135) having a rotation axis z3orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation O3, said fourth link (140) being further rotatably connected to said first link (110) by means of a fourth rotational joint (145) having a rotation axis z4orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation o4;a first elastic element (150) having a first end (151), rotatably connected to said frame (10) by means of a fifth rotational joint (155) having a rotation axis z5orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation Alfand a second end (152), rotatably connected to a first fastening link by means of a sixth rotational joint (156) having a rotation axis z6orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation Blfsaid first elastic element (150) arranged to generate a first elastic force Fg^ having direction parallel to the segment A1B1; a second elastic element (160) having a first end (161), rotatably connected to a second fastening link by means of a seventh rotational joint (165) having a rotation axis z7orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation J42, and a second end (162), rotatably connected to a third fastening link, not adjacent to said second fastening link, by means of a eight rotational joint (166) having a rotation axis zsorthogonal to said plane 11 and intersecting said plane 11 in a center of rotation B2, said second elastic element (160) arranged to generate a secondelastic force Fei2having direction parallel to the segment A2B2; said first fastening link being selected between said second link (120) and said fourth link (140), said second fastening link being selected between said first link (110) and said second link (120), said third fastening link being selected between said third link (130) and said fourth link (140), wherein: the angle 0 is defined as the angle between segment O4O3and the direction normal to the segment O4O1,the distance e is defined as the distance, alternatively:— between the segment A1B1and said center of rotation O4if said first fastening link is said second link (120);— between the segment A1B1and said center of rotation 04if said first fastening link is said fourth link (140); with emtn < e < emax; the angle fl is defined as the angle, alternatively:— between the segment A2B2and the segment O2O2, if said second fastening link is said second link(120);— between the segment A2B2and the segment O4O3, if said second fastening link is said first link (110);where 6max, emin, emax, fiminand / 3maxare predetermined values, said kinematic system (100) characterized in that it is configured to pass between: a first configuration, in which 0 = 0, e= eminand P ~ Pmax' a second configuration, in which 0 = 0max, e = emaxand P = pmin.

2. The kinematic system (100), according to claim 1, wherein: the segment O4O1 has a length equal to Zx; the segment O1O2 has a length equal to l2; the segment O2O3has a length equal to Z3, where 0.9*^1 < ^3 < 1-1 *G ' the segment 0304has a length equal to l4, where 0.9*Z2< Z4< 1-1*Z2•3. The kinematic system (100), according to claim 2, wherein 0 < emin< 0.04*l4.

4. The kinematic system (100), according to claim 1, wherein 0< / ?min<2°.

5. The kinematic system (100), according to claim 1, wherein a first auxiliary elastic element (150’) is also provided having a first end (151'), rotatably connected to said frame (10) by means of a ninth rotational joint (155') having a rotation axis z9orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation A'lfand a second end (152'), rotatably connected to a first auxiliary fastening link by means of a tenth rotational joint (156’) having a rotation axis z10orthogonal to said plane 11 and intersecting said plane 11 in a center of rotation B[, said first auxiliary elastic element (150’) arranged to generate a first auxiliary elastic forcehaving direction parallel to the segment A^B^, said first auxiliary fastening link being said fourth link (140) if said first fastening link is said second link (120) and vice-versa, and wherein the distance e' is defined as the distance, alternatively: between the segment A4B4and said center of rotationif said first auxiliary fastening link is said second link (120); between the segment A4B4and said center of rotation 04if said first auxiliary fastening link is said fourth link (140);with emin< e < emax.

6. The kinematic system (100), according to claim 1, wherein said first elastic element (150) is a traction or compression spring.

7. The kinematic system (100), according to claim 1, wherein said second elastic element (160) is a traction or compression spring.

8. An exoskeletal system (300) arranged to be made integral with a user, said exoskeletal system (300) comprising the kinematic system (100) according to any of claims from 1 to 7.

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