Kinematics for the compensation of an extremity load and exoskeleton that uses such kinematics

Abstract

A kinematic system (100) for compensating the weight of a mass (10), said kinematic system (100) comprising a first link (110) arranged, in use, to be integrally constrained to the mass (10); a second link (120) arranged, in use, to be integrally constrained to a frame (20),, and being rotatably connected to the first link (110) by means of a first rotational joint (115) having a rotation axis Z1 orthogonal to a plane Π and intersecting the plane Π in a first center of rotation O 1 the mass generating a gravitational torque Mg with respect to the first rotation axis Z1; a third link (130) rotatably connected to the second link (120) by means of a second rotational joint (125) having a second rotation axis Z2 orthogonal to the plane Π and intersecting the plane Π in a second center of rotation O 2; a fourth link (140) rotatably connected to the third link (130) by means of a third rotational joint (135) having a third rotation axis Z3 orthogonal to the plane Π and intersecting the plane Π in a third center of rotation 0 3, the fourth link (140) being also rotatably connected to the first link (110) by means of a fourth rotational joint (145) having a fourth rotation axis Z4 orthogonal to the plane Π and intersecting the plane Π in a fourth center of rotation O 4. In particular, the segment (I) has length equal to l 2, the segment (II) has length equal to l 3 ≥ l 2 , the segment (III) has length equal to l 4 ≥ l 2 and the segment (IV) has length equal to l 4 ≥ l 2. Furthermore, the segment (V) forms with the segment (VI) an angle equal to v 1, the segment (VII) forms with the segment (VIII) an angle equal to v 2, the segment (IX) forms with the segment (X) an angle equal to v 3 and the segment (XI) forms with the segment (XII) an angle equal to v 4. In particular, the kinematic system (100) is configured in such a way that if l 1 ≥ l 3 and l 1 ≥ l 4 then l 1 + l 2 ≤ l 3 + l 4, if l 3 ≤ l 1 and l 3 ≥ l 4 then l 3 + l 2 ≤ l 1 + l 4 and if l 4 ≥ l 1 and l 4 ≥ l 3 then l 4 + l 2 ≤l 1 + l 3. Furthermore, at least one elastic group (116, 126, 136, 146) is provided arranged generate an elastic torque M el with respect to the first rotation axis %1 opposite in direction to the gravitational torque Mg.

Description

TITLEKinematics for the compensation of an extremity load and exoskeleton that uses such kinematicsDESCRIPTIONField of the invention

[0001] The present invention relates to a kinematics for the compensation of a weight during the movement of the kinematics itself.

[0002] Furthermore, the invention relates to an exoskeleton for the assistance in the flexion-extension of a joint comprising such kinematics.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 movement in all directions. This means that the shoulder can rotate on itself like a ball and socket joint, but 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 and essential joint for everyday activities. However, the complexity of the joint also makes the shoulder particularly vulnerable to injuries, lesions and degenerative diseases.

[0005] An exoskeleton that assists shoulder flexion has significant advantages for workers forced to perform strenuous tasks but also for patients suffering from neurological or musculoskeletal diseases. In particular, such a device can be used in the rehabilitation of plexus- injured patients to restore shoulder function and improve their quality of life.

[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 a way that does not 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 (i.e. non-actuated but free to move) can be used to allow the exoskeleton to autonomously adapt to human movements. Furthermore, motors or actuators can be used to provide assistance to shoulder flexion according to planned strategies.

[0008] However, these devices can cause so-called "parasitic" loads on the wearer's shoulder, which can beannoying or even harmful. The first place to put pressure on the shoulder could 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 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 necessary 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 distal components of the exoskeleton itself.Summary of the invention

[0011] It is therefore a feature of the present invention to provide a kinematic system of compensating the weight of a mass that allows the production of an elastic moment that varies as a function of the torque generated by the mass itself during the movement of the kinematics.

[0012] It is also a feature of the present invention to provide an exoskeleton for assisting the flexion / extension of a joint comprising such kinematics.

[0013] These and other objects are achieved by a kinematic system for compensating the weight of a mass, said kinematic system comprising:- a first link arranged, in use, to be integrally constrained to said mass;- a second link arranged, in use, to be integrally constrained 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 Zi orthogonal to a plane 11 and intersecting said plane 11 in a first center of rotation 0lfsaid mass generating a gravitational torque Mgwith respect to said first rotation axis zx;- 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 ofrotation 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 0^ 2 has length equal to l2;- the segment O2O3has length equal to l3> l2;- the segment 0304has length equal to l4>l2;- the segment 0404has length equal to l4>l2;- the segment 0404forms 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 $2, 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 0404an angle equal to $4, arranged to vary with said relative rotation between said first link and said fourthlink; whose main feature is that said kinematic system is configured in such a way that:- if Zi≥l3and l4> l4then l4+ l2< l3+ Z4;- 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 generate an elastic torque Metwith respect to said first rotation axis x4opposite in direction to said gravitational torque Mg.

[0014] This way, the present invention allows to compensate for the weight of the mass, obtaining a direct proportionality between Metand Mgas T94varies.

[0015] Advantageously, a main elastic group is provided arranged to generate an internal torque M4between said first link and said fourth link.

[0016] In particular, an auxiliary elastic group is provided arranged to generate an internal torque M4between said first link and said second link.

[0017] In particular, an auxiliary elastic group is provided arranged to generate an internal torque M2between said second link and said third link.

[0018] In particular, an auxiliary elastic group is provided arranged to generate an internal torque M3between said third link and said fourth link.

[0019] Advantageously, at least one elastic group comprises a torsional spring.

[0020] In particular, at least one elastic group comprises the torsional spring described in W02020 / 104962.

[0021] Alternatively, at least one elastic group comprises a linear spring.

[0022] In particular, the linear spring is a gas spring.

[0023] Advantageously, a fifth elastic group is provided comprising a linear spring arranged to connect said second link and said fourth link.

[0024] In particular, at least one elastic group comprises a preload device arranged to vary the deformation length of said elastic group.

[0025] In particular, said preload device comprises a kinematic constraint arranged to move the connection point between an end of said linear spring and a related link.

[0026] In particular, the preload device may comprise a cam or worm screw mechanism.

[0027] In particular, said first link is constrained to said mass in such a way that said segment O4O1 forms an angle am< 40° with the segment 040m, where Omis the gravitational center of said mass.

[0028] In particular, at least one elastic group comprises two springs arranged in parallel.

[0029] In particular, at least one elastic group comprises two springs arranged in series.

[0030] Advantageously, there is 2,9 < Z3 / Z2< 8,6, 2,9 < Z4 / Z2< 6,1, 2,9 < Zi / Z2< 5,7.

[0031] In particular, there is l±= Z3= Z4= 5*Z2and said first elastic group has an elastic constant K equal to:K = - 36■Mg / [4■TI- 18■atan(V5 / 5)]

[0032] According to another aspect of the invention, an exoskeletal system is claimed that can be made integral with a user, said exoskeletal system comprising the kinematics according to one of claims 1 to 9.

[0033] In particular, said exoskeletal system is applied to the torso of said user and said kinematics is capable of supporting the flexion-extension of an upper limb, such as for example the shoulder, the elbow, the wrist or a finger.

[0034] In particular, said exoskeletal system is applied to the torso of said user and said kinematics is designed to support the flexion-extension of a lower limb, such as the hip, knee or ankle.Brief description of the drawings

[0035] The invention will be now shown with the following description of its exemplary embodiments, exemplifying but not limitative, with reference to the attached drawings in which:- Fig. 1 schematically shows an embodiment of the kinematic system for compensating the weight of a mass, according to the present invention, where a first elastic group is present comprising a torsional spring;- Figs. 2A and 2B show the following steps of the flexion / extension of the shoulder of a user to which the kinematic system according to the present invention is applied;- Fig. 3 shows an embodiment of the kinematic system for compensating the weight of a mass, according to the present invention, wherein a first and a second elastic group are provided, both comprising a torsional spring;- Fig. 4 shows an embodiment of the kinematic system for compensating the weight of a mass, according to the present invention, where a first elastic group is present comprising two torsional springs in parallel ;- Fig. 5 shows a plan view of an exoskeleton for assisting the flexion / extension of a joint of a user, according to the present invention, comprising the kinematic system for compensating the weight of a mass;Fig. 6 shows in perspective the exoskeleton of Fig.5.Description of some preferred exemplary embodiments

[0036] With reference to Figs. 1 to 4, the kinematic system 100 for compensating the weight of a mass 10, according to the present invention, comprises a first link 110, 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 and a fourth link 140 rotatably connected to the third link 130 by means of a third rotational joint 135 and rotatably connected to the first link 110 by means of a fourth rotational joint 145.

[0037] In particular, the first link 110 is arranged, in use, to be integrally constrained to the mass 10, whereas the second link 120 is arranged, in use, to be integrally constrained to a frame 20. In particular, the mass 10 is schematized by means of its center gravitational Omand the weight force F that it produces. In the application example of Figs. 2A and 2B, the frame 20 corresponds to the back of the user, or to an exoskeleton integral with the back, whereas the mass 10 comprises both the user's arm and the exoskeleton itself.

[0038] As shown in the figures, the first rotational joint 115 is arranged to allow a relative rotation between the first link 110 and the second link 120 about a first rotationaxis z4orthogonal to a plane 11, parallel to the plane of the sheet; the first rotation axis z4intersects the plane 11 in a first center of rotation 04. Furthermore, the mass 10 generates a gravitational torque Mgwith respect to this first rotation axis z4.

[0039] Similarly, the second rotational joint 125 is arranged to allow a relative rotation between the second link 120 and the third link 130 about a second rotation axis z2orthogonal to the plane 11; the second rotation axis z2intersects the plane 11 in a second center of rotation O2.

[0040] Similarly, the third rotational joint 135 is arranged to allow a relative rotation between the third link 130 and the fourth link 140 about a third rotation axis z3orthogonal to the plane 11; the third rotation axis z3intersects the plane 11 in a third center of rotation O3.

[0041] Similarly, the fourth rotational joint 145 is arranged to allow a relative rotation between the first link 110 and the fourth link 140 about a fourth rotation axis z4orthogonal to the plane 11; the fourth rotation axis z4intersects the plane 11 in a fourth center of rotation 04.

[0042] Furthermore, for the sake of clearness, the following relations are defined: the segment O4O2has length equal to Z2; the segment O2O3has length equal to l3> l2; the segment O3O4has length equal to l4>l2;the segment 0404has length equal to Z4>Z2; the segment 0401forms with the segment O4O2an angle equal to T94, arranged to vary with the relative rotation between the first link 110 and the second link 120; the segment O4O2forms with the segment O2O3an angle equal to $2, arranged to vary with the relative rotation between the second link 120 and the third link 130; the segment O2O3forms with the segment O3O4an angle equal to $3, arranged to vary with the relative rotation between the third link 130 and the fourth link 140; the segment O3O4forms with the segment 0404an angle equal to $4, arranged to vary with the relative rotation between the first link 110 and the fourth link 140.

[0043] In particular, the kinematic system 100 is configured in such a way that: if Z4≥Z3and l4> Z4then Z4+ Z2≤ Z3+ Z4; if Z3≥Z4and Z3≥Z4then Z3+ Z2≤ l4+ Z4; if Z4≥Z4and Z4≥Z3then Z4+ Z2≤ Z4+ Z3.

[0044] This way, the kinematic system 100 is mechanically compatible to achieve a complete rotation = 360° around the first rotation axis z4.

[0045] Furthermore, the kinematic system 100 comprises at least one elastic group arranged to generate an elastic torque Metwith respect to the first rotation axisopposite in direction to the gravitational torque M^.

[0046] In particular, in the embodiment of Fig. 1 the kinematic system 100 comprises a main elastic group 146 comprising a torsional spring arranged to generate an internal torque M4between the first link 110 and the fourth link 140.

[0047] In the embodiment of Fig. 3, instead, the kinematic system 100 comprises, in addition to the main elastic group 146, also an auxiliary elastic group 136 arranged to generate an internal torque M3between the third link 130 and the fourth link 140.

[0048] In the embodiment of Fig. 4, finally, the kinematic system 100 comprises both the main elastic group 146 and the auxiliary elastic group 136, and the main elastic group 146 comprises two torsional springs 146',146'’ in parallel to each other.

[0049] The embodiments shown for illustrative purposes in Figs. 1, 3 and 4 are only some examples of the possible combinations of elastic groups that the present invention intends to protect.

[0050] In particular, there may also be present, either alternatively or in combination, also an auxiliary elasticgroup 116 arranged to generate an internal torquebetween the first link 110 and the second link 120 and an auxiliary elastic group 126 arranged to generate an internal torque M2between the second link 120 and the third link 130.

[0051] Furthermore, each elastic group 116,126,136,146 can comprise one or several elastic elements, such as torsional or linear springs or other types of elastic elements capable of generating an internal elastic torque between the links to which they are connected.

[0052] For example, linear springs can also be provided to connect the first link 110 and the third link 130 or the second link 120 and the fourth link 140.

[0053] In particular, the following relationship is considered valid:wherein:Mi is the internal torque generated between the links adjacent to the respective center of rotationOn rri is the reduction ratio by which this internal torque Mi must be multiplied to calculate the elastic torque acting with respect to the first rotation axis zlrwhere rr^ depends on the geometry of the kinematic system 100.

[0054] This way, the kinematic system 100, according to the present invention, allows to generate an elastic torque Meiwith respect to the first rotation axis x±opposite in direction to the gravitational torque Mgand, above all, whose intensity varies with the variation of the angle -dx, compensating during the rotation the variation of the intensity of the gravitational torque Mgand, in particular, replicating the sinusoidal trend of the gravitational torque Mgwith respect to the angle

[0055] In particular, the kinematic system 100 can also comprise a preload device 150 arranged to vary the deformation length of a respective elastic group 116,126,136,146, in order to vary its deformation stiffness.

[0056] With reference to Figs. 5 and 6, the kinematic system 100 according to the present invention can be used to provide an exoskeletal system 200 that allows the assistance to the flexion / extension of a joint of a user, such as for example the shoulder joint. Such exoskeletal system 200 can similarly also be used for the joints of the wrist, fingers, elbow, hip, knee or ankle.

[0057] In particular, the exoskeletal system 200 comprises a single elastic group 146, comprising two torsional springs 146',146'’ placed in series with each other. Furthermore, the exoskeletal system 200 comprises a preload device 150 arranged to vary the connection point between the elasticgroup 146, comprising the two torsional springs 146',146'', and the first link 110, thereby rotating the elastic group 146 around the fourth rotation axis z4.

[0058] Furthermore, the exoskeletal system 200 can make use, as an elastic element 146, of the torsional spring described in patent application W02020 / 104962.

[0059] The foregoing description exemplary 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 as equivalent 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 the weight of a mass (10), said kinematic system (100) comprising: a first link (110) arranged, in use, to be integrally constrained to said mass (10); a second link (120) arranged, in use, to be integrally constrained to a frame (20), said second link (120) being rotatably connected to said first link (110) by means of a first rotational joint (115) having a rotation axis zxorthogonal to a plane 11 and intersecting said plane 11 in a first center of rotation Ox, said mass (10) generating a gravitational torque Mgwith respect to said first rotation axis z1; a third link (130) rotatably connected to said second link (120) by means of a second rotational joint (125) having a second rotation axis z2orthogonal to said plane 11 and intersecting said plane 11 in a second 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 third rotation axis z3orthogonal to said plane 11 and intersecting said plane 11 in a third center of rotation O3, said fourth link (140) being further rotatably connectedto said first link (110) by means of a fourth rotational joint (145) 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 length equal to l2; the segment O2O3has length equal to l3> l2; the segment O3O4has length equal to l4>l2; the segment O4O1 has length equal to l4>l2; the segment O4O1 forms with the segment O4O2an angle equal to T94, arranged to vary with said relative rotation between said first link (110) and said second link (120); the segment O1O2 forms with the segment O2O3an angle equal to I92, arranged to vary with said relative rotation between said second link (120) and said third link (130); the segment O2O3forms with the segment O3O4an angle equal to T93, arranged to vary with said relative rotation between said third link (130) and said fourth link (140); the segment O3O4forms with the segment O4O1 an angle equal to $4, arranged to vary with said relative rotation between said first link (110) and said fourth link (140);said kinematic system (100) characterized in that it is configured in such a way that:If Zi≥ l3and l4> l4then l4+ l2< l3+ Z4;If l3> l4and l3> l4then l3+ l2< l4+ l4;If l4> l4and l4> l3then l4+ l2< l4+ l3; and in that at least one elastic group (116,126,136,146) is provided arranged to generate an elastic torque Metwith respect to said first rotation axis x4opposite in direction to said gravitational torque Mg.

2. The kinematic system (100) for compensating the weight of a mass (10), according to claim 1, wherein a main elastic group (146) is provided arranged to generate an internal torque M4between said first link (110) and said fourth link (140).

3. The kinematic system (100) for compensating the weight of a mass (10), according to claim 2, wherein an auxiliary elastic group (116) is provided arranged to generate an internal torque M4between said first link (110) and said second link (120).

4. The kinematic system (100) for compensating the weight of a mass (10), according to claim 2, wherein an auxiliary elastic group (126) is provided arranged to generate an internal torque M2between said second link (120) and said third link (130).

5. The kinematic system (100) for compensating the weight of a mass (10), according to claim 2, wherein an auxiliary elastic group (136) is provided arranged to generate an internal torque M3between said third link (130) and said fourth link (140).

6. The kinematic system (100) for compensating the weight of a mass (10), according to any of claims from 1 to 5, wherein at least one elastic group (116,126,136,146) comprises a torsional spring.

7. The kinematic system (100) for compensating the weight of a mass (10), according to any of claims from 1 to 5, wherein at least one elastic group (116,126,136,146) comprises two springs arranged in parallel.

8. The kinematic system (100) for compensating the weight of a mass (10), according to any of claims from 1 to 5, wherein at least one elastic group (116,126,136,146) comprises two springs arranged in series.

9. The kinematic system (100) for compensating the weight of a mass (10), according to claim 1, wherein 2,9 < Z3 / Z2< 8,6, 2,9 < Z4 / Z2< 6,1, 2,9 < Zi / Z2< 5,7.

10. An exoskeletal system (200) arranged to be made integral with a user, said exoskeletal system (200) comprising the kinematic system (100) according to any of claims from 1 to 9.

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