Kinematic chain to assist flexion-extension of a joint

DESCRIPTION

Field of the invention

The present invention relates to the field of robotic exoskeletons for orthopedic rehabilitation.

In particular, the invention relates to a modular kinematic chain for assisting the movement of an anatomical joint.

Description of the prior art

In the wearable robotics sector, the need is increasingly felt to find a simple and efficient architecture to create exoskeletons to assist in the movement of anatomical joints, such as the set of phalanges that make up the finger of the hand.

To date, although there are numerous exoskeletons that deal with the issue of mobilization, the still very important technical problem concerns the size and weight of these devices, which prevent a truly natural movement experience for the user.

Furthermore, exoskeletons for assisting joints such as those of the hand are very complex from the kinematic point of view, because they must have a rotational effect on the anatomical joints through a kinematics that is not aligned with the joint, but rather disposed above or sideways. This frequently leads to the undesirable generation of parasitic force on the bone segments, which lower the comfort of use and the effectiveness in handling assistance.

It is therefore of great importance to find a kinematic chain with little lateral encumbrance able to follow the flexion-extension movement of the hand well, accompanying and assisting the movement.

In WO2014033613 an exoskeletal device is proposed for assisting the movement of a metacarpal-phalangeal joint of a hand, comprising a metacarpal support, a phalangeal support and a kinematic chain between the metacarpal support and the phalangeal support. This kinematic chain in turn comprises a metacarpal sled, a rigid link rotatably connected to the metacarpal sled by means of a first rotoidal constraint, a second rotoidal constraint between the rigid link and the phalangeal support, and actuation means for imposing a first rotation on the rigid link and a second rotation to the support.

However, this solution has a high stiffness, resulting in both a low adaptability to the anthropometric dimensions of the user, and the generation of parasitic constraining forces on the phalanges due to the fact that the exoskeleton is unable to faithfully follow the movement of the rotation axes of the anatomical joints during finger flexion- extension.

Summary of the invention

It is therefore a feature of the present invention to provide a kinematic chain for assisting the movement of an anatomical articulation that allows to faithfully follow the movement of the rotation axes of the anatomical joints during the movement of the joint itself.

It is also a feature of the present invention to provide such a kinematic chain that allows to adapt to different anthropometric measurements of the user not known a priori.

It is still a feature of the present invention to provide such a kinematic chain that has limited bulk and weight with respect to prior art solutions.

It is a further feature of the present invention to provide such a kinematic chain that allows one or more modules to be placed in series to adapt to different joints and medical conditions.

These and other objects are achieved by a kinematic chain for assisting the movement of an anatomical articulation according to claims from 1 to 11.

Such solution allows to place in series a number n of rotating elements that can be varied according to the specific use and the type of articulation to be assisted. For example, in a basic configuration, it is possible to use a single rotating element (n = 1) and a roto- translation constraint between the elongated element and the end element. In this case, between the end element and the frame, i.e. between the two engagement portions constrained to the anatomical portions upstream and downstream of the articulation, there is a roto-translation constraint in which the displacement of the instantaneous center of rotation between the elongated element and the frame and the translation between the elongated element and the terminal element allow the correct alignment of the kinematic chain with the anatomical portions, allowing free movement of the articulation without having parasitic forces discharged on the articulation itself, up to a certain value of the rotation of the anatomical joint.

In case that the anatomical joint must perform a greater rotation, it is possible to increase the number of rotating elements (n > 3) and, if necessary, to remove the roto- translation constraint between the elongated element and the end element.

Furthermore, depending on the distance between the anatomical portions upstream and downstream of the articulation and the maximum angle to be achieved, it is possible to use rotating elements that have different values of r¾ and r[, so as to vary the relative rotation that each rotating element performs with respect to the previous element.

The kinematic chain according to the present invention, therefore, allows to provide assistance by adapting to any type of joint and anthropometric measurement, without generating parasitic constraint reactions on the patient's articulations.

Furthermore, the actuation of the kinematic chain can be made by means of a system of cables and pulleys, or by the actuation of a single rotating element.

In particular, in the event that the transmission of motion between the elements of the chain is achieved by means of toothed profiles, the actuation can be achieved by engaging an actuator with a rotating element.

A further advantage of the present invention resides in the fact that it is possible to place a plurality of kinematic modules in series, by means of roto-translation constraints, to assist all the articulations of a polyarticular joint, such as, for example, a finger or the vertebral column.

Brief description of the drawings

Further characteristic and/or advantages of the present invention are more bright with the following description of an exemplary embodiment thereof, exemplifying but not limitative, with reference to the attached drawings in which: Fig. 1 schematically shows the operating principle of a module of the kinematic chain, according to the present invention, in the case

Fig. 2 schematically shows the operating principle of a module of the kinematic chain, according to the present invention, in the case

Figs. 3A and 3B schematically show the opposite sides of a possible embodiment of a module of the kinematic chain, according to the present invention, where the profiles of the rotating elements, of the frame and of the elongated element are toothed profiles arranged to mesh with each other;

Fig. 4 shows the embodiment of Figs. 3A and 3B with non-zero relative rotations;

Figs. 5A and 5B show the opposite sides of a possible embodiment of a module of the kinematic chain, according to the present invention, in which an actuation system comprising a cable and 3 pulleys is also shown;

Fig. 6 shows a perspective view of the embodiment of Figs. 5A and 5B;

Fig. 6A shows a detail of Fig. 6;

Figs. 7A and 7B show the opposite sides of a possible embodiment of a module of the kinematic chain, according to the present invention, in which rotating redundancy elements are provided;

Fig. 8 shows a perspective view of the embodiment of Figs. 7A and 7B wherein an end element of a first module is made integral with the frame of a second module to place the two modules in series;

Fig. 8A shows a detail of Fig. 8;

Fig. 9 shows an embodiment of the kinematic chain, according to the present invention, wherein three kinematic modules are placed in series by means of the coupling system shown in Figs. 8 and 8A.

Description of a preferred exemplary embodiment

With reference to Figs. 1, 2, 3 and 4, the kinematic chain for assisting the movement of an anatomical articulation comprises at least one kinematic module 100 comprising a frame 105 having a first end 106, comprising a first engaging portion 180 arranged to be integrally connected to a proximal anatomical portion with respect to the articulation, and a second end 106' comprising a profile and a centre of rotation .

The kinematic module 100 then comprises a number n of rotating elements, defined by an index i= 1,...,n. Each i-th rotating element has a first end, comprising a profile Pi and a centre of rotation 0 _i , and a second end, comprising a profile and a centre of rotation .

The kinematic module 100 also comprises an elongated element 140 having a first end 141 comprising a profile P _n+1 and a centre of rotation 0 The elongated element 140 is constrained at one end element 107 comprising a second engaging portion 180' arranged to be integrally connected to a distal anatomical portion with respect to the articulation.

In particular, Figs. 1, 2, 3 and 4 show the solution with n = 3. Therefore: the rotating element i = 1 corresponds to the rotating element 110 and comprises a first end 111, comprising a profile P ₁ and a centre of rotation 0 ₁ and a second end 111', comprising a profile and a centre of rotation 0 ; the rotating element i = 2 corresponds to the rotating element 120 and comprises a first end 121, comprising a profile P ₂ and a centre of rotation 0 ₂ , and a second end 121', comprising a profile and a centre of rotation ,' the rotating element i = 3 corresponds to the rotating element 130 and comprises a first end 131, comprising a profile P ₃ and a centre of rotation 0 ₃ , and a second end 131', comprising a profile and a centre of rotation ; the elongated element 140 has a first end 141 comprising a profile P ₄ and a centre of rotation 0 ₄ .

In particular, the frame 105, the rotating elements

110,120,130 and the elongated element 140 are arranged on parallel planes in an alternating manner.

To show the arrangement on parallel planes of the elements of the module 100, in Figs. 1 and 2 the frame 105, the rotating element 120 and the elongated element 140 are partially transparent and show the rotating elements 110 and

130 arranged in the underlying plane.

In particular, the reference plane π ₀ , passing through the centre of rotation of the frame 105, is coplanar to the plane π ₂ , passing through the centres of rotation 0 ₂ and of the rotating element 120, and to the plane π ₄ , passing through the centre of rotation 0 ₄ of the elongated element

140. Similarly, the plane π ₁ passing through the centres of rotation and of the rotating element 110, is coplanar to the plane π ₃ , passing through the centres of rotation 0 ₃ and of the rotating element 130, and both planes π ₁ and π ₃ are parallel to the planes π ₀ , π ₂ and π ₄ .

Furthermore, the kinematic module 100 is configured in such a way that the rotating element 110 is constrained to make a relative rotation with respect to the frame 105 about an axis passing through the centres of rotation and overlapped to each other and arranged, respectively, on the parallel planes π ₁ and π ₀ . This way, the relative rotation lies in the reference plane π ₁ .

Similarly, the rotating element 120 is constrained to carry out, in the reference plane π ₂ , a relative rotation with respect to the rotating element 110 about an axis passing through the centres of rotation 0 ₂ and while the rotating element 130 is constrained to carry out, in the reference plane TT ₃ , a relative rotation with respect to the rotating element 120 about an axis passing through the centres of rotation 0 ₃ and , and the elongated element 140 is constrained to carry out, in the reference plane π ₄ , a relative rotation with respect to the rotating element 130 about an axis passing through the centres of rotation 0 ₄ and -

Furthermore, the profiles and P _n+1 are suitably in contact to each other at points C ₁ C ₂ and C ₃ . Such contact can generate a friction constraint which is adapted to transmit a pure rolling motion, as in the case of Figs. 1 and

2, or can be a contact between toothed profiles, as in the case of Figs. 3A to 9.

In both cases, the distance between the various centres of rotation and O _n+1 and the respective points of contact C _lf C ₂ and C ₃ between elements of the module 100 are defined by the general relations:

In particular, in the case shown of n = 3, we have:

If the profiles and P _n+1 are circular toothed profiles having centres of curvature coincident with said respective centres of rotation , the quantities are the pitch radiuses of such circular toothed profiles.

In all an embodiments shown, the contact at points C _1,

C ₂ and C ₃ is adapted to transmit a rotational movement without slipping between the frame 105, the rotating elements

110,120,130 and the elongated element 140, verifying the equation: with i= 1,

Therefore, in the case n = 3 we have:

This equation constrains the relative angles between the various elements of the kinematic chain, allowing to operate a single rotation to move all the elements of the chain in a predetermined manner.

In particular, in the case of Fig. 1 and of Figs. 3A to 9, the elements are in such a way that have and therefore

In Fig. 2 is shown instead an embodiment in which implying the relations:

The embodiment of Fig. 2 allows to have a constant angular increase in the rotation of the various elements of the module 100, allowing to reach, with the same elements of the module and with the same value of , a relative angle between the elongated element 140 and the frame 105 greater than the embodiment of Fig. 1.

With reference to Figs. 5A and 5B, in an application embodiment of the present invention, the kinematic module 100 further comprises an actuation system comprising a cable 171 and three pulleys 172 suitable for generating the relative rotations Furthermore, as shown in Figs. 6 and 6A, this exemplary embodiment provides a constraint of roto-translation between the second end 14V of the elongated element and the end element 107. This way, the kinematic module 100 can follow with higher precision the movement of the anatomical joint of the articulation during the rotation.

Figs. 7a and 7b show a possible embodiment of the module

100, wherein redundancy rotating elements 110' and 130' are provided on the opposite side with respect to the rotating elements 110 and 130. In this way, there is a greater structural solidity of the cinematic chain.

Fig. 9 shows an embodiment of the kinematic chain 10, wherein three modules kinematic 100a, 100b and 100c are placed in series, by the coupling system shown in Figs. 8 and 8A.

This coupling system provides that a terminal element 107 of a first module 100a is made integral with the frame 105 of a second module 100b and so on. In this way, between the modules placed in series there is a roto-translation constraint that allows to follow with greater precision the movement of the anatomical joints during the movement of the polyarticular segment, such as for example a flexion-extension of a finger of a hand.

The foregoing description some exemplary specific embodiments 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 in various applications the specific exemplary embodiments without further research and without parting from the invention, and, accordingly, it is meant 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.