EP4021367A1

EP4021367A1 - Modular vertebral elements for flexible exoskeletons

Info

Publication number: EP4021367A1
Application number: EP20771356.1A
Authority: EP
Inventors: Jorge FERNÁNDEZ GARCÍA-LLERA; Jesús ORTIZ SÁNCHEZ-LAFUENTE; Luigi MONICA; Francesco DRAICCHIO; Sara ANASTASI
Original assignee: Fondazione Istituto Italiano di Tecnologia; Istituto Nazionale per lAssicurazione contro gli Infortuni sul Lavoro INAIL
Current assignee: Fondazione Istituto Italiano di Tecnologia; Istituto Nazionale per lAssicurazione contro gli Infortuni sul Lavoro INAIL
Priority date: 2019-08-28
Filing date: 2020-08-27
Publication date: 2022-07-06
Also published as: IT201900015159A1; WO2021038481A1

Abstract

An exoskeleton configured to be worn by a user and comprising a plurality of modular vertebral elements (1) connected together along a longitudinal axis by flexible connecting means, each vertebral element (1) comprising a central body (10) provided with a supporting surface (100) on the user's body and a free surface (101) opposite said supporting surface. The exoskeleton comprises a cable (2) engaged with at least two vertebral elements (1), at least some vertebral elements (1) being provided with means for guiding said cable (2) and with a spacing member of said guiding means from said free surface (101).

Description

MODULAR VERTEBRAL ELEMENTS FOR FLEXIBLE EXOSKELETONS

The present invention relates to an exoskeleton configured to be worn by a user and comprising a plurality of modular vertebral elements connected together along a longitudinal axis by flexible connecting means, each vertebral element comprising a central body provided with a supporting surface on the user's body and a free surface opposite said supporting surface. Industrial exoskeletons are robotic devices used as sources of torque to reduce fatigue and effort for workers. Generated by active or passive elements, the torque is transmitted as a force to the body of the exoskeleton wearer, helping to reduce muscle activity and fatigue. In industry, musculoskeletal disorders are a major cause of accidents at work. The majority of the latter are related to lumbar pain, due to compression of the L5-S1 vertebrae. This is why numerous posterior support exoskeletons, also known as lumbar devices or lumbar or spinal exoskeletons, have been developed and marketed in recent years.

The exoskeletons can transmit forces along the wearer's spine, as in the case of passive exoskeletons without rigid frames or perpendicular to the spine, thanks to rigid structures. The latter solution has the advantage of not introducing an additional compressive force on the vertebrae, due to the action of the exoskeleton. However, the reaction forces are also exerted on the thighs and pelvis. Moreover, since the forces are applied only on a limited number of points of application, the magnitude of the forces is significantly high. A further problem with the use of rigid frames is that this solution reduces the user's Range of Motion (RoM), and secondly, the effects of the prolonged application of forces outside the pelvis are still unknown. Recently, new solutions explore the possibility of introducing lighter carbon fibre frames, in order to increase the user's RoM. Furthermore, a lighter exoskeleton is probably more accepted by workers. However, this type of known exoskeleton still applies forces on a limited number of points.

Finally, exoskeletons exist as described above, characterized by modularity and flexible connections in order to be ergonomic and lightweight. These exoskeletons are biomimetic: this implies that the modular elements, also by adhering to the user's body, do not hinder movements. To meet this requirement, the frame must provide all degrees of freedom. This is obtained by combining a number of modular elements in series as desired. The resulting frame therefore assumes a non- continuous shape, consisting of modular elements associated with each other.

Document US9492300B2 describes an exoskeleton of this type, used in the military field to redirect loads from the user's back directly to the ground. However, this exoskeleton necessarily involves the user's entire body and is therefore heavy and cumbersome.

The document “Design and Computational Modeling of a Modular, Compliant Robotic Assembly for Human Lumbar Unit and Spinal Cord Assistance” (Gunjan Agarwal, et al. , 31 October 2017) describes another similar exoskeleton, developed on the basis of vacuum-driven pneumatic actuators, therefore characterized by high complexity.

There is therefore at present an unmet need for an exoskeleton which is modular and provided with flexible connections, which is light and constructively simple, which can be implemented both actively and passively and which transmits forces perpendicular to the user's body on a large surface.

The present invention aims to overcome the aforementioned disadvantages of the state of the art with an exoskeleton as described above, which further comprises a cable engaged with at least two vertebral elements, at least some vertebral elements being provided with means for guiding said cable and with a spacing member of said guiding means from said free surface.

In this manner, it is possible to connect the cable to a source of force and transmit the forces in a direction perpendicular to the user's body through the contact surfaces of the vertebral elements. The presence of the spacing member allows to obtain a distance between the point of application of the force from the cable and the central body of the vertebral element in contact with the user's body. This allows the transmission of force exerted by the force source to be influenced simply by varying the geometrical properties of the components of the vertebral elements.

In an embodiment, the spacing member consists of a fork comprising two arms extending in an opposite direction to the user starting from said free surface, said arms supporting said guiding means.

In a further embodiment, said guiding means comprise two or more pulleys engaged between the two arms in a neutral rotatable manner about the relative rotation axis thereof.

The presence of pulleys allows the cable to slide freely without friction problems, while exerting forces on precise points of the arms.

According to an embodiment, the pulleys have an axis of rotation perpendicular to the user's sagittal plane when wearing the exoskeleton and each vertebral element comprises at least one lower pulley and one upper pulley, respectively positioned below and above when wearing the exoskeleton, the cable being placed in contact with the upper pulley part facing said free surface of the central body and with the lower pulley part facing opposite said free surface of the central body.

In a further embodiment, the lower pulley and the upper pulley have different distances from the longitudinal axis of the exoskeleton.

According to one embodiment, the arms are tilted downwards when wearing the exoskeleton.

The features described above make it possible to better adjust the distribution of forces, as explained in detail below.

In a preferred embodiment, the arms have an inclination of 45° with respect to the plane in which the central body lies.

This value has proved to be optimal to maximize the transmitted torque and minimize the overall dimensions of the device. ln one embodiment, the central body is provided with lateral wings in contact with the user's body.

In this manner, the supporting surface of the single vertebral element on the user's body is enlarged, to avoid localized pressures. In a further embodiment, said flexible connecting means comprise a tubular element.

This makes it possible to provide a plurality of vertebral elements placed in series, connected to each other by the tubular element, in a configuration in which two consecutive vertebral elements are spaced from an intermediate zone in which only a section of the tubular element is present.

According to an improvement, a single tubular element is provided to which the vertebral elements are fixed.

This gives strength to the entire exoskeleton, in addition to greater constructional simplicity.

In a first embodiment, said cable is at least partially elastic.

In this manner the cable is tensioned by the elastic features thereof and passively acts on the vertebral modules.

In a second embodiment, said cable is actuated by an actuator. In this manner, the actuation of the exoskeleton is of the active type.

The structural features of the exoskeleton therefore allow both active and passive implementation.

The exoskeleton object of the present invention is therefore flexible, ergonomic and lightweight and allows an improved distribution of forces and torques delivered by the actuation system on the user's body. The modularity of the constituent elements allows to obtain a reconfigurable exoskeleton.

The exoskeleton mimics the performance of the human spine and may be actively or passively actuated to correct the user's posture or to support movement by at least partially relieving the L5-S1 intravertebral joint. The risk of back injury can be reduced by applying a pulling force on the upper back and a pushing force on the hip region during spinal flexion/extension.

In the case of a passive actuation, a clutch or damping member can be provided, to allow the modulation of the actuation.

Given the lightweight structure of the exoskeleton, combined with the modularity and high user acceptability thereof thanks to the freedom of movement guaranteed, the fields of application are not limited only to the industrial field, but can also be extended to waste collection, logistics, healthcare and so on. In addition, it is easy to combine several vertebral elements in a single exoskeleton, considering the modularity that distinguishes them. Therefore, this makes it possible to build and develop different sections, each aimed for example at lumbar assistance, upper limb and lower limb assistance, and to integrate them with each other. These and other features and advantages of the present invention will become clearer from the following description of some non-limiting exemplary embodiments illustrated in the attached drawings in which: fig. 1 shows a vertebral element; fig. 2 shows an orthogonal projection of the vertebral element; figures 3 and 4 show an assembled and exploded view of two vertebral members provided with pulleys, respectively; fig. 5 shows an orthogonal projection of two vertebral elements provided with pulleys; fig. 6 shows a pair of vertebral elements with the cable engaged in the respective pulleys; figures 7 and 8 show the relative movements between two adjacent vertebral elements under the action of the cable; figures 9, 10, 11 and 12 schematically show the distribution of forces as the geometry of the vertebral element changes; figures 13, 14 and 15 show possible movements of the exoskeleton; fig. 16 shows a partially exploded view of an embodiment of the exoskeleton when worn. Figure 1 shows a single modular vertebral element 1 which forms the fundamental unit for assembling an exoskeleton configured to be worn by a user according to the present invention. The exoskeleton comprises a plurality of modular vertebral elements 1 connected to each other along a longitudinal axis by flexible connecting means: in the assembled condition of the exoskeleton, the vertebral elements 1 are then placed in series to form a chain. The number of vertebral elements 1 can be varied as desired based on design needs.

Each vertebral element 1 comprises a central body 10 provided with a supporting surface 100 on the user's body and a free surface 101 opposite said supporting surface 100. The vertebral element 1 is provided with lateral wings 11 in contact with the user's body, which lateral wings 11 increase the area of the supporting surface 100 by increasing the applied assistive forces and depart on opposite sides from the central body 10. The vertebral element 1 is therefore symmetrical with respect to the longitudinal axis along which the exoskeleton extends.

The vertebral element is preferably made of plastic to ensure lightness and durability at low costs, but can be made of other materials, preferably light, such as metal alloys, carbon fibre, etc. The vertebral element 1 further comprises a fork 12 consisting of a pair of arms 120 extending from the central body 10 in the opposite direction to the wearer when wearing the exoskeleton, starting from the free surface 101. Preferably the arms 120 consist of plate-shaped elements lying on two planes parallel to each other and parallel to the sagittal plane of the wearer when wearing the exoskeleton.

As can be seen in figures 3 and 4, in the area interposed between the two arms 120, two pulleys 13 are engaged in an idle, rotatable manner about the relative rotation axis thereof. For fixing the pulleys 13, each arm 120 is provided with two through holes housing fixing screws 130. The pulleys 13 thus have an axis of rotation perpendicular to the sagittal axis of the user when wearing the exoskeleton. The pulleys 13 may be of any currently known type, preferably consisting of idly rotatable engaged return rollers by means of bearings on the fixing screws 130. The exoskeleton comprises a cable 2 engaged with the vertebral elements 1 by means of the pulleys 13. The pulleys 13 therefore constitute cable guiding means 2 and the fork 12 acts as a pulley spacing member 13 from the free surface 101. Acting on the pulleys, the cable transmits forces and torques to each vertebral element 1 and consequently to the user's body.

Each vertebral element 1 comprises a lower pulley 13’ and an upper pulley 13”, respectively positioned below and above when the exoskeleton is worn. As shown in figure 6, the cable 2 is placed in contact with the upper pulley part 13” facing the free surface 101 of the central body 10 and with the lower pulley part 13’ facing away from the free surface 101 of the central body 10. The cable 2 thus passes above the lower pulley 13’ and below the upper pulley 13”. In this manner, once mechanical tension is applied to the cable 2, each vertebral element 1 tends to rotate clockwise in the view shown in figures 7 and 8.

Thanks to the relative angle between the vertebral elements 1 and the path of the cable, more detailed in the subsequent figures, it is possible to transmit forces and moments between two vertebral elements 1 and return the system to the initial position simply by putting the cable 2 in traction.

The manner in which the mechanical tension of the cable 2 is generated is not the object of this invention. However, it is possible, by way of example, to provide an elastic cable directly passing between the pulleys to generate an elastic tension, or a cable having elastic portions or connected to springs. In this way the cable 2 passively acts on the vertebral modules 1.

Alternatively, the cable 2 can be connected to an actuator, for example an electric motor with coil rewinder. In this manner, the actuation of the exoskeleton is of the active type. The lower pulley 13’ and the upper pulley 13” have different distances from the longitudinal axis of the exoskeleton, as seen for example in figures 7 and 8, in particular the lower pulley 13’ has a greater distance with respect to the upper pulley 13”. A single arm 120 can be outlined as in figures 9, 10, 11 and 12, where only the centres of the pulleys 13 (A, B) and the base point on the central body 10 around which the rotation (C) occurs are shown. Assuming that on the centres of the pulleys 13 the reaction forces Fa and Fb act with an inclination a and b with respect to the longitudinal axis of the exoskeleton (shown horizontally in the figures), the angular inclination of the arm 120 (Q) influences the torque calculated in C. In fact, by fixing the vertical movement of A and B with respect to C and the horizontal movement of B with respect to A, the equation below shows how Q influences the moment calculated in C:

M_c = F_AxA_y + F_AyA_x + F_BxB_y + F_ByB_x where (A_x, A_y, B_x, B_y) represent the torque arms, as shown in figure

10.

From the above equation it follows that Me is different if calculated for the configuration of figure 9 or for that of figure 10.

The choice of the optimal inclination value of the arm 120 is not trivial, as it should take into account both the relative rotations of the vertebral elements 1 and how the forces are applied on the pulleys 13. In principle, Q could assume any value between 0° and 90°. Preferably the arms 120 are inclined downwards when the exoskeleton is worn. In the embodiment shown in the figures, the arms 120 have an inclination Q of 45° with respect to the plane on which the central body 10 lies, i.e. , with respect to the longitudinal axis of the exoskeleton, in order to simultaneously maximize the torque and minimize the overall dimensions of the device. The arms 120 thus advantageously assume a parallelogram shape.

The angles defining the directions of the forces acting on the pulleys 13 (a and b) are influenced by the geometric values of the pulleys 13 themselves and the relative angular inclination of the vertebral elements 1 relative to each other, as schematically shown in figures 11 and 12, in which the positions of the pulley centres 13 are modified between one configuration and the other. The vertebral elements 1 are connected to each other by flexible connecting means. Such means may be of any currently known type and preferably consist of a tubular element 3, in particular a single tubular element 3 to which the vertebral elements 1 are fixed. To ensure flexibility, the tubular element 3 can advantageously be of yielding plastic material.

The tubular element 3 is preferably integrated within the vertebral elements 1, in particular in the central body 10, and thus runs longitudinally along the entire exoskeleton. In the space interposed between two successive vertebral elements 1, the tubular element 3 forms the only connection between the two different vertebral elements 1 , so that the two vertebral elements 1 are separated from each other by a space in which only the tubular element 3 is present, as visible for example in figure 5. Thanks to the flexibility of the tubular element 3 and the distance of the individual vertebral elements 1 from each other, the assembled exoskeleton allows great freedom of movement as shown in figures 13, 14 and 15, in which the lateral flexion, extension/flexion and rotation movements along the longitudinal axis are respectively visible. The vertebral elements 1 can be combined with each other to form the structure of a posterior or spinal support exoskeleton as shown in figure 16. In the embodiment in the figure, the exoskeleton extends between the user's thighs and chest. In particular, the exoskeleton comprises three sectors, two lower sectors for the legs and one upper one for the back, each consisting of a series of vertebral elements 1 connected together by a tubular element 3 and actuated by a cable 2. The three sectors of the exoskeleton are connected to each other in an intermediate zone provided with supporting plates 4 for the user's buttocks. Considering human anatomy, the Gluteus Maximus is the central muscle connecting the legs and back with the most surface near the waist and hip, justifying the choice of applying forces to this anatomical region.

The exoskeleton shown appears to be a complex flexible structure preferably made of plastic, i.e. , a light and resistant material, which perfectly adapts to the human body. Plastic is cited merely by way of example, but in principle any light and resistant alloy could be used. Being formed by individual modular vertebral elements, the exoskeleton achieves an exceptional level of freedom of movement, allowing all types of movement involved during bending and crouching manoeuvres, as well as other movements not related to lifting tasks, such as walking.

The total weight of the exoskeleton shown in the figure can be very low, in particular less than 2 kg.

Finally, it is interesting to highlight how it is possible to increase the number of vertebral elements 1 which form the exoskeleton to further distribute forces and torques along the longitudinal axis of the exoskeleton.

Claims

1. An exoskeleton configured to be worn by a user and comprising a plurality of modular vertebral elements (1) connected together along a longitudinal axis by flexible connecting means, each vertebral element (1) comprising a central body (10) provided with a supporting surface (100) on the user's body and a free surface (101) opposite said supporting surface, characterized in that it comprises a cable (2) engaged with at least two vertebral elements (1), at least some vertebral elements (1) being provided with means for guiding said cable (2) and with a spacing member of said guiding means from said free surface (101).

2. The exoskeleton according to claim 1, wherein the spacing member consists of a fork (12) comprising two arms (120) extending in an opposite direction to the user starting from said free surface (101), which arms (120) supporting said guiding means.

3. The exoskeleton according to claim 2, wherein said guiding means comprise two or more pulleys (13) engaged between the two arms (120) in an idle, rotatable manner about the relative rotation axis thereof.

4. The exoskeleton according to claim 3, wherein the pulleys (13) have an axis of rotation perpendicular to the user's sagittal plane when wearing the exoskeleton and each vertebral element (1) comprises at least one lower pulley (13’) and one upper pulley (13”), respectively positioned below and above when wearing the exoskeleton, the cable (2) being placed in contact with the upper pulley part (13”) facing said free surface (101 ) of the central body (10) and with the lower pulley part (13’) facing away from said free surface (101 ) of the central body (10).

5. The exoskeleton according to claim 4, wherein the lower pulley (13’) and the upper pulley (13”) have different distances from the longitudinal axis of the exoskeleton.

6. The exoskeleton according to claim 4 or 5, wherein the arms (120) are inclined downwards when the exoskeleton is worn.

7. The exoskeleton according to claim 6, wherein the arms (120) have an inclination of 45° with respect to the plane on which the central body (10) lies.

8. The exoskeleton according to one or more of the preceding claims, wherein the central body (10) is provided with lateral wings (11) in contact with the user's body.

9. The exoskeleton according to one or more of the preceding claims, wherein said flexible connecting means comprise a tubular element (3).

10. The exoskeleton according to claim 9, wherein a single tubular element (3) is provided to which the vertebral elements (1) are fixed.

11. The exoskeleton according to one or more of the preceding claims, wherein said cable (2) is at least partly elastic.

12. The exoskeleton according to one or more of the preceding claims, wherein said cable (2) is actuated by an actuator.