Backbone structure for exoskeleton

Abstract

One aspect of the invention relates to a backbone structure (100) for an exoskeleton comprising: a beam (110) having a length (115) and a cross-section, the cross-section having a major dimension and a minor dimension, a first fixed connection (120) with the exoskeleton located at a first end (113) of the beam (110), and a second connection (130) with the exoskeleton located at a second end (114) of the beam (110) of sliding pivot type. Figure to be published with the abstract: Figure 1

Description

Title of the invention: Back structure for exoskeleton TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of walking assistance exoskeletons.

[0002] The present invention relates to a dorsal structure for an exoskeleton. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] An exoskeleton is a device attached to one or more limbs of the human body to restore mobility or increase physical capabilities.

[0004] Exoskeletons can assist a human in various tasks such as carrying heavy loads, walking, running, etc. Many applications are possible, for example in the medical, industrial or military fields.

[0005] Depending on the intended applications, exoskeletons differ greatly. Thus, it is possible to divide exoskeletons into two main categories.

[0006] A first category concerns passive exoskeletons. Passive exoskeletons are not motorized. Passive exoskeletons incorporate materials and equipment for storing and releasing energy during the user's movement. The term "user" refers to the person wearing the exoskeleton. This person can be a man or a woman of any age. Passive exoskeletons are often used for ergonomic purposes, to prevent repeated microtraumas or to help lift tools or equipment. Thus, passive exoskeletons, such as that disclosed in patent application WO2014109799A1, are mainly intended to assist able-bodied people in performing a repetitive and / or traumatic task.

[0007] A second category of exoskeletons concerns active exoskeletons. Active exoskeletons rely on systems such as motors, hydraulic or pneumatic systems, capable of increasing human strength or reducing the body's energy consumption. An active exoskeleton consists of one or more actuators, which can be an electric motor for example. The actuator actively increases the power of the human body.

[0008] Generally speaking, active exoskeletons are heavier than passive exoskeletons, due to the amount of equipment and accessories they incorporate. The weight of the active exoskeleton makes it uncomfortable to use. In addition, active exoskeletons, such as the one presented in patent US11185460B2, generally greatly limit the mobility of the user.

[0009] Active walking assistance exoskeletons actively participate in the flexion and extension of the user's hip. These exoskeletons include an actuator located near the hip and generating a torque around the flexion / extension axis of the hip. These exoskeletons also include a belt to which the actuators are attached. In addition, it is known to use a harness at the bust. The harness makes it possible to transmit the reaction forces of the hip assistance generated by the actuators. The simplified resulting force is a quasi-normal force to the user's bust in the sagittal plane, forward or backward depending on the direction of assistance. Transmitting the force to the belt and to the bust rather than only the belt makes it possible to increase the lever arm, and therefore to reduce the equivalent felt force.

[0010] In order to connect the harness and the belt of the exoskeleton, patent US10766134B2 proposes a dorsal structure inspired by the functioning of the human spine. This dorsal structure comprises a plurality of vertebral elements, stacked on top of each other, and a flexible connecting element connecting the vertebral elements to each other. This structure has several drawbacks. Firstly, due to the large number of parts composing it, it is complex and expensive to manufacture. In addition, this dorsal structure is heavy. Finally, it greatly limits the lateral flexion movements, also called abduction and / or adduction, of the torso and torsion of the torso. This dorsal structure is therefore not suitable for use in an exoskeleton adapted for assistance during walking and in particular during mountain hiking.

[0011] There is therefore a need to provide a dorsal structure for an exoskeleton limiting the aforementioned drawbacks. Summary of the invention

[0012] The invention offers a solution to the problems mentioned above by providing a dorsal structure suitable for use within an exoskeleton. The dorsal structure comprises a beam for transmitting the reaction forces of the hip assistance generated by actuators of the exoskeleton while allowing sufficient freedom of movement to the torso of a user of the exoskeleton. Indeed, due to the size of its large dimension, the beam is sufficiently rigid in the sagittal plane of the user to ensure effective transmission of the forces generated by the actuators of the exoskeleton. In addition, due to the size of its small dimension, the beam allows lateral flexion mobility of the user's torso and, to a lesser extent, torsion of the user's torso.The slide-type connection located at one end of the beam also ensures sufficient mobility when the exoskeleton user bends forward or performs a . hip flexion. The slide-type connection finally allows the back structure to adapt to a possible difference in size between different users of the exoskeleton.

[0013] One aspect of the invention relates to a dorsal structure for an exoskeleton comprising: • a beam having a length and a cross-section, the cross-section having a major dimension and a minor dimension, • a first fixed connection with the exoskeleton located at a first end of the beam, and • a second connection with the exoskeleton located at a second end of the slide-type beam.

[0014] The dorsal structure according to the invention is suitable for use within an exoskeleton. In one example, the dorsal structure according to the invention is suitable for use within an exoskeleton suitable for assisting walking and in particular for assisting mountain hiking. Thus, the dorsal structure according to the invention is comfortable, in particular because it is light, to allow intensive walking lasting several hours. In addition, the dorsal structure according to the invention allows the user to maintain freedom of movement during walking assistance. Finally, the dorsal structure is reliable and simple to manufacture so that it can be used by a large number of amateur sportsmen.

[0015] In addition to the characteristics which have just been mentioned in the preceding paragraph, the backbone structure according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the second connection is of the sliding pivot type, • the second connection comprises a degree of freedom in rotation adapted to allow rotation around a connection axis of the second connection between -45° and 45°, • the connecting axis of the second connection further forms an angle of between 120° and 180° with the length of the beam, the angle formed being in a longitudinal section of the beam, • the beam has a first bending resistance in the plane perpendicular to the face of the large dimension of between 5 and 50 newtons and a second bending resistance in the plane perpendicular to the face of the small dimension of between 50 and 300 newtons, • the large dimension of the beam is between 10 and 50 millimeters and the small dimension of the beam is between 1 and 10 millimeters, • the length of the beam is between 50 millimeters and 300 millimeters, • the second connection is implemented by a smooth or ball bearing coupled to a smooth ground cylinder of revolution, • a smooth ground cylinder of revolution length is between 50 and 400 millimeters, • the beam (110) is made of composite with: • carbon fibers, or • glass fibers, or • Kevlar fibers, or • flax fibers.

[0016] Another aspect of the invention relates to an exoskeleton for assisting a user in walking, comprising: • right and left actuators assisting a flexion and extension movement respectively of a right and left hip of the user, the right and left actuators being attached to a lumbar belt adapted to surround a waist of the user, • A chest harness adapted to encircle a user's torso, and • A back structure according to any one of the preceding claims, the back structure being linked to the lumbar belt by the first connection and to the chest harness by the second connection.

[0017] The exoskeleton according to the invention is suitable for assisting walking and in particular for hiking in the mountains. In particular, thanks to the presence of a dorsal structure according to the invention, the exoskeleton allows a distribution of the forces linked to assisting walking. Thus, the equivalent felt force is distributed between the lumbar belt and the chest harness. This makes it possible to improve the comfort of use of the exoskeleton. In addition, the presence of the dorsal structure according to the invention in the exoskeleton also allows the user to maintain freedom of movement, in particular for lateral flexion movements of the torso.

[0018] In addition to the characteristics which have just been mentioned in the preceding paragraph, the exoskeleton according to one aspect of the invention may have a chest harness comprising a rigid plate linked to the second connection.

[0019] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0020] The figures are presented for information purposes only and in no way limit the invention. • Figures 1, 2 and 3 show a schematic representation, from different points of view, of an example of a backbone structure according to the invention. • [Fig.4] shows a schematic representation of an example of a sliding pivot type connection included in the backbone structure according to the invention. • [Fig.5] shows a schematic representation of an example of an exoskeleton according to the invention. • [Fig.6] shows a schematic representation of an example of a beam according to the invention. DETAILED DESCRIPTION

[0021] [Fig. 1] shows a schematic representation from a first point of view of an example of a backbone structure 100 according to the invention. [Fig. 2] shows a schematic representation from a second point of view of an example of a backbone structure 100 according to the invention. [Fig. 3] shows a schematic representation from a third point of view of an example of a backbone structure 100 according to the invention.

[0022] The backbone structure 100 comprises a beam 110 having a length 115 and a cross-section. The term "length" may designate in the present application the main or longitudinal axis of an element such as the beam. The terms "main axis" designate in the present application the main axis of inertia. The cross-section is a planar surface perpendicular to the length 115 of the beam. The shape of the cross-section may be any geometric shape that can be characterized by the size of a first dimension and the size of a second dimension. The two dimensions are measured in two non-parallel directions and preferably in two orthogonal directions. The cross-section may for example be a polygon or an ellipse. When the cross-section is a polygon, the cross-section may be a polygon inscribed in an ellipse or preferably a convex polygon inscribed in an ellipse.The cross-section may for example be a polygon such as a rectangle or a parallelogram. When the cross-section is a rectangle, the first dimension may be the length of the rectangle and the second dimension may be the width of the rectangle. When the cross-section is a parallelogram, the first dimension may be the base of the parallelogram and the second dimension may be the height of the parallelogram. The cross-section may also be a triangle or a polygon having at least five sides. When the cross-section is an ellipse, the first dimension may be the major axis of the ellipse and the second dimension may be the minor axis of the ellipse. The cross-section may further vary along the length of the beam. In other words, depending on its distance from a first end 113 of the beam, the cross-section may vary. The variation of the cross-section may relate to the size of the first dimension and / or the size of the second dimension of the cross-section. The variation in size may be proportionally the same for both dimensions or differentiated. Complementarily and / or alternatively, the variation may relate to the type of the geometric shape of the beam. For example, the cross-section may be a rectangle at the first end 113 and a hexagon or an ellipse at a second end 114. The variation in the size of the dimensions and / or type of geometric shape may be made proportionally depending on the distance from the first end 113.Alternatively, the variation in the size of the dimensions and / or type of geometric shape may be carried out in a non-proportional manner depending on the distance from the first end 113 or even abruptly, i.e. without transition from one dimension to another or from one type of geometric shape to another.

[0023] The beam has a first end 113 and a second end 114. The term "end" refers to the portions of the beam 110 located at the lengthwise ends of the beam. In one example, illustrated in [Fig.l], consistent with previous examples, the beam includes a first end 113 and a second end 114 of the beam. For example, the first end 113 is the end of the beam near the user's pelvis and the second end 114 of the beam is the end near the user's shoulder blades. As illustrated in [Fig.l], the beam 110 may be adapted so that the length of the beam 110 extends along the spine of a user of the exoskeleton. Thus, the direction of the beam 110 in its length may be substantially vertical when the user is in the reference anatomical position.The terms "substantially vertical" mean that the direction of the length of the beam 110 is vertical, with a maximum margin of error of 20°. In other words, the direction of the beam 110 in its length may be substantially parallel to the main axis of the bust when the user is in the anatomical reference position. The terms "substantially parallel" mean that the direction of the length of the beam 110 is parallel to the main axis of the bust, with a maximum margin of error of 20°, preferably 10°. The anatomical reference position is the reference posture used by international convention in descriptive human anatomy. The beam 110 may also be adapted so that the large dimension of the beam 110 is parallel to a sagittal plane of a user of the exoskeleton and the small dimension of the beam 110 is perpendicular to the sagittal plane of the user of the exoskeleton.In one example, consistent with the previous example, beam 110 is a parallelepiped. Thus, in this example, beam 110 has six faces. [Fig.6] shows an example of a schematic representation of a beam 110. A first type of face of beam 110 is called a “large face.” dimension" in the present application and is denoted 111 in [Fig. 6]. A face of the large dimension has two edges 118 which are parallel to the large dimension of the cross-section of the beam and two edges 119 which are parallel to the length 115 of the beam. A second type of face of the beam 110 is called "face of the small dimension" in the present application and is denoted 112 in [Fig. 6]. A face of the small dimension has two edges 117 which are parallel to the small dimension of the cross-section of the beam and two edges 119 which are parallel to the length 115 of the beam. A third type of face is called "face of the side section" and is denoted 116 in [Fig. 6]. A face 116 of the side section has two edges 117 and two edges 118. The beam 110 has two faces 111 of the large dimension, two faces 112 of the small dimension and two faces 116 of the side section.The beam 110 is preferably a rectangular parallelepiped, also called a straight slab, and thus has six rectangular faces with all right angles.

[0024] In one example, compatible with the preceding examples, the beam 110 may have a first bending resistance, in the plane perpendicular to a plane comprising a face of the large dimension, of between 5 and 50 newtons. This first bending resistance of the beam 110 may be adapted so that the user can bend laterally easily. The terms “bend laterally” mean “perform a lateral flexion of the torso” or “perform an abduction of the torso. The term “easily” here means that the additional resistance linked to the dorsal structure to perform this lateral flexion movement of the torso is low, i.e. at most 50 newtons. The first bending resistance may be evaluated by a bending test in which the end 113 of the dorsal beam 110 is fixed and a force is applied perpendicular to the face 111 of the dorsal beam 110 of large dimension at the second end 114.The force required to cause the back beam 110 to bend 45 degrees in the plane perpendicular to the large face 111 is the value of the first bending resistance.

[0025] In an example, compatible with the previous examples, the dorsal beam 110 has a second flexural resistance, in a plane perpendicular to a plane comprising the small-dimension face, different from the first flexural resistance of the beam 110. The second flexural resistance can be evaluated by a flexure test in which the end 113 of the dorsal beam 110 is fixed and a force is applied perpendicularly to the face 112 of the small-dimension dorsal beam 110 at the second end 114. The force required to cause a flexure of the dorsal beam 110 in the plane perpendicular to the small-dimension face 112 is the value of the second flexural resistance. The flexure of the beam caused by the force may correspond to any measurable flexure, for example a flexure of an angle less than or equal to 2°.

[0026] This second bending strength of the beam 110 may be greater than the first bending strength of the beam 110. For example, the second bending strength of the beam 110 is 2 to 60 times greater than the first bending strength of the beam 110. Preferably, the second bending strength of the beam 110 is 5 to 10 times greater than the first bending strength of the beam 110. This second bending strength of the beam 110 may be between 50 and 300 newtons. This second bending strength of the beam 110 may be adapted to mechanically transmit a force applied, at a first fixed connection 120 of the backbone structure 110, to a second connection 130 of the backbone structure 110.The terms "mechanically transmit" mean in the present application that the movement originating from a force exerted at the first connection 120 of the backbone beam 110 is communicated to the second connection 130 of the backbone beam without being transformed, when the transmitted force is less than the second bending resistance, therefore less than a value between 50 and 300 newtons.

[0027] In one example, compatible with the previous examples, the length of the beam 110 is between 50 millimeters and 300 millimeters and preferably between 100 and 200 millimeters.

[0028] In one example, consistent with the preceding examples, the large dimension of the beam 110 is 5 to 20 times greater than the small dimension of the beam 110. Preferably, the large dimension of the beam 110 is 10 times greater than the small dimension of the beam 110. The large dimension therefore corresponds to the thickness of the beam in the large dimension. The small dimension therefore corresponds to the thickness of the beam in the small dimension. For example, the large dimension may have a dimension between 10 and 50 millimeters, preferably 30 millimeters. The small dimension of the beam 110 may have a dimension between 1 and 10 millimeters, preferably between 2 and 4 millimeters. The large dimension and the small dimension may obviously vary depending on the material used to manufacture the beam.

[0029] In one example, compatible with the previous examples, the back beam 110 is made of composite with: • carbon fibers, or • glass fibers, or • Kevlar fibers, or • flax fibers.

[0030] Preferably, the material used to manufacture the back beam 110 is flexible and / or has a low density. In addition, it is advantageous for the material to be ductile. The term “ductile” means in the present application “having a high breaking strength”. A carbon fiber composite material is particularly adapted. Furthermore, it is obvious that the dimensions of the beam 110 previously mentioned depend on the material used to manufacture the beam. Indeed, the bending strength of the material must in particular be taken into account so that the first and second bending strengths of the back beam 110 are adapted, for example included in the values ​​presented previously. For cost reasons, it is also possible to use a plastic-type material or a metal or a plant material such as wood or containing plant fibers.

[0031] The backbone structure 100 also comprises two links 120 and 130 located at each end of the beam 113 and 114. At the first end 113 of the beam 110, the first link 120 is fixed. The second link 130 is of the slide type. A slide type link makes it possible to guide a rectilinear translational movement along the main, or longitudinal, axis of the slide. The slide type link may comprise a part having a variable shape such as a cylinder or parallelepiped or rectangular parallelepiped shape or a rectangular prism. In one example, the backbone structure 100 further comprises other links. For example, the backbone structure 100 further comprises at least one other pivot type link, preferably between one and three other pivot type links.In this example, the at least one other pivot-type connection allows rotation around the length 115 of the beam and / or around an axis parallel to the main axis of the slide-type connection.

[0032] [Fig. 4] is an enlarged view of an example of the second connection 130 of the backbone structure 100. The second connection 130 is located at the second end 114 of the beam 110. The second connection 130 is, in this example, of the sliding pivot type. A sliding pivot type connection models a cylindrical contact of revolution. At the second connection 130, as illustrated in the example of [Fig. 4], the second connection 130 comprises a cylinder 133 of revolution, or cylindrical axis 133, and a component 132. A cylinder of revolution is the surface generated by the revolution, around a fixed axis, of a straight line parallel to the latter. It is common to characterize the dimensions of a cylinder by its radius and its height of a cylinder frustum. In the example illustrated in [Fig.4], all the points of contact between the cylinder 133, having a connecting axis 131 as its fixed axis, and the component 132 belong to the cylinder 133 of revolution.Thus, the contact normals between the cylinder 133 and the component 132 all meet the connecting axis 131 of the cylinder 133. In addition, the height of the cylinder 133 corresponds to the segment formed by the ends 134 and 135 of the cylinder 133. In the example illustrated in [Fig.4], the component 132 is a part having a cylinder-shaped opening, the diameter of which is greater than the diameter of the cylinder 133. It should be noted that the diameter of the opening of the component 132 is adapted so that the second connection is of the sliding pivot type. The sliding pivot type connection thus allows the user's torso to twist.

[0033] In one example, compatible with the previous examples, the second connection 130 is implemented by a plain or ball bearing coupled to a smooth ground cylinder 133. A plain bearing provides guidance in rotation and translation, along the cylinder 133, of the component 132 by sliding or rolling. When the bearing is a ball bearing, the guidance is provided by the rolling elements, i.e. the balls.

[0034] In one example, compatible with the previous examples, the cylinder 133 is a cylinder having a diameter between 5 and 30 millimeters, preferably between 10 and 15 millimeters. The diameter of the cylinder 133 is adapted so that the cylinder is sufficiently strong. The diameter of the cylinder is therefore adapted to avoid any breakage of the cylinder 133 during use of the back structure 100.

[0035] In one example, consistent with the preceding examples, the part enabling the connection 130 to be implemented, such as the cylinder 133, has a length of between 50 and 400, preferably between 100 and 250 millimeters. In addition, the sum of the length of the part enabling the connection 130 to be implemented and the length of the dorsal beam 110 may be adapted to correspond to the distance between the user's posterior iliac crests and the prominent vertebra, i.e. the base of the upper thoracic vertebrae. For example, the sum of the length of the part enabling the connection 130 to be implemented and the length of the dorsal beam 110 may be equal to 540 millimeters for a person measuring 182 centimeters.

[0036] In one example, consistent with the preceding examples, the second link 130 further comprises a rotational degree of freedom having an axis of rotation that is the main axis of the cylinder 133, also called the link axis 131. When the second link does not comprise a cylinder, the link axis 131 corresponds to the longitudinal or main axis of the second link 130. Thus, the rotational degree of freedom allows the component 132 to pivot around the cylinder 133. Thus, the rotational degree of freedom allows the component 132 of the second link 130 to form an angle, denoted 140 in FIGS. 2 and 4, between -45° and 45° with the cylinder 133 of the second link 130. The value 0° of the angle 140 corresponds to the relative orientation of the component 132 with respect to the cylinder 133 as illustrated in FIGS. 1 to 5.A positive value of the angle 140 may correspond to a clockwise rotation of the component 132 relative to the cylinder 133. In one example, consistent with the previous examples, the rotation axis of the second link 130 is offset between the link axis 131 and the main axis of the user's torso. The offset rotation axis may be parallel, with a maximum margin of error of 30°, to the link axis 131.

[0037] In one example, compatible with the previous examples, the second connection 130 is adapted so that the connection axis 131 further forms an angle 150 of between 120° and 180°, or equivalently of between 0° and 60°, with the length 115 of the beam 110 in a longitudinal section of the beam, i.e. in a plane comprising the length of the beam 110. The angle 150 is included in a plane parallel to the plane comprising the large face 111 of the beam 110. In other words, the second connection 130 is adapted so that the connection axis 131 also forms an angle 150 of between 120° and 180°, or equivalently of between 0° and 60°, with the length 115 of the beam 110. For example, the second connection can be adapted so that the connection axis 131 of the cylinder 133 is parallel to an axis defined by the user's pelvis and the base of the user's cervical vertebrae.

[0038] In one example, compatible with the previous examples, the dorsal structure 110 has a weight less than 2000 grams, and preferably less than 800 grams.

[0039] A second aspect of the invention relates to an exoskeleton for assisting walking and in particular for assisting mountain hiking. [Fig. 5] illustrates an example of an exoskeleton 200 according to the invention. The exoskeleton 200 notably comprises the dorsal structure 100 according to the invention. The exoskeleton 200 also comprises a lumbar belt 230 and a chest harness 240. The lumbar belt is adapted to surround a waist of the user. The waist is the part of the body located between the ribs, or thorax, and the hips of the user. The terms "surround a waist of the user" mean, for example, that the lumbar belt 230 securely surrounds the user at the level of the lumbar vertebrae, i.e. at the level of the user's lower back. The chest harness 240 is adapted to encircle the user's torso. The term "encircle" means that the harness can be attached to the user's torso, for example, using straps.The back structure 100 is fixedly connected to the lumbar belt 230 by the first connection 120. The harness 240 is connected to the back beam 110 by the second connection 130. For example, as illustrated in [Fig. 5], the harness 240 can be attached to the component 132 of the back structure 100.

[0040] In one example, consistent with the preceding examples, the chest harness 240 includes a rigid plate 250. The rigid plate 250 may be connected to the second connection 230. For example, as illustrated in [Fig. 5], the rigid plate 250 may be attached to the component 132 of the back structure 100. This rigid plate 250 may be in contact with an area of ​​the user's back located between the user's shoulder blades. For improved comfort, it is possible to add a flexible material to the face of the rigid plate in contact with the user's back.

[0041] The exoskeleton 200 also includes two hip actuators 210 and 220 attached to the lumbar belt 230. The right actuator 210 assists the flexion and extension movements of the user's right hip. The left actuator 220 assists the flexion and extension movements of the user's left hip. Each actuator generates a torque around the flexion / extension axis of a respective hip in order to assist the user's walking. Thus, each actuator transmits the assistance force to the thigh through a structure following the movements of the thigh. The dorsal structure 100 therefore makes it possible to transmit the reaction forces generated by the walking assistance provided by the actuators. The simplified resulting force is an almost normal force to the user's bust, forward or backward depending on the direction of assistance. Transmitting the force to the harness 240 rather than only to the lumbar belt makes it possible to increase the lever arm, and therefore to reduce the equivalent felt force. The walking assistance provided by the exoskeleton is therefore more comfortable than for an exoskeleton not including a harness.

[0042] Unless otherwise specified, the same element appearing in different figures has a single reference.

Claims

1.

2.

3.

4. Claims Back structure (100) for an exoskeleton for assisting a user in walking, comprising: - a beam (110) having a length (115) and a cross-section, the cross-section having a large dimension (118) and a small dimension (117), - a first fixed connection (120) with the exoskeleton located at a first end (113) of the beam (110), - a second connection (130) with the exoskeleton located at a second end (114) of the slide-type beam (110), and the dorsal structure (100) being characterized in that the large dimension of the beam is adapted to ensure efficient transmission of the forces generated by the actuators of the exoskeleton and the small dimension of the beam is adapted to allow lateral flexion mobility of the user's torso. Backbone structure according to claim 1 wherein the second connection (130) is of the sliding pivot type. Backbone structure according to claim 2 in which: - the second connection (130) comprises a degree of rotational freedom adapted to allow rotation around a connection axis (131) of the second connection (130) between -45° and 45°, and / or - the connecting axis (131) of the second connection (130) further forms an angle (150) of between 120° and 180° with the length (115) of the beam (110), the angle formed (150) being in a longitudinal section of the beam. A backbone structure according to any preceding claim wherein the beam (110) has: - a first bending resistance such that a first bending force having a magnitude between 5 and 50 newtons causes the backbone beam (110) to bend 45 degrees in the plane perpendicular to the large face (111) when the first bending force is applied perpendicular to the large face (111) at the second end (114) with the end (113) of the backbone beam (110) being fixed, and - a second bending resistance such that a second bending force having a magnitude between 50 and 300 newtons causes the backbone beam (110) to bend less than or equal to 2 degrees in the plane perpendicular to the small face (112) when the second bending force is applied perpendicular to the small face (112) at the second end (114) with the end (113) of the backbone beam (110) being fixed.

5. A backbone structure according to any preceding claim wherein the large dimension (118) of the beam (110) is between 10 and 50 millimeters and the small dimension (117) of the beam (110) is between 1 and 10 millimeters.

6. A backbone structure according to any preceding claim wherein the length (115) of the beam (110) is between 50 millimeters and 300 millimeters.

7. Backbone structure according to any one of the preceding claims in which the second connection (130) is formed by a smooth or ball bearing coupled to a smooth ground cylinder (133) of revolution.

8. Back structure according to the preceding claim in which a height of the smooth rectified cylinder (133) of revolution is between 50 and 400 millimeters.

9. Back structure for exoskeleton according to any one of the preceding claims in which the beam (110) is made of composite with: - carbon fibers, or - glass fibers, or - kevlar fibers, or - flax fibers.

10. Exoskeleton (200) for assisting a user in walking, comprising: - right (210) and left (220) actuators assisting a flexion and extension movement respectively of a right and left hip of the user, the actuators right and left (210, 220) being attached to a lumbar belt (230) adapted to surround a waist of the user, - A chest harness (240) adapted to surround a torso of the user, and - A back structure (100) according to any one of the preceding claims, the back structure (100) being linked to the lumbar belt (230) by the first connection (120) and to the chest harness (240) by the second connection (130).

11. The exoskeleton of claim 10 wherein the chest harness (240) comprises a rigid plate (250) connected to the second connection (230).

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