US-12622836-B2 - Methods for generating a trajectory of an exoskeleton and for setting the exoskeleton in motion

US12622836B2US 12622836 B2US12622836 B2US 12622836B2US-12622836-B2

Abstract

The present invention relates to a method for generating a trajectory of an exoskeleton ( 1 ) provided with two legs each having a foot, the method comprising the implementation by data-processing means ( 11 a ) of a server ( 10 a ), of steps of: (a) obtaining at least one n-tuple of gait parameters defining a given gait of the exoskeleton ( 1 ); (b) generating at least one periodic elementary trajectory of the exoskeleton ( 1 ) for said n-tuple of gait parameters, such that said periodic elementary trajectory comprises in sequence a first trajectory portion and a second trajectory portion, such that in the first trajectory portion each foot performs a pure rotation, and in the second portion only one foot performs a translation.

Inventors

Stanislas Brossette
Guilhem BOERIS

Assignees

WANDERCRAFT

Dates

Publication Date: 20260512
Application Date: 20210210
Priority Date: 20200210

Claims (12)

1 . A method for generating a trajectory of an exoskeleton provided with two legs each having a foot, the method comprising the implementation by data-processing means of a server, of steps of: (a) obtaining at least one n-tuple of gait parameters defining a given gait of the exoskeleton; (b) generating at least one periodic elementary trajectory of the exoskeleton for said n-tuple of gait parameters, while applying conditions such that said periodic elementary trajectory comprises in sequence a first trajectory portion and a second trajectory portion, such that: in the first trajectory portion each foot performs a pure rotation, and in the second trajectory portion only one foot performs a translation starting with the foot that performs the translation being in contact with the ground only at a toe tip thereof and ending with the foot that performs the translation being in contact with the ground only at a heel thereof, while the foot that does not perform the translation remains immobile flat on the ground all along the second trajectory portion.
2 . The method according to claim 1 , wherein the conditions are such that said elementary periodic trajectory cyclically repeats the sequence of said first trajectory portion then second trajectory portion.
3 . The method according to claim 1 , wherein the conditions are such that, in the second trajectory portion, the foot that performs the translation is an initially rear foot of the exoskeleton that is positioned rear of an initially front foot of the exoskeleton at a beginning of the at least one periodic elementary trajectory.
4 . The method according to claim 1 , wherein the conditions are such that at the end of the first trajectory portion an initially front foot of the exoskeleton that is positioned in front of an initially rear foot of the exoskeleton at a beginning of the at least one periodic elementary trajectory is flat on the ground.
5 . The method according to claim 1 , wherein the step (b) is implemented by using at least one neural network.
6 . The method according to claim 1 , said exoskeleton receiving a human operator, the step (a) comprising the determining of a sequence of n-tuples of gait parameters of the exoskeleton desired by said operator.
7 . The method according to claim 6 , wherein the generated trajectory of the exoskeleton comprises for each n-tuple of said sequence a new elementary periodic trajectory and a transition to this new elementary periodic trajectory.
8 . The method according to claim 1 , wherein the step (b) is implemented by using optimization tools capable of generating the at least one periodic elementary trajectory according to said conditions and n-tuple of gait parameters.
9 . A method for setting an exoskeleton in motion having a plurality of degrees of freedom of which at least one degree of freedom actuated by an actuator controlled by data-processing means comprising a step (c) of executing by the data-processing means of the exoskeleton of a trajectory of the exoskeleton, in such a way as to cause said exoskeleton ( 1 ) to walk, said trajectory of the exoskeleton being generated by the implementation of the steps of: (a) obtaining at least one n-tuple of gait parameters defining a given gait of the exoskeleton; (b) generating at least one periodic elementary trajectory of the exoskeleton for said n-tuple of gait parameters, while applying conditions such that said periodic elementary trajectory comprises in sequence a first trajectory portion and a second trajectory portion, such that: in the first trajectory portion each foot performs a pure rotation, and in the second trajectory portion only one foot performs a translation starting with the foot that performs the translation being in contact with the ground only at a toe tip thereof and ending with the foot that performs the translation being in contact with the ground only at a heel thereof, while the foot that does not perform the translation remains immobile flat on the ground all along the second trajectory portion.
10 . A system comprising a first server and an exoskeleton each comprising data-processing means, characterised in that said data-processing means are configured to implement a method for generating a trajectory of an exoskeleton provided with two legs each having a foot, the method comprising the implementation by data-processing means of a server, of steps of: (a) obtaining at least one n-tuple of gait parameters defining a given gait of the exoskeleton; (b) generating at least one periodic elementary trajectory of the exoskeleton for said n-tuple of gait parameters, while applying conditions such that said periodic elementary trajectory comprises in sequence a first trajectory portion and a second trajectory portion, such that: in the first trajectory portion each foot performs a pure rotation, and in the second trajectory portion only one foot performs a translation starting with the foot that performs the translation being in contact with the ground only at a toe tip thereof and ending with the foot that performs the translation being in contact with the ground only at a heel thereof, while the foot that does not perform the translation remains immobile flat on the ground all along the second trajectory portion.
11 . A computer program product comprising code instructions for the execution of a method for generating a trajectory of an exoskeleton provided with two legs each having a foot, the method comprising the implementation by data-processing means of a server, of steps of: (a) obtaining at least one n-tuple of gait parameters defining a given gait of the exoskeleton; (b) generating at least one periodic elementary trajectory of the exoskeleton for said n-tuple of gait parameters, while applying conditions such that said periodic elementary trajectory comprises in sequence a first trajectory portion and a second trajectory portion, such that: in the first trajectory portion each foot performs a pure rotation, and in the second trajectory portion only one foot performs a translation starting with the foot that performs the translation being in contact with the ground only at a toe tip thereof and ending with the foot that performs the translation being in contact with the ground only at a heel thereof, while the foot that does not perform the translation remains immobile flat on the ground all along the second trajectory portion.
12 . A means of storage that can be read by a piece of computer equipment whereon a computer program product is recorded comprising code instructions for the execution of a method for generating a trajectory of an exoskeleton provided with two legs each having a foot, the method comprising the implementation by data-processing means of a server, of steps of: (a) obtaining at least one n-tuple of gait parameters defining a given gait of the exoskeleton; (b) generating at least one periodic elementary trajectory of the exoskeleton for said n-tuple of gait parameters, while applying conditions such that said periodic elementary trajectory comprises in sequence a first trajectory portion and a second trajectory portion, such that: in the first trajectory portion each foot performs a pure rotation, and in the second trajectory portion only one foot performs a translation starting with the foot that performs the translation being in contact with the ground only at a toe tip thereof and ending with the foot that performs the translation being in contact with the ground only at a heel thereof, while the foot that does not perform the translation remains immobile flat on the ground all along the second trajectory portion.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is the 35 U.S.C. § 371 national stage application of PCT Application No. PCT/FR2021/050242, filed Feb. 10, 2021, which application claims the benefit of French Application No. FR 2001317 filed Feb. 10, 2020, both of which are hereby incorporated by reference herein in their entireties. TECHNICAL FIELD GENERAL The present invention relates to the field of robots of the exoskeleton type. More precisely, it relates to a method for generating a trajectory of an exoskeleton and a method for setting the exoskeleton in motion. STATE OF THE ART Recently, for persons with substantial mobility problems such as paraplegics, assisted devices for walking called exoskeletons have appeared, which are external robotic devices that the operator (the human user) “puts on” thanks to a system of fasteners that links the movements of the exoskeleton with their own movements. Exoskeletons of lower limbs have several articulations, generally at least at the knees and hips, to reproduce the gait movement. Actuators make it possible to move these articulations, which in turn cause the operator to move. An interface system allows the operator to give orders to the exoskeleton, and a command system transforms these orders into commands for the actuators. Sensors also supplement the device. These exoskeletons constitute progress with respect to wheelchairs, because they allow the operators to stand up and walk. Exoskeletons are no longer limited by wheels and can theoretically move about in most non-flat environments: wheels, contrary to legs, do not make it possible to cross substantial obstacles such as steps, stairs, obstacles with an excessive height, etc. However, in their use, none of these exoskeletons performs an autonomous human gait, i.e. stable and viable over a large variety of terrains, that is anthropomorphic and unassisted. In most cases, these limitations are materialised by the impossibility for the device to manage the balance or the direction of gait itself. These two tasks are then generally transferred to the operator, who performs them thanks to crutches, as proposed for example in U.S. Pat. No. 7,153,242 of Rewalk, or in application US2016038371 of Ekso-Bionics. Patent EP2231096 of Rex-Bionics describes the only exoskeleton that can be used without external aid for a person that is incapable of assuring their own stability. The control principle, described in paragraph [0122], clearly explains the need to transfer the centre of pressure (the physical point at which the moment of the reaction forces exerted by the ground on the system is zero) from a portion of the support polygon (the convex envelope of the contact points with the ground) to another portion of the support polygon. This limitation imposes an extremely slow gait (a few metres per minute, while a normal gait exceeds 2 km/h which is 33 metres per minute) with short steps (less than 30 cm, while a normal stride ranges from 50 to 80 cm), during which the support foot is constantly in flat contact with the ground. The type of environment that can be accessed is therefore limited, since uneven terrains are excluded de facto. Likewise, the slightest obstacle such as a stone, a small object, generates a risk of unbalancing the system if it places its foot on it at a given moment, and finally causes it to fall. In opposition, “natural” human gait is characterised by a sequence of phases during which the feet can be flat on the ground, in the air, or in the process of rolling on the ground, as can be seen in FIG. 1. This capacity to roll the foot is essential for the gait because it makes it possible to take greater steps and allows for stability over a large variety of terrains. However the so-called first-generation exoskeletons described hereinabove do not have an actuated foot or keep the support foot on the ground. Performing this roll is indeed complex for bipedal humanoid robots or robotic devices. Even if a foot structure with a break as proposed in application WO2015140353 is provided, when the centre of pressure reaches the limit of the support polygon, the system begins to roll around this point, and is therefore no longer in static equilibrium. In the case of the gait, the roll of the foot involves a partial loss of contact with the ground at the support foot, with several consequences: the support polygon (the sustentation surface) is reduced, potentially to a point, making it difficult if not impossible to maintain the centre of pressure inside the support polygon;the system is in a situation of underactuation, i.e. it can no longer act over all its degrees of freedom. All the movements are then no longer possible. In such a situation, the conventional formalisms of flat foot walking such as described in the document Kajita S., K. F. (2003). Biped Walking pattern generation by using preview control of Zero-Moment Point. ICRA, (pp. 1620-1626), or the principle described in patent Rex-Bion