DEVICE FOR CONTROLLING A ROBOTIC SYSTEM FOR ASSISTING THE MOBILITY OF A USER

Abstract

The present invention concerns a device for controlling a robotic system for assisting the mobility of a user, said robotic system comprising at least one active mobility assistance element capable of assisting a given mobility action of the user, characterized in that the device comprises a detection system capable of detecting a compensatory movement of the user associated with the mobility action, said compensatory movement being a movement made by a user who is disabled, or able-bodied but locally and/or temporarily constrained, in order to perform at least part of the mobility action, and which at least partially substitutes the normal movement an unconstrained, able-bodied user would make in order to perform this mobility action, and a control system capable of controlling the at least one active element when the compensatory movement is detected.

Claims

1. A device for controlling a robotic system for assisting the mobility of a user, said robotic system comprising at least one active mobility assistance element capable of assisting a given mobility action of the user, characterized in that the device comprises a detection system capable of detecting a compensatory movement of the user associated with the mobility action, said compensatory movement being a movement made by a user who is disabled, or able-bodied but locally and/or temporarily constrained, in order to perform at least part of the mobility action, and which at least partially substitutes the normal movement an unconstrained, able-bodied user would make in order to perform this mobility action, and a control system capable of controlling the at least one active element when the compensatory movement is detected.

2. The device according to claim 1, characterized in that the active element is a robotic arm prosthesis or an assistance arm exoskeleton.

3. The device according to claim 2, characterized in that the mobility action is to reach a target, and in that the compensatory movement is an inclination of the user's torso.

4. The device according to claim 1, characterized in that the detection system is configured to detect a difference between a reference position (Θr) and a position (Θc) of the user, and to detect a compensatory movement when said deviation reaches a predetermined deviation.

5. The device according to claim 1, characterized in that said at least one active mobility assistance element is an active element intended to be secured to the user.

6. The device according to claim 5, characterized in that said at least one active mobility assistance element is a motorized joint.

7. The device according to claim 1, characterized in that the active mobility assistance element is an active element external to the user.

8. The device according to claim 7, characterized in that the active mobility assistance element is an active element for controlling a movement of a target of the user.

9. The device according to claim 1, characterized in that the control system is further configured to induce a correction of the compensatory movement.

10. An assembly for assisting the mobility of a user, characterized in that it comprises a device according to claim 1 and a robotic system controlled by said device.

11. A method of controlling a robotic system for assisting the mobility of a user, characterized in that it implements a device according to claim 1.

12. The method according to claim 11, characterized in that it comprises the steps of: determining a mobility action of a user, associating said mobility action with a compensatory movement of the user, when said compensatory movement is detected, controlling at least said active mobility assistance element.

Description

[0032] Other advantages and features of the present invention will become clear from the following description, given by way of non-limiting example, and made with reference to the appended figures:

[0033] FIG. 1 is a block diagram illustrating the overall operation of a device for controlling a robotic mobility assistance system according to the invention,

[0034] FIG. 2 to 4 schematically illustrate different positions of a user performing a mobility action using the control device according to the invention,

[0035] FIG. 5 is a graph illustrating the progression over time of the inclination angle of the trunk and the flexion angle of the elbow of the user in FIG. 2 to 4, according to a first embodiment,

[0036] FIG. 6 is a graph illustrating the progression over time of the flexion angle of the trunk and the flexion angle of the elbow of the user in FIG. 2 to 4, according to a second embodiment, and

[0037] FIG. 7 is a graph illustrating different simulations of the progression over time of the flexion angle of the trunk and the flexion angle of the elbow in a user performing a pointing gesture and in different cases: natural gesture, gesture with blocked elbow (resulting in significant compensation of the trunk), and gesture with the proposed control mode (here automatically controlling the movement of the elbow according to the compensations of the trunk).

[0038] The device according to the invention makes it possible to control a robotic system for assisting mobility, and in particular for assisting the mobility of the upper limbs, for example a prosthesis or an exoskeleton of an upper limb. It uses as a control input the compensatory movements naturally implemented by the central nervous system (CNS) to perform functional tasks, such as, in the example which will be described, when the mobility of the upper limb(s) of the user is reduced.

[0039] These compensations, recorded by different sensors, allow the system to identify the movement, or motor intention, that the user wishes to perform and to deduce from it an action strategy of the robotic system, due in particular to an inverse kinematic model, for assisting the user in carrying out his task. The movement is then carried out by the robotic joint(s), while the user naturally and instinctively returns to a neutral posture, without postural compensation.

[0040] This is illustrated in FIG. 1. Θr denotes the reference position of the user's body, without compensation, while Θc denotes the current position of the body and 3′ denotes the matrix of angular speeds of the robotic joints.

[0041] In the example which will be described in reference to FIG. 2 to 7, the invention uses a control algorithm which makes it possible to assist the mobility of an upper limb. The algorithm allows intuitive control of the device because it is based on the use of strategies naturally implemented by the central nervous system to compensate for a reduction in said mobility. In a simplified version, which is the control of a single joint, that of the elbow, the device according to the invention was tested on ten healthy users whose movement of the elbow was driven by a robotic joint of the exoskeleton type. The users wore sensors on the trunk and on the arm. The experiment consisted of hitting a set of six targets, located at different distances and at different heights. All the users succeeded in the mobility action, correctly controlling the joint through the implementation of compensatory strategies, even though no explanation of the operation of the control of the robotic tool had been given to them.

[0042] Thus, as illustrated in FIG. 2, a user 1 is initially in a reference position, the trunk being arranged vertically. The reference position may be generally defined as being a comfortable position, without postural compensation, that the user would naturally adopt to perform the mobility action if he had control of all his joints. However, it is conceivable that the reference position of the trunk is a leaning position because certain gestures require the user to be naturally leaning. A non-static definition of the reference position may be added to the control law.

[0043] In the mobility action consisting in reaching a target at a distance from the user, the user whose arm is disabled will naturally tilt his trunk 5 forward to compensate for the disability of his arm. Thus, in the case where the mobility action is to reach a distant target 4, the associated compensatory movement is the forward inclination of the trunk 5. Alternatively, one could choose as the associated compensatory movement a movement of the shoulder or the shoulder blades.

[0044] When the user 1 leans forward (FIG. 3), sensors determine the inclination of the trunk 5 relative to the reference position in FIG. 2. It is possible to use sensors arranged on the trunk 5 of the user 1, such as deformable elastic sensors, or optical sensors.

[0045] When the inclination of the trunk 5 reaches a predetermined value, the compensatory movement is detected, and the device 2 will control the active mobility assistance element, which in this example is a prosthetic elbow joint 3. When the compensatory movement is detected, the device 2 commands the prosthetic elbow to open, which will allow the user 1 to reach the target 4 (FIG. 4).

[0046] In this example, a two-dimensional inverse kinematic model is used for the elbow joint. However, a three-dimensional model may be considered more generally, with for example at least two motorized joints.

[0047] The invention is distinguished by its natural control law, which only uses the strategies already set up naturally by the central nervous system, and therefore requires very little learning. The user does not have to think about what to do. In addition, the control is carried out in the space of the mobility action (space of the task). What matters is not to move a joint, but to perform a given gesture, to position the hand in a given place. The output of the control law is not the movement of a single joint, but rather the coordinated movement of all the controlled joints necessary to perform the desired gesture, combined with the joints that the user always controls naturally (functional joint, stump, etc.). The joints are not controlled individually and sequentially, but simultaneously, as in a natural gesture. In the task of grasping an object, for example, no person without an amputated limb reflects on the individual position of his joints. The person is focused on the object to be reached, and therefore on the position of his hand, and he controls his arm in the space of the task.

[0048] The invention therefore reduces the learning time and the cognitive load. Its implementation is simple and fast because there is no training phase for the algorithm. The small number as well as the small size of the motion sensors allow for a use without constraint, in an open and home environment.

[0049] FIG. 5 illustrates the progression over time of the inclination angle of the trunk Θ.sub.T and of the flexion angle of the elbow β of the user when the mobility action is the grasping of an object.

[0050] At the start of the process, the user's trunk is in its reference position Θ.sub.0. The user, wishing to reach the targeted object with his hand, will initiate a compensatory movement which is tilting the trunk forward. When the inclination of the trunk reaches a predetermined value Θ.sub.1, characteristic of the detection of the compensatory movement, the control system of the device commands the prosthetic elbow joint to open. The elbow thus opens progressively, from a flexion angle β.sub.0 to a flexion angle β.sub.1, which brings the hand closer to the object to be grasped.

[0051] FIG. 6 illustrates the progression over time of the inclination angle of the trunk OT and of the flexion angle of the elbow β of the user when the mobility action is the grasping of two objects.

[0052] Grasping the first object begins in the same way as in the embodiment shown in FIG. 5. From a reference position Θ.sub.0 of the user's trunk, said user initiates a first forward compensatory movement of the trunk until the trunk is tilted to a predetermined value Θ.sub.1, characteristic of the detection of the first compensatory movement. The device's control system commands the prosthetic elbow joint to open from a flexion angle β.sub.0 to a flexion angle β.sub.1, which brings the hand closer to the first object to be grasped.

[0053] Once the first object has been reached, the user then wishes to grasp a second object, which is closer to him than the first object. The user will then initiate a second compensatory movement, which is to tilt the trunk backwards, so as to bring his hand closer to the second object. When the inclination of the trunk reaches a predetermined value Θ.sub.2, characteristic of the detection of the second compensatory movement, the control system of the device commands the prosthetic elbow joint to close. The elbow thus closes progressively, from the flexion angle β.sub.1 to a flexion angle β.sub.2 allowing the second object to be reached.

[0054] FIG. 7 illustrates different simulations of the progression over time of the inclination angle of the trunk and of the flexion angle of the elbow, the mobility action being to reach a target in space. Three configurations were considered: a user whose elbow joint is functional (“natural” curves), a user whose elbow joint is non-functional, without the assistance of the device (“blocked elbow” curves), and a user whose elbow joint is non-functional with the assistance of the device (“compensation detection” curves).

[0055] The simulations show that the behavior of the disabled user using the assistance device according to the invention, in terms of inclination of the trunk and flexion of the elbow, approaches the behavior of an able-bodied user.

[0056] The control system of the device according to the invention may also be seen as a simple approach to correcting the compensatory movement. In the example of grasping an object illustrated in FIG. 5, it may thus be considered that an active robotic element is in fact controlled so as to decrease the inclination of the torso when the compensatory movement has been detected: the opening of the elbow is actually increased so as to compensate for the decrease in the inclination of the torso.

[0057] In one embodiment of the invention, the device may not control a movement of the user toward the object to be reached, as just described, by moving the hand toward the object by opening or closing the elbow, but rather may control a movement of the object to be reached toward the user. In the example of grasping an object illustrated in FIG. 5, it is thus possible to envisage that an active robotic element integral with the object is controlled so as to bring the object closer to the hand of the user when the compensatory movement is detected. Naturally, this embodiment may be combined with the embodiment in which the user is controlled so as to move toward the object to be reached.