Fast replanning of a lower-limb exoskeleton trajectories for rehabilitation

Maxime Brunet (1, 2) , Marine Pétriaux (1) , Florent Di Meglio (2) , Nicolas Petit (2)

1 Wandercraft
2 CAS - Centre Automatique et Systèmes

The paper addresses the rehabilitation of disabled patients using a lower-limb fully-actuated exoskeleton. We propose a novel numerical method to replan the current step without jeopardizing stability. Stability is evaluated in the light of a simple linear time-invariant surrogate model. The method's core is the analysis of an input-constrained optimal control problem with state specified at an unspecified terminal time. A detailed study of the extremals given by Pontryagin Maximum Principle is sufficient to characterize its feasibility. This allows a fast replanning strategy. The efficiency of the numerical algorithm (resolution time below 1 ms) yields responsiveness to the patient's request. Realistic simulations on a full-body model of the patient-exoskeleton system stress that cases of practical interest for physiotherapists are well-addressed.

Domaines: Automatique / Robotique; Automatique; Optimisation et contrôle [math.OC]

Maxime Brunet, Marine Pétriaux, Florent Di Meglio, Nicolas Petit. Fast replanning of a lower-limb exoskeleton trajectories for rehabilitation. Conference on Decision and Control, 2022 IEEE 61st Conference on Decision and Control (CDC), Dec 2022, Cancun, Mexico. ⟨10.1109/CDC51059.2022.9992460⟩. ⟨hal-03772920⟩