Balance control for an underactuated leg exoskeleton based on capture point concept and human balance strategies

This paper presents a balance control for a powered lower limbs exoskeleton based on the instantaneous capture point concept and human balance strategies. Our goal is to implement it on the exoskeleton EMY-Balance (CEA-LIST). The control is inspired from biomechanic studies and aims at assisting a healthy person while preserving his comfort and his safety to the maximum. We first present briefly how the machine can balance itself according to external perturbations which can come from the user, and how it can imitate human balance strategies. Then, we present how we compute joint torques for the specific actuation of EMY-Balance. We suppose in this study, that the user and the exoskleton share the same control : (1) the proposed control assists stand leg(s) in order to facilitate the balance recovery, (2) the user is supposed to compensate efforts to overcome actuation issues.