Modeling and control design of a rehabilitation exoskeleton on actuated wheels

A novel architecture based on the use of two independently actuated wheels is proposed for a rehabilitation exoskeleton with swinging legs. First, the equations of motion of the exoskeleton are derived via Euler-Lagrange principles yielding, by the structure of the mechanics, a purely continuous-time model without impacts. To impose a gait-like motion suitable for rehabilitation purposes, a two-step control scheme is envisioned: a reference generator unit is combined with a low-level feedback control for the individual wheels. For the latter, the dynamical model is employed for emulating, initially via simulation, a Reinforcement Learning approach to compute the optimal scheduling of different (stabilizing) PID controllers, hence paving the way for the future extension to a purely model-free framework for the actual prototype