Redundant input guaranteed cost non-fragile tracking control for omnidirectional rehabilitative training walker

Abstract

In this study, the problem of guaranteed cost non-fragile tracking control on the omnidirectional rehabilitative training walker is examined. The nonlinear redundant input method is proposed when one wheel actuator fault occurs. The aim of the study is to design an asymptotically stable controller that can guarantee the safety of the user and ensure tracking on a training path planned by a physical therapist. The guaranteed cost control and the asymptotically zero state detectable concept of the walker are presented, and the model of redundant degree is constructed. The cost performance index is defined to restrain initial oversize input forces. On the grounds of LMI, a controller with gain variations that can satisfy asymptotic stability is obtained using a common Lyapunov function for admissible uncertainties resulting from an actuator fault. Simulation results confirm the effectiveness of the proposed method and verify that the walker can provide safe sequential motion when one wheel actuator is at fault.