Tracking control for an omnidirectional rehabilitative training walker with safety velocity performance

In this study, a new nonlinear trajectory tracking method with velocity constraints performance is proposed for an omnidirectional rehabilitative training walker. The aim is to guarantee the rehabilitee can complete rehabilitation training under the safety velocity. According to Lyapunov theory, the safety velocity controller can be designed to maintain stability in terms of solutions of linear matrix inequalities. The concept of safety velocity is given and the sufficient condition for the existence of such a controller with safety velocity constraints performance is derived. As an application, simulation results confirm the effectiveness of the proposed method and verify that the walker can provide safe training velocity.