Robust Tracking Control of a Prosthesis Test Robot

Abstract

This paper develops a passivitybased robust motion controller for a robot used in prosthetic leg performance studies. The mathematical model of the robot and passive prosthesis corresponds to a three degreeoffreedom, underactuated rigid manipulator. A form of robotic testing of prostheses involves tracking reference trajectories obtained from human gait studies. The robot presented in this paper emulates hip vertical displacement and thigh swing, and we consider a prosthesis with a passive knee for control development. The control objectives are to track commanded hip displacements and thigh angles accurately, even in the presence of parametric uncertainties and large disturbance forces arising from ground contact during the stance phase. We develop a passivitybased controller suitable for an underactuated system and compare it with a simple independentjoint sliding mode controller (IJSMC). This paper describes the mathematical model and nominal parameters, derives the passivitybased controller using Lyapunov techniques and reports success in realtime implementation of both controllers, whose advantages and drawbacks are compared.