Robust Tracking Control of a Prosthesis Test Robot

This paper develops a passivity-based robust motion controller for a robot used in pros-thetic leg performance studies. The mathematical model of the robot and passive prosthe-sis corresponds to a three degree-of-freedom, 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 develop-ment. 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 passivity-based con-troller suitable for an underactuated system and compare it with a simple independent-joint sliding mode controller (IJ-SMC). This paper describes the mathematical model and nominal parameters, derives the passivity-based controller using Lyapunov techniques and reports success in real-time implementation of both controllers, whose advantages and drawbacks are compared. [DOI: 10.1115/1.4026342]