Robust controller with a supervisor implemented on a flexible joint robot

In this paper a controller for flexible joint robots (FJR) in presence of actuator saturation is proposed, its robust stability is analyzed, and it is implemented on a laboratory FJR. This controller consists of a composite structure, with a PD controller on the fast dynamics and a PID controller on slow dynamics. The need of powerful actuator is released through decrease of fast controller bandwidth at critical occasions. This is done by means of a fuzzy logic supervisory loop. The stability analysis of the overall system is then analyzed by Lyapunov theory. It is proven that UUB stability of the overall system in presence of uncertainties is guaranteed, provided that the PD and the PID gains are tuned to satisfy certain conditions. Experimental studies are forwarded to verify the effectiveness and the performance of the proposed controller