Adaptive tracking control for stochastic mechanical systems with actuator nonlinearities

In this paper, output tracking control problem is investigated for a class of uncertain nonlinear random mechanical systems subjected to unknown actuator nonlinearities. Two common kinds of actuator nonlinearities, namely, Bouc-Wen hysteresis and dead-zone, are considered in a unified framework, such that the designed adaptive control law is robust to the mentioned actuator nonlinearities (hysteresis and dead-zone). Different from some existing controller design approaches for nonlinear systems with actuator nonlinearities, the usual priori knowledge on the known compact set for system uncertain parameters has been eliminated with the proposed control method. The proposed control law can ensure that the system output tracking error eventually converges to an arbitrarily small neighborhood of zero in the sense of mean square by turning controller gains. Simulation studies are performed to demonstrate the effectiveness of the proposed controller design approach.