Robust time-varying output tracking control in the presence of actuator saturation

This paper considers the problem of output tracking of a time-varying reference signal for a class of uncertain systems in the presence of actuator saturation. To achieve this capability, a new controller is proposed by robustifying the generalized composite nonlinear feedback control method with the integral sliding mode controller. Since the proposed controller may be saturated, a precise analysis is done to show its robust performance despite the presence of actuator saturation and model uncertainties. For this purpose, a theorem is given and proved that guarantees the robust output tracking via the proposed control law for three different cases of the saturation function and it is shown that even if the control signal is saturated, the proposed controller achieves output tracking of the time-varying reference signal. Also, in order to show the applicability of the proposed controller, it is applied on two practical systems, the XY-table and inertia wheel inverted pendulum. Computer simulations verify the theoretical results and also display the effective performance of the proposed controller.