High gain adaptive output feedback control for time-varying nonlinear systems with higher order relative degree

This paper deals with a controller design problem for time-varying nonlinear systems with higher order relative degree. A robust adaptive tracking control for time-varying nonlinear systems with stable zero dynamics is proposed based on the high-gain adaptive output feedback and backstepping strategies. The proposed method utilizes filtered signals of the control input to construct the robust adaptive controller instead of state variables. Therefore, the proposed method is useful in the case where only the output signal is available.