Design of a robust controller using only output feedback to solve the servomechanism problem

The design of a robust controller using only output feedback to solve the servomechanism problem is considered. A PI control algorithm and a sliding-mode control design are combined to alleviate system uncertainties and to solve the output regulation problem. A reduced-order observer for the transformation matrix is proposed to estimate the system states, and a control law is designed with respect to the estimated signals. Asymptotic regulation is also satisfied by using the estimated states in the controller. A numerical example is presented to demonstrate the applicability of the proposed control scheme.