Robust output tracking control for the systems with uncertainties

A new robust tracking control is proposed for the minimum phase dynamical systems with parameter uncertainties and unmatched disturbance, where only the input-output measurement of the system is employed. The system parameters may vary slightly around their corresponding nominal values. The disturbance is assumed to be bounded. However, the upper and lower bounds are unknown. First, the frame of the control law is presented. Then, a special bounded signal is generated by the disturbance and the model uncertainties are estimated by a new non-linear method, where the upper and lower bounds of the special signal are adaptively updated online. Finally, the robust tracking control is synthesized by using the estimate of the special signal. The output tracking error can be made as small as necessary by choosing the design parameters. The attraction of the proposed method lies in its robustness to uncertainties and its ease of implementation. Example and simulation results are presented to show the effectiveness of the proposed algorithm.