Improving Track Performance by Combining Padé-Approximation-Based Preview Repetitive Control and Equivalent-Input-Disturbance

In this study, the problem of Padé-approximation-based optimal preview repetitive control (POPRC) with equivalent-input-disturbance (EID) for a class of continuous-time uncertain systems is proposed. Firstly, a delay-free state-space representation of the modified repetitive control (MRC) system is constructed using the Padé-approximation method. Then, an augmented dynamic system that incorporates the output of MRC system is established. Subsequently, the POPRC problem transformed into a linear quadratic regulation problem of an augmented dynamic system by introducing a quadratic performance index. To ensure the robustness of the closed-loop system in the presence of external disturbances, the standard EID technique is cooperated with the POPRC law by applying the Separation Theorem. Furthermore, the stability of the overall control system is proved by using small-gain theorem. Compared with the existing result, a simplified POPRC law with EID is obtained for the original system. Finally, simulation results are presented to illustrate the effectiveness and robustness of the controller.