A filtered repetitive controller for a class of nonlinear systems

In this note, a filtered repetitive controller (FRC) is designed to compensate for periodic disturbances in a class of nonlinear systems. First, a new model of periodic disturbances is proposed. By this model, the FRC is designed and the resulting closed-loop error dynamics are analyzed with the help of a Lyapunov-Krasovskii functional. Finally the method is applied to periodic disturbance rejection in a class of robotic manipulators. Compared with repetitive controllers, the FRC provides the flexibility to choose filter parameters to achieve a tradeoff between tracking performance and stability. More importantly, FRC can deal with small input delay while the corresponding RC cannot.