Compensation for Input Nonlinearities in Repetitive Control Systems Based on Improved Equivalent-Input-Disturbance Approach

The equivalent-input-disturbance (EID) approach is used to deal with the problem of tracking period signals for a plant with input actuator nonlinearities in a repetitive control system. First, an EID estimator is constructed by taking the full advantage of an extended state observer (ESO), the design of the ESO is explained. Next, an EID estimate, which represents the synthetic effect of the nonlinearities, is incorporated into a repetitive control law to compensate for the effect caused by the nonlinearities. This method does not require any prior information about the nonlinearities. It guarantees perfect tracking for periodic reference input and satisfactory compensation for input nonlinearities at the same time. Finally, simulation and experimental results show the effectiveness of the method.