Improved Disturbance Rejection in Repetitive-Control Systems: Phase-Compensated Equivalent-Input-Disturbance Approach

This article presents a phase-compensated equivalent-input-disturbance approach-based repetitive-control system that aims to precisely track periodic signals and effectively suppress aperiodic signals. A generalized modified repetitive control, which completely separates control and learning through two gains, is constructed to achieve independent control-learning regulation without using a 2-D model. On the other hand, the low-pass filter in the equivalent-input-disturbance estimator introduces a phase offset while ensuring causality. Such a phase delay reduces the suppression accuracy of time-varying disturbances. A phase compensator is added to accurately compensate for the phase delay through detailed analysis, thus improving the disturbance-rejection performance. Finally, theoretical analysis and experimental results demonstrate the effectiveness and superiority of the method.