A Performance Enhancement Scheme for Robust Repetitive Control System

This paper presents a method for enhancing the performance of a digital repetitive control system. The performance at the fundamental frequency and its harmonics of repetitive exogenous signals is improved by applying a modified low-pass qz,z−1 filter structure in the repetitive signal generator of the internal model. Stability and robust performance is achieved through μ-synthesis. The modified low-pass filter is motivated by the attempt to reduce the sensitivity function by squaring it. The magnitude of the sensitivity function is substantially reduced at the periodic reference frequencies since the value is already much less than unity. The proposed approach is demonstrated by its implementation on an electrohydraulic actuator for tracking periodic cam-like profiles.