Repetitive controller for compensation of periodic signal

Abstract

"A repetitive controller scheme with positive feedback and feedforward introduces infinitely many poles on the imaginary axis located at the resonant peaks. The feedforward introduces zeros, which produce notches located in between two consecutive resonant peaks. The latter has the advantage of making the controller more selective, in the sense that; the original overlapping (appearing at the valleys in a simple positive feedback repetitive controller) or interaction between consecutive resonant peaks is removed by the notches. This would allow, in principle, peaks of higher gains and slightly wider bandwidth, avoiding, at the same time, the excitation of harmonics located in between two consecutive peaks. The repetitive controller includes a simple Low Pass Filter (LPF).; This modification restricts the bandwidth of the controller and at the same time reinforces stability when the controller is inserted in the closed-loop system."