Analog circuits to implement repetitive controllers for tracking and disturbance rejection of periodic signals

In this paper, simple analog circuits to implement a repetitive control scheme are discussed. The repetitive control has shown to be a useful tool for tracking of periodic reference signals and for compensation of periodic disturbances. The main advantages of the proposed circuitry are: 1) no digital conversion required; 2) easy tuning to the corresponding frequency; and 3) cost effectiveness. A description of the circuits and corresponding experimental frequency responses are given.