Designing robust repetitive controllers

A method for designing repetitive feedback controllers using nonparametric frequency response plant models is developed. In comparison to the zero-phase-error (ZPE) controller (ASME J. Dyn. Syst. Meas. Control, 111, pp. 353-358), this method has the added benefit of providing improved transient performance when the plant inverse is unstable. In this controller design process, a connection is made between model uncertainty and the desired frequency response of the so-called q filter. Also, it will be shown that an optimal equiripple filter is useful when designing high-order q filters. The entire process was experimentally verified on an engine control application. A repetitive controller was used to determine the dynamic fueling requirements of a fuel injected, spark-ignition engine subjected to periodic changes in the throttle position. This fueling information is necessary when designing feedforward fueling algorithms.