Discrete-Time Repetitive Control System Design Using the Regeneration Spectrum

The stability, transient response, and stability robustness of discrete-time repetitive control systems characterized by large values of the time delay inherent in such systems are examined here using a function of frequency termed the regeneration spectrum. The ability to infer different aspects of controlled system performance from the regeneration spectrum, and its ease of computation, makes it a valuable tool for controller analysis and synthesis. A design procedure for discrete-time repetitive control systems, based on the regeneration spectrum, is outlined and a controller form suggested to effectively handle the trade-off between the different aspects of controlled system behavior. The controller design procedure is applied to an electrohydraulic material testing application characterized by strong nonlinearities, and shown experimentally to be effective in improving the controlled system performance.