Robust and adaptive repetitive control

Repetitive control is useful if periodic disturbances act on a control system. Perfect (asymptotic) disturbance rejection is achieved if the period-time is exactly known. For those cases where the period-time changes and can not be measured directly by an auxiliary signal, a robust repetitive controller structure is proposed. It uses multiple memory-loops in a certain feedback configuration, such that small changes in period-time do not diminish the disturbance rejection properties. For larger changes of the period-time a new self-tuning method is proposed, based on correlation analysis. Both the robust and the adaptive repetitive controller show good implementation results for a tracking control problem of a Compact Disc player