An Adaptive Repetitive Control Scheme for Tracking periodic Signals with Unknown Period

This paper presents an adaptive repetitive control scheme for asymptotic tracking of periodic signals with unknown period. A discrete-time recursive scheme for identifying the period of a periodic signal with resolution better than the signal sampling interval is presented. An indirect adaptive digital repetitive control based on the identified period is proposed. With a fine tuning in the sampling time, the signal period is adjusted to integer multiples of the sampling time. This exact synchronization between the signal period and the repetitive control period makes a better tracking performance than that of fixed sampling time repetitive controller. Both simulation and experimental results are presented to demonstrate the effectiveness of the proposed control scheme.