An Adaptive “quasi” Repetitive Controller for the Fundamental Frequency Estimation of Periodic Signals

A repetitive control scheme for asymptotic tracking of the fundamental frequency of periodic signals is presented. The method uses an adaptive orthogonal signals generator based on a second order generalized integrator for identifying the fundamental frequency of the signal with accuracy depending on the adaptive gain. The robustness of the repetitive controller is established by investigating its sensitivities with respect to an inaccurate estimation of the period.