Robust repetitive controller design with improved performance

Presents the design of a digital repetitive controller with improved performance via a discrete-time μ-synthesis technique. The performance improvement at the fundamental frequencies is obtained by a modified lowpass q(z, z^-1) filter structure and robust stability is obtained through p-synthesis design methodology. The new structure of the q(z, z^-1) filter is motivated by efforts to square the sensitivity function which has very small values at the fundamental frequencies. The paper includes a robust repetitive controller design example for an electrohydraulic system for the noncircular cam turning process. Simulation and experimental results demonstrate the improved performance of the proposed design