A QFT approach to robust dual-rate control systems

A dual-rate control system is a hybrid system composed of continuous-time and discrete-time elements with two sampling frequencies. In this work, a new frequency domain analysis and design approach, based on the quantitative feedback theory is developed, to cope with robust stability and robust tracking specifications. Tracking specifications are considered not only in the discrete-time but also in continuous-time, that allow a precise description of the intersample behavior (ripples), and characterization of frequencies below and beyond the Nyquist frequencies. Several illustrative examples and a case study has been developed.