DESIGN OF REDUCED-ORDER MULTIRATE OUTPUT LINEAR FUNCTIONAL OBSERVER-BASED COMPENSATORS

Often in control system design, it is only necessary to estimate a sin gle (but prespecified) linear function of the system's state for the p urpose of implementing a feedback control law. This can be achieved by a linear functional observer which may have order one less than the o bservability index of the plant, but generically cannot have smaller o rder. In this paper, we explore the concept of multirate output sampli ng and show that a linear functional observer-based compensator employ ing multirate sampling of the plant output can be designed with dimens ion much smaller than that of the linear functional observer-based com pensator employing single-rate sampling of the plant output. Necessary and sufficient conditions for the existence of the single-rate and mu ltirate output linear functional observer-based compensators are found . Design procedures for constructing these observer-based compensators are also outlined. Furthermore, both types of compensators are strict ly causal and open-loop stable for sufficiently small frame period, T- 0.