DESIGN OF REDUCED-ORDER MULTIRATE INPUT COMPENSATORS FOR OUTPUT INJECTION FEEDBACK LAWS

Output injection feedback is a special kind of pole-positioning mechan ism whereby linear combinations of the output measurements are fed dir ectly into the plant's state. Using this mechanism, arbitrary closed-l oop pole assignment can be achieved so long as the plant is completely observable. In the event that output injection feedback is not possib le, a dual-observer-based compensator can be used to realize the pole- positioning effect of output injection. In this paper, we consider dis crete-time systems and derive the equivalent dual-observer-based compe nsator, herein termed a single-rate input compensator. Further, we exp lore the concept of multirate input sampling and show that a multirate input compensator (employing multirate sampling of the plant input) o f dimension much smaller than that of the single-rate input compensato r (employing single-rate input sampling of the plant input) can be des igned. Necessary and sufficient conditions for the existence of both t ypes of compensators are found. Design procedures for constructing the se compensators are also outlined.