HIGH-GAIN SAMPLED-DATA SYSTEMS - DEADBEAT STRATEGY, DISTURBANCE DECOUPLING AND CHEAP CONTROL

In this paper; it is shown that a sampled data system under a high gai n state feedback displays a two time-scale behaviour. The two time-sca le structure of the system is then used to study three seemingly diffe rent classes of problems. First, the pole placement problem is conside red and a two-step design based on the theory of singular perturbation is presented. Secondly, the asymptotic disturbance decoupling problem is solved using two different methods. The first method reduces the p roblem to one of an exact disturbance decoupling problem for the reduc ed-order model, while the second method shows that the problem can be solved by means of the output deadbeat response. The third problem con sidered in this paper is the cheap regulator problem where a near opti mal composite controller based on the optimal controllers of the slow and fast subsystems is constructed. For. all three problems, it is sho wn that by exploiting the two time-scale property of the system and so lving the problem in terms of two lower dimensional subsystems, the il l-conditioning and high dimensionality associated with the high gain f eedback system can be alleviated.