Estudo de sistemas de controle a estrutura variável

Abstract

Study of a class of adaptive control systems: the Variable Structure Control Systems. A control system is said to be of variable structure if the structure and/or the parameters of the controller varies, the parameters variations being discontinuous, depending on the state, and/or the perturbations of the controlled system. For this study, some results obtained by Fillipov about the differential equations with discontinuous right-hand side are used. For the case of single input-single output linear systems, a detailed analysis of the essential properties and advantages of variable structure control systems is done. An important characteristic of these systems, is the possibility of sliding regimes, when the controlled system becomes invariant. An extension of Liapunov's second method is used for the stability study, and the analysis of the relationship between the sliding regime condition, and the stability of an invariant set, which is the sliding surface itself.