VARIABLE STRUCTURE CONTROL OF INTERCONNECTED NONLINEAR SYSTEMS (DECENTRALIZED)

This thesis develops a method of control for a class of nonlinear, large scale systems which is more robust than conventional linearization techniques. By use of a switched control law, variable structure control (VSC) forces a system's state trajectory onto a manifold (the sliding surface) in the state space. An additional advantage of VSC is that the design procedure is divided into two smaller problems. By proper selection of the sliding surface, the system restricted to the sliding surface satisfies conventional goals of control theory, such as stability, tracking, etc. By the proper use of generalized Lyapunov stability, one may construct a set of switched controls to drive the state trajectory to and maintain it on the sliding surface. The contributions of this thesis include: (i) the compilation of several VSC design methods which are applicable to input linearizable systems; (ii) the extension of VSC design from hand oriented design methods for low order systems to numerical techniques applicable to large scale systems; (iii) the extension and generalization of decentralized variable structure control (DVSC) from single input subsystems in canonical form to multi-input subsystems in more arbitrary form; (iv) the presentation and solution of a tracking problem for nonlinear systems, using both centralized and decentralized VSC; (v) the solution of a tracking problem involving decentralized control of two interconnected power systems.