THE ROBUST TRACKING CONTROL OF NONLINEAR SYSTEMS WITH UNCERTAIN DYNAMICS

A robust tracking control algorithm based mainly on the theory of variable structure systems and Lyapunov's direct method is developed in this dissertation to treat tracking control problem of nonlinear time-varying system with uncertain dynamics. A nominal model instead of an exact one is used, together with a description of the bounds of plant uncertainty, and the objective is to design a control law that will drive all plants lying within the specified band of uncertainty to reach the goal. The modeling error, time-varying system dynamics, and disturbances are all treated as system uncertainties. This algorithm will much ease the difficulties in the need of precise model of physical system for the control purpose and handle nonlinear time-varying system with uncertainties.; The nonlinear time-varying system is first linearized to a linear time-varying system, with time-varying coefficients completely defined, via the method of variable structure systems. Then control method is switched to the Lyapunov's direct method to complete the tracking of the nonlinear time-varying system and eliminate the control chattering problem caused by the method of variable structure systems.; The tracking control of a simple two-link manipulator system is used as an example for the application of this robust tracking control algorithm.