Adaptive Tracking Control Design For Switched Nonlinear Time-varying Systems

As a typical class of hybrid systems,switched systems have attracted a great deal of attention because of their importance from both theoretical and practical points of view.A switched system is a dynamical system that consists of a finite number of subsystems and a switching signal governing the switching among them.Many practical systems can be modeled as switched systems,such as flight control systems,network control systems,and so on.On the other hand,compared with nonlinear time-invariant systems,nonlinear time-varying systems have a more general structure,therefore,the study of nonlinear time-varying systems has important significance both in theory development and engineering applications.Based on the current research status of nonlinear switched time-varying systems,the problems of stabilization,tracking control and output-feedback control are investigated by exploiting switched systems theory,backstepping,the common Lyapunov function(CLF)method,the prescribed performance control(PPC)and the adaptive control method.The main results of this thesis are summarized as follows:(1)For a class of nonlinear time-varying switched systems with lower triangle structure,the decentralized adaptive tracking control and prescribed performance are studied.A main result about adaptive control for switched non-linear time-varying systems with unknown time-varying parameters is established using a constructive design method for the first time,a sufficient condition for the adaptive tracking problem is derived by exploiting the common Lyapunov function method and adaptive backstepping method.Also,the difficulties caused by the existence of unknown time-varying parameters in the process of controller design are solved using adaptive control and common Lyapunov function method.State feed-back controllers for subsystems are designed ensuring that all states in the closed-loop are globally uniform and ultimately bounded under any switching.Finally,simulation experiments are carried out based on a double inverted pendulum model to verify the effectiveness of the proposed control strategy.(2)For a class of nonlinear switched time-varying systems,the problem of adaptive output feedback control is studied.A set of switched K-filters is constructed to estimate the unmeasurable states.An adaptive output control scheme is proposed to eliminate unknown time-varying parameters and unknown disturbances caused by actuator faults using adaptive control,backstepping recursive and common Lyapunov function method.By constructing switched output feedback controllers for subsystems,the stability of the closed-loop system under arbitrary switching is guaranteed.Finally,the effectiveness of the scheme is verified by simulation.The conclusions and perspectives are presented in the end of the thesis.