Adaptive Fuzzy Robust Control For Switched Uncertain Nonlinear Systems

With the process of science and technology,switched systems have considerable applications both in engineering and real life.Therefore,the researches of switched systems have important theoretical significance and broad application prospects.In this thesis,based on the fuzzy adaptive backstepping recursive design method,the controller design and stability analysis are presentted for several kinds of switched uncertain nonlinear systems.The main works are as follows:(1)For a class of switched nonlinear systems with input quantization,under the condition of the unknown nonlinear functions,hysteretic quantised input,the switching signals and partially measurable states,by combining with the separation technique of the nonlinear functions,the hysteretic quantised input is divided into two bounded non-linear functions in the control design to solve the chattering problem,a new robust adaptive fuzzy control design method is proposed.By combining with adaptive backstepping technique,the control design for the fuzzy switched systems has been achieved,the stability and convergence of the closed loop system can be guaranteed via Lyapunov stability theory and average dwell time method.Finally,the effectiveness of the proposed approach is verified by the simulation examples.(2)For a class of switched nonlinear systems with unknown delays,the unknown nonlinear dynamics,unknown time-varying delays,partially measurable states and a batch of switching signals are included,in the average dwell time switching rules,a new fuzzy output feedback control method is presented.By combining with adaptive backstepping technique,the control design for the fuzzy switched systems has been achieved.It is proved that the stability and convergence of the controlled system can be guaranteed via Lyapunov stability theory and Lyapunov-Krasovskii functional theory.Finally,the simulation results are presented to verify the validity of the raised control method.(3)For a class of switched nonlinear systems with unknown control directions,in the case of the unknown nonlinear dynamics,unknown control gain,partially measurable states and switching signals,in the average dwell time switching rules and by combining with adaptive backstepping technique,Nussbaum gain technique and Prandtl-Ishlinskii models are introduced to get over the unknown control gain problems,the control design for the fuzzy switched systems has been achieved.It is proved that the stability and convergence of the controlled system can be guaranteed via Lyapunov stability theory and average dwell time method.Finally,the simulation results are presented to verify the validity of the proposed control scheme.