Research On Intelligent Adaptive Control For Nonlinear Systems With Actuator Faults

With the development of science and technology,people pay more attention to the security and reliability of the control systems.On the other hand,since there are inevitably some failures existing in many practical control systems,fault-tolerant control methods and theories have also emerged and developed rapidly.Fault-tolerant control is through the relevant fault compensation measures to make that the controlled system can still run well when the failures occur,so that fault-tolerant control can eliminate the impact of the failure.Therefore,the study of fault-tolerant control of nonlinear fault systems has important theoretical significance and practical value.In this thesis,for several classes of nonlinear systems with unknown actuator faults,the fault compensation mechanism is established,and several fuzzy adaptive fault-tolerant control methods are given based on backstepping recursive control design and fuzzy control theory and in the sense of finite time stability.The stability,convergence and robustness of the closed-loop system are proved.The main content of this thesis are as follows:(1)For a class of single-input-single-output uncertain nonlinear systems with actuator faults,fuzzy logic systems are used to model the controlled systems,and a fault compensation mechanism is established.Combining fuzzy adaptive control with backstepping recursive control design,an adaptive fuzzy fault-tolerant control scheme is presented in the framework of finite time control design theory.Based on Lyapunov stability theory,the stability,convergence and robustness of the closed-loop system are proved.Finally,the validity of the theoretical result is verified by numerical simulations.(2)For a class of uncertain nonlinear systems with block triangular structure and actuator faults,the fuzzy logic system is used to model the controlled system,and a fault-tolerant compensation mechanism for actuator faults is given.A fault tolerant controller is designed by combining fuzzy adaptive control with backstepping recursive control technique.It is proved that the proposed fault-tolerant control scheme can guarantee the stability,convergence and robustness of the closed-loop system based on the finite time Lyapunov stability theory.The validity of the theoretical result is verified by numerical simulations.(3)For a class of multi-input and multi-input uncertain nonlinear systems with actuator faults and unmeasured states,fuzzy logic systems are used to approximate the unknown uncertain dynamics,and a fuzzy state observer is established to estimate the immeasurable states.A fault compensation term is designed to overcome the influence of the system faults.Based on the designed fuzzy state observer and the backstspping control design technology,controller scheme and fault compensators are given.It is proved that the proposed control method can guarantee all signals of the closed-loop system to be semi-global and practically stable in finite time.The validity of the theoretical results is verified by numerical simulations.