Research On Adaptive Dynamic Output Feedback Fault-tolerant Control For Nonlinear Control Systems

With the development of science and technology,people pay attention to and pursue a higher sense of security and happiness.As far as the modern control system is concerned,it has the characteristics of large-scale and complex,so improving the safety and reliability of the system is an important prerequisite for our current research.Faulttolerant control as a means to ensure system security,it can still operate safely and stably in the case of system failure.Associated with the fault estimation technology,it can depict the shape and size of the fault online,so a large number of researchers are committed to finding an effective fault estimators.In this thesis,dynamic output feedback and adaptive fault estimator are combined,and unknown actuator faults are compensated by adjusting controller parameters adaptively.On the other hand,compared with linear systems,nonlinear systems are often more able to represent actual control systems.Especially,when the nonlinearity is non-Lipschitzian,its nonlinear systems can represent a wider range of nonlinear system models.Therefore,the study of more general nonlinear systems is extremely meaningful and valuable.The main work and research results of this thesis are as follows:(1)The fault-tolerant control problem of a class of nonlinear systems with unknown faults is investigated,where the nonlinearity is non-Lipschitzian,that is,the nonlinear system considered in this thesis is a more general nonlinear system model.An adaptive dynamic output feedback fault-tolerant controller is designed,which is composed of the measured output,the measured output derivative and the filtered information.The influence of actuator malfunctions are weakened by adaptive law and online tuning of dynamic output feedback gains to ensure the stability of the closed-loop systems.In addition,based on the designed controller,the coupling term can be reasonably eliminated and a lower stability condition can be obtained.The effectiveness of the method is verified by simulation examples.(2)On the basis of the existing nonlinear system theory in Chapter 3,for a class of time-delay nonlinear systems with faults,the nonlinearity does not need to satisfy the Lipschitz condition.An adaptive dynamic output feedback fault-tolerant control(FTC)is designed,which fully considers the measured output,the measured output derivative,filtered information and filtered time delay information,to compensate the influence of faults on the nonlinear system,so as to achieve the stability of the closed loop system when the actuator has faults.By combining the adaptive law with the dynamic output feedback,an adaptive dynamic output FTC is generated to ensure that the time-delay nonlinear system is asymptotically stable and meets the specified performance index.Finally,the lower stability condition of the closed loop nonlinear system is given.The feasibility of the method is verified by simulation examples.