Fault-tolerant Control Of Several Types Of Nonlinear Switched System

In recent years,fault-tolerant control of system has attracted much attention of researchers.With the rapid development of advanced control technology,people have higher and higher requirements for the performance of the system,and its related control system becomes more and more complex.In many complex systems,some catastrophic faults usually occur,such as unknown actuator/sensor faults.Therefore,it is very meaningful to improve the reliability of the system by proposing fault-tolerant control strategy to reduce or even eliminate the effect of the fault for the system.This paper investigates several classes of nonlinear switched systems with unknown actuator/sensor faults.Using fuzzy logic systems to approximate the unknown nonlinear functions.Several adaptive fuzzy output feedback fault-tolerant control schemes are proposed by Lyapunov function method and backstepping technique.The main work is as follows:(1)The problem of adaptive fuzzy output feedback fault-tolerant tracking control is investigated for a class of uncertain nonlinear switched systems with unknown sensor fault.Since the sensor may suffer from an unknown constant loss scaling failure,this paper considers the situation where only the actual output can be used for feedback design.The failure factor represents the loss of effectiveness faults.The adaptive estimation coefficient is introduced to estimate the failure factor,then a state observer is constructed to estimate the unmeasured state by the actual output.The research shows that the proposed fault-tolerant control scheme with average dwell time constraints can ensure that all states of the closed-loop system are semi-global uniform ultimately bounded and the tracking error converges to a sufficiently small neighborhood of zero.Simulation example shows the effectiveness of the scheme.(2)The problem of adaptive fuzzy output feedback fault-tolerant tracking control is investigated for a class of uncertain nonlinear switched systems with sensor and actuator faults.Both the faults considered are unknown,which makes the control design more complex and difficult.The adaptive estimation coefficient is introduced to mitigate the effect of sensor faults,then a state observer is constructed to estimate the unmeasured state and eliminate the effect of actuator faults.In this paper,it is proven that the proposed control scheme with average dwell time constraints can ensure that all states of the closed-loop system are semi-global uniform ultimately bounded and the tracking error converges to a sufficiently small neighborhood of zero.The effectiveness of the scheme is verified by a simulation example.(3)The problem of decentralized fuzzy adaptive output feedback fault-tolerant tracking control is investigated for a class of nonlinear switched large-scale systems with sensor and actuator faults.Considering that only the actual outputs are measurable when the sensor faults occur,a noval state observer is designed to estimate the unmeasured state and eliminate the effect of actuator faults.The Lyapunov stability principle proves that the designed decentralized fault-tolerant controllers can ensure that all states of the closed-loop system are semi-globally uniform ultimately bounded and the tracking errors can converge to a sufficiently small neighborhood of zero.Simulation example shows the effectiveness of the scheme.