Research On Observer-based Fault Detection Methods For Switched Systems

With the increasing complexity of system and equipment,only using a continuous dynamic model or a discrete event model is not enough to accurately describe and analyze the dynamic propagation of system.Therefore,the theory of hybrid systems has emerged and achieved rapid development.Switched systems are a kind of typical hybrid systems that include some subsystems and a switching signal.The current studies about switched systems mainly focus on stability analysis of switched systems,whereas there are limited results on fault detection for switched systems.In view of this,fault detection for switched systems is studied in this thesis.The main contents of this thesis are given as follows:Based on unknown input observer design,this thesis studies fault detection methods for switched systems with unknown input disturbance,which can be decoupled completely.First,fault detectors for linear switched systems are constructed based on unknown input observers,and parameters of fault detectors ar e designed by using the average dwell time technique and multiple Lyapunov functions method.Moreover,this method is extended to nonlinear switched systems with unknown input,and parameters of fault detectors are designed by using the average dwell time technique,Lipschitz condition and multiple Lyapunov functions method.Fault detection method for switched systems is studied based on H_/H? fault detection observers.Firstly,for the linear switched systems with unknown input disturbance that cannot be decoupled,H_/H? fault detectors are constructed based on state observers.And the design problem of fault detectors is formulated as solving multi-objective problems of error system within the constraint of weighted H_/H? mixed performance indices.Then,the slack matrices are introduced to reduce the conservativeness of multi-objective H_/H? design problem.Moreover,this method is extended to fault detection of linear uncertain switched systems.Fault detection method for switched systems is studied based on H_/H? unknown input observers.A fault detector based on H_/H? unknown input observer is proposed for the linear switched systems with partially decoupled unknown input disturbance.A part of unknown input disturbance is decoupled using this method,so that the effect of unknown input disturbance on residual is reduced and the performance of fault detection is improved.Fault detection method for switched systems is studied based on H_/H? asynchronous fault detection observers.For the linear switched systems with non-zero control input,asynchronous switching phenomenon between the switched subsystems and fault detectors is considered,and H_/H? asynchronous fault detectors are proposed based on state observers.The fault detectors design problem is formulated as solving multi-objective problems of augmented error systems within the constraint of weighted H_/H? mixed performance indices,parameters of H_/H? asynchronous fault detectors are designed.For fault detection of linear switched systems with interval time-varying delays,fault detection method based on delay dependent H_/H? fault detection observers is investigated in this thesis.First,delay dependent H_/H? synchronous fault detectors are presented based on state observers.Then,considering that time delays and asynchronous switching coexist,delay dependent H_/H? asynchronous fault detectors are proposed based on state observers.Besides,average dwell time method and the multiple Lyapunov-krasovskii functionals are applied in designing the parameters of fault detectors.