Study Of Fault Diagnosis And Fault Tolerant Control For Switched Systems

Switched system is a dynamic system which consists of finite subsystems and a switchingsignal. In practical engineering systems, many real world process and systems can be modeled asswitched systems, such as electrical systems, chemical systems, aeronautics and astronautics,network communication and so on. Therefore, the study of linear time-invariant switched systemstheory is gradually formed and developed, which provides fundamental theoretical support for theother complex multiple modes switched systems. However, the theoretical study about linearswitched systems is remain not perfect, most results are concerned on the stability,H controletc, especially the study on fault diagnosis and fault tolerant control for switched systems is few,which tremendously limited the application in the engineering field.Based on the stability research results of linear switched systems and the observer method, thisdissertation investigates the fault diagnosis and fault tolerant control for linear switched systems.The first step of fault diagnosis is fault detection, its task is to detect whether the fault hashappened in a system; once the fault happened, the next step is to estimate the magnitude of thefault, which is called fault estimation. Compared with fault detection, fault estimation is morecomplex and difficult. Based on the on-linear fault estimation information, the feedback controllercan be designed to realize the stability of a system. This dissertation studies the problems of faultdetection, fault estimation, fault accommodation and reliable control for linear switched systems,and establishes a systemic framework of fault diagnosis and fault tolerant control for linearswitched systems, the main contributions can be summarized as follows:Firstly, based on the stability theory of discrete-time switched systems, fault detection problemis investigated for discrete-time switched systems with time-varying delay case and intermittentmeasurements case. The dissertation extends the constant delay case to time-varying delay case,and supposes the random output is a Bernoulli distributed white sequence. The main idea is tofault detection filter design problem formulated asH filter problem. By applying linear matrixinequality technique, efficient conditions are deduced and proved, and a simulation example isprovided to illustrate the effectiveness of the proposed approach.Secondly, it is a common phenomenon that asynchronous switching occurs in practicalcontinuous-time switched engineering systems, which means the observer is asynchronous withthe original system. The asynchronous fault detection filter design problem is studied. By utilizingpiecewise Lyapunov function and average dwell time techniques, the fault detection filter design problem is formulated asH filter problem. The parametric solution of fault detection filter isgiven for the continuous-time switched systems, and simulation results prove the correctness ofthe obtained results.Thirdly, sensor fault estimation and compensation approaches are investigated forcontinuous-time time-delay switched systems. Based on descriptor observer approach and linearmatrix inequality technique, a novel time-delay switched descriptor state observer is proposed toestimate both the state and sensor fault. The proposed observer technique is also extended tosystems with nonlinearities. To be worth mentioned that the proposed method can estimate thesensor fault in any forms, such as constant, time varying, and even unbounded. Then, based on theestimation of the sensor fault, an efficient fault-tolerant operation can be realized via sensor faultcompensation.Fourthly, the actuator fault estimation and accommodation for time invarying and time varyingdelay continuous time switched systems are studied. Based on adaptive observer and averagedwell time methods, a novel fast adaptive fault estimation algorithm was proposed. The proposedfault estimation algorithm can suit to constant fault and time-varying fault. On the basis of faultestimation, an observer-based fault tolerant controller is designed to guarantee the stability of theclosed-loop system.Finally, actuator reliable controller design problem for discrete time switched systems withstable and unstable subsystems is considered. By applying average dwell time and linear matrixinequality techniques, observer-based reliable controller design approach is given, and an exampleis included to demonstrate the effectiveness of the proposed approach.