Research On H_? Fault Estimation For Switched Time-delay Systems

With the development of modern science and technology, there is an increasing demand for the complex and large-scale systems to be more safe, reliable and effec-tive. For safety-critical systems, the faults may result in human mortality, environ-ment impact and economic loss. Therefore, fault diagnosis technology is essential for modern highly complicated control systems. Fault diagnosis systems are used to detect faults and diagnose their location and significance in systems. A fault must be diagnosed as early as possible even it is tolerable at its early stage, so that any serious consequences can be avoided.On another research front, it is more effective to describe complex engineering systems with inherently multimodal or variable structures as switched systems, such as the biochemical processes, the computer control systems and the communication industries. Compared with general systems, switched systems have the characteris-tics of complexity and peculiarity. Therefore, the study on switched systems is of great practical importance as well as theoretical significance, and has attracted ex-tensive attention over the past two decades. However, most of the important results obtained are concerned with stability analysis and controller design, the problem of fault diagnosis for switched systems are still open and challenging. Therefore, mo-tivated by the proceeding discussion, the topic of this research is focused on "Fault Estimation for Switched Time-delay Systems"Chapter 2 is concerned with the problem of fault estimation for switched Lur'e systems with common Lyapunov functions approach. The main object is to design an observer-based fault estimator to ensure a prescribed H?performance level. Suf-ficient delay-dependent existence conditions of the fault estimator are obtained by solving a set of linear matrix inequalities. Furthermore, a feasible solution to the H?fault estimator gain matrices is proposed.Chapter 3 addresses the problem of fault estimator design for switched time- delay systems with impulsive control. The impulsive behavior is introduced into a hybrid controller, which generates a novel class of hybrid systems called switched impulsive control systems. Some delay-dependent sufficient conditions are derived on the existence of the hybrid controller by using multiple Lyapunov functional ap-proach. In addition, based on cone complementarity algorithm, the solutions to ob-server gain matrices and the impulsive matrices are obtained by solving a set of linear matrix inequalities. Numerical examples are given to illustrate the effectiveness of the proposed approach.Chapter 4 studies the problem of fault estimation for switched Lur'e systems based on minimal dwell time approach. The problem is formulated as to find a fault estimator to ensure both the absolute stability and a prescribed L2-gain bound of an augmented system from the original system and the fault estimation error system. Some delay-dependent sufficient conditions on the existence of an H?fault estima-tor are derived. Associated solutions to the problem are obtained, and the minimal dwell time constraints are imposed for the switching rule.Chapter 5 deals with the problem of fault estimation for a class of switched nonlinear systems of neutral type with average dwell time approach. By employ-ing a switched observer-based fault estimator, the problem is formulated as an H?filtering problem. Sufficient delay-dependent existence conditions of the H?fault estimator are given in terms of certain matrix inequalities. Moreover, the parameter matrices of the fault estimator and the suitable switching rule are obtained by using cone complementarity algorithm. Numerical examples are provided to demonstrate the effectiveness of the proposed approach.Chapter 6 investigates the problem of reduced-order fault estimator design for a class of switched nonlinear systems with time-varying delay. A generalized form of the observer-based reduced-order fault estimator is employed. Based on the aver-age dwell time approach and the Lyapunov functional technique, a sufficient delay-dependent criterion on the existence of the estimator is derived to ensure the expo-nential stability and a prescribed L2-gain bound of the error system. Furthermore, the parameters of an admissible estimator are obtained from the solution of a convex optimization problem. Numerical examples are provided to illustrate the effective-ness of the proposed results.