Fault Diagnosis For Dynamic Systems

Fault detection and diagnosis of nonlinear systems has been received more and more attention in recent years. Some correlative issues in this area are studied in this paper, such as the fault detection and diagnosis for some uncertain nonlinear systems. The methods are based on a series of control theories, which include Lyapunov stability theory, adaptive control theory, sliding mode control theory, neural network theory, and so on. Based on observer methods, some fault diagnosis schemes are studied. The main work in this paper is summarized as follows.Firstly, a robust fault diagnosis for a class of nonlinear many time delay uncertain system is proposed. Nonlinearity is related with inputs and states, uncertainties include states and outputs. System states and outputs are estimated by the technology of designing observer and method of producing robust threshold is educed. A adaptive tracker is designed which tracks fault when difference between system output and estimated output equals or surpass threshold. Robustness, sensitivity and stability are analyzed. Simulation results demonstrate this method feasible.Secondly, a fault diagnosis method based on sliding mode is presented for a class of nonlinear system. Sliding mode term ensures that the observer has robustness under non-trouble conditions, and fault detection can be realized by making use of sliding boundary size. When the fault has been detected, the estimation part in the observer for the fault is enabled. A radial basis function neural network is used to approximate the fault, so fault diagnosis can be finished online. Simulation results show the feasibility of the proposed approach.Lastly, a method on learning approach is considered in solving the issues of detectability conditions and detection time of fault diagnosis for a class of nonlinear uncertain system. The method designs observer which can be used for detection, identification and accommodation of failures in dynamical systems. The robustness is proved ,the detectability conditions as well as the upper bound of detection time are given theoretically.Through the research in this paper, the fault detection and diagnosis problems for several classes of uncertain nonlinear systems have been properly solved. By making use...