Strong Tracking Filter And Its Application In Fault Diagnosis Of Nonlinear Systems

The fault diagnosis technology of dynamic system has obtained considerable development for 30 years. With the development of computer science and computation intelligence, many new methods and technology are introduced into this area. Up to now, most methods are proposed for linear systems, while in fact most systems are nonlinear, which causes a lot of new problems for linear system fault diagnosis methods. So the fault diagnosis of nonlinear systems appears and becomes the hotspot and difficulty of the research field of fault diagnosis and tolerant control.Strong tracking filter (STF) is a kind of nonlinear system fault diagnosis method based on parameter estimation. It deals with all faults of control system (such as component fault, actuator fault and sensor fault) as a fault of parameter deviation. Then by use of union estimation of state and parameter, quite accurate estimation of the states and parameters of nonlinear system can be obtained even though the model parameter doesn't match.First, a fault observer is introduced in this paper based on the theory of strong tracking filter. The simulation results prove that it has extremely strong tracking capacity with any change of the system parameters, and can obtain quite accurate estimation of the states and parameters. Then, aiming at a kind of component fault of nonlinear system, a PID control algorithm based on state estimation is achieved by combining the fault observer with digital PID control. The simulation results prove that this method has extremely strong tracking capacity of the states and parameters and can detect both faults of sudden change and slow change of system components in time. But it doesn't have tolerant control capacity of component faults. So a fuzzy adaptive PID fault tolerant controller based on state estimation is proposed in this paper by combining the fault observer with fuzzy adaptive PID control and modified Bayes algorithm. The results prove that the new algorithm has all merits of the method of PID control based on state estimation. At the same time, when parameter faults occur, the new algorithm can realize the fault tolerant control of system by the self-adjustment of PID parameter, which makes sure the system ran under a normal state.