Robust Fault Estimation And Active Fault Tolerant Control For Uncertain System

The increasing demand for reliability,safety and efficiency has led to unprecedented chanllenges for modern complex engineering systems' operation.These conditions significantly increase the possibility of the faults in components or subsystems.Potential faults may cause the whole svstem fails and even serious losses.Due to the uncertainties of complex plant models and the external disturbance,it is difficult to satisfy the performances above.Therefore, the robust fault diagnosis and fault-tolerant control (FTC) for dynamic systems has obtained greater attention and it is important to ensure the complex systems'reliability and safety.In this thesis,the problems of robust fault detection and FTC for several types of uncertain systems are studied.The main research results are given as follows:This paper presents a survey on fault tolerant control techniques based on analytical models of nonlinear systems.It concerns mainly two kind of methods:active fault tolerant control technique based on adaptive parameter estimation technique or intelligent methods,and passive fault tolerant control based on Hamilton- Jacobi equations.An approach is presented to roubstly detect fault of nonlinear systems with uncertainty of modelling errors,noise and disturbance.This approach is based on first usingradial basis function networks to process signal and filter noise,and propagating the uncertainties'effect of interval models with parameters expressed by intervals into residuals;then comparing the models with measurements obtained from amonitored process and using the principle of adaptive thresholds to achieve robustness.Then an example of aconvection heating surface of a 300MW power station boiler is discussed.Simulation results have demonstrated that this method is effective and efficient for online fault detection due to its sensitivity to early fault detection and robustness of modeling error and noise.obust fault-tolerant control problem is discussed on the norm bounded parameter perturbation of uncertain linear systems,a sufficient condition ahout robust and completeness ofhe closed-loop system is given in the uncertain linear systems existing for actuator failure by using algebraic method.Finally,a numberical example shows the method is simple and effective.