Robust Fault-tolerant Control Of Several Classes Of Switched Systems

Switched systems, as a special but very important class of hybrid systems, have extensive applications in indurstrial fields such as power systems, chemical engineering and aeronautics and astronautics. As known, these systems have uncertainties and it is unavoidable that faults may occur on the components of these systems. If we ignored these uncertainties and faults while designing controllers for these systems, it would result in precision inaccurities, ossilations, even leading to instability. Thus it can seriously affect stability, reliability and security of these systems. Therefore, it is of necesscity and importance of investigating robust fault-tolerant control of switched systems which has extensive indurstrial applications. However, it makes robust fault-tolerant control of switched systems be a very chanlleging topic that the fact that switched systems have the feature of continuous states and discrete events and that system uncertainties and occurance of the faults are unpredictiable and thus there are only a few results in the literature. This dissertation studies robust fault-tolerant control of uncertain switched systems with faulty actuators and makes several contributions on this challenging topic. The main results are listed as follows:First, this dissertation gives a brief introduction of concepts, commonly-used methods and new developments of switched systems, robust control and fault-tolerant control.Secondly, robust fault-tolerant guaranteed cost control and H? control problems are studied with the multiple Lyapunov function technique for a class of uncertain linear switched systems. First the definition of robust fault-tolerant guaranteed cost control of this class of switched systems is introduced, then a sufficient condition is given for stabilization against actuator faults. Similarly, we studied its H? control also with the multiple Lyapunov function technique. Finally, as a special case of the above H? control problem, a hybrid robust fault-tolerant H? controller is designed for a class of linear switched systems for which continuous controllers cannot achieve its H? control problem.Thirdly, a robust fault-tolerant control method is proposed with the aid of the average dwell-time method for a class of linear switched time-delay systems. First the stabilization of this class of switched systems is realized and followed by an explicit formulation for estimation of the norm of the states. Furthermore, this result is applied to a river pollution control model for its robust fault-tolerant control problem to force the concentrations of the biochemical oxygen demand and dissolved oxygen to follow their desired values.Later on, a new state-feedback control method is proposed for global stabilization of a class of switched cascade nonlinear systems with both faulty actuators and structural uncertainties. The proposed method is independent of arbitrary switching polices. The simulation studies are given for the longitudinal dynamics of an F-18 aircraft operating on different heights to realize the objective of its attact angle and pitch rate following the desired position.After that, an average dwell-time based approach is proposed for fault-tolerant control of the same class of switched nonlinear systems as above. the proposed controller, independent of switching rules, exponentially stabilizes this class of switched nonlinear systems with actuator faults provided that the average dwell time is greater than a certain positive constant. A numerical example is given to show the effectiveness of the proposed method.Following the above results, two fault-tolerant control methods are presented to deal with occurance of partial faults of the acutators of a class of switched cascade nonlinear systems whose nonlinear subsystem has structural uncertainties satisfying the linear growth condition. Two techniques are used for the two control methord, respectively. One is the common Lyapunov function method and the other is the average dwell-time method. Simulation studies on a practical haptic display system with switched virtual environments and two numerical exapmeles are provided to verify the effectivenss of the two methods.Finally, the conclusions and perspectives end the dissertation.