Research On Fault Detection And Fault-tolerant Control Of Several Networked Control Systems

The control systems that control loops are closed through communication network are called networked control systems (NCS). It aims to ensure data transmission and coordinating manipulation among spatially distributed components of the system. NCS have enormous advantages, such as less wire and volume, lower cost, easy installation and maintenance, etc. However, the complexity introduced by communication networks makes the analysis and design of the system complicated, and this kind of system has higher level of demands for safety and reliability. This dissertation focuses on the fault detection and fault-tolerant control problems for several kinds of NCS with network delay and data packet dropout. The model-based fault detection method and the fault-tolerant controller design method for the system are proposed so as to increase safety and reliability of the NCS and to provide a theoretical backbone for its engineering applications. The main contributions can be enumerated as follows:First, the observer-based fault detection method for NCS with networked introduced delay and fixed rate of data packet dropout is proposed. Based on the asynchronous dynamical system theory, the sufficient condition of exponential stable for the fault observer system is presented, and the fault observer design method is also provided. In addition, for the NCS with unknown rate of data packet dropout, the robust fault detection approach is provided. The system is modeled as Markovian jump system with four operation modes. The design method for fault detection filter is proposed to insure the mean-square stability for the residual generation system and attenuate the disturbance to a prescribed level. Furthermore, by considering parametric uncertainties and actuator continuous gain faults, the necessary and sufficient condition of mean-square stable for the closed loop faulty system is given and the fault-tolerant controller design method is proposed.Second, the robust fault detection method and fault-tolerant controller design approach is provided for NCS with Markovian delays. The residual generator is constructed so that the fault detection problem can be formulated as an H∞filtering problem. A sufficient condition to solve this problem is established in terms of the feasibility of certain linear matrix inequalities (LMI), and the fault detection filter gain design procedure is proposed. Based on the same NCS model, the dynamic output feedback fault-tolerant controller is designed by using cone complementary technology.Third, for multi-actuator failures, the fault-tolerant control strategy for NCS with Markovian packet dropout is given with stability guaranteed. The guaranteed cost passive fault-tolerant controller for the system is designed. Then, with consideration of control performance and different actuator failure model, the design procedure of the active fault-tolerant controller for NCS with packet dropout is proposed.Fourth, the design approach of guarantee cost fault-tolerant controller and robust H∞fault-tolerant controller is proposed for continuous-time NCS with time-delay and packet dropout. By introducing integral-inequality and slack variables methods, the sufficient condition for the existence of the guaranteed cost controller in terms of matrix inequalities is obtained and the guaranteed cost robust fault-tolerant controller is designed. Furthermore, by introducing new Lyapunov functional, the less conservative robust stability conditions for system with parametric uncertainties are obtained, and the robust H∞fault-tolerant controller that achieves the prescribed disturbance attenuation level is also designed.Fifth, based on a nonlinear NCS approximated by T-S fuzzy models, the fault detection and fault-tolerant control problems for a class of nonlinear NCS with time-delay and packet dropout are studied. The fault detection observer is designed such that the residual signal is sensitive to the fault but robust to exogenous disturbance for a certain level. Then, the fuzzy robust H∞fault-tolerant controller is designed for the nonlinear NCS with parametric uncertainties. The robust stability conditions are obtained based on delay-dependent approach. An algorithm is given to get a feasible solution to the fuzzy fault-tolerant controller gain by using a cone complementary technology.Finally, some open issues and the future work in fault detection and fault-tolerant control of NCS are discussed.