Fault Detection And Fault-tolerant Control For Networked Control Systems

The fault detection and fault-tolerant control for networked control systems (NCSs) are studied in this dissertation. The main researches are concluded as follows:(1) The fault detection and guaranteed fault-tolerant control for networked control systems with short output delay and short control delay are studied. Supposing that the sensor and controller nodes are time-driven and the actuator node is event-driven, the system is modeled as a discrete time system with parametrical uncertainties. Firstly, considering the system with disturbances, the problem of the fault detection is discussed. The robust H∞fault observer of the system is designed according to the time-delay compensation strategy. Then the stability condition of the observer system is given by using the approaches of Lyapunov and Matrix Inequalities, and the robustness and sensitivity are analyzed. Secondly, considering the system with data packet dropout, the problem of the fault detection is discussed. The fault observer composed of open-loop observation and close-loop observation is proposed. Under fixed packet dropout rate, the observer error system is equivalent to an asynchronous dynamical system and based on asynchronous dynamical system theory and the approach of Matrix Inequalities, the condition for exponential stability of the system is given. Thirdly, based on observer, the problem of integrity against sensor failures for the networked control systems with short output delay and short control delay is discussed. The state observer of the system according to the time-delay compensation strategy is designed. Then, considering possible sensor failures, an augmented mathematic model for the networked control systems based on observer is developed. In terms of the given quadratic performance index function, the integrity condition of the system is given and the designs for guaranteed cost fault-tolerant controller and observer are presented respectively by using the cooperative design approach of the controller and observer and the approach of Matrix Inequalities.(2) The fault detection and guaranteed fault-tolerant control for networked control systems with long time delay are studied. Firstly, the problem of the fault detection for the networked control systems with long output delay and data packets dropout is discussed. The discrete mathematical model is set up under the existence of asynchronous clock between the actuator and the sensor. Based on the model, the fault observer of the system is designed, according to conditions of data arrival of the controller, and the observer error system is equivalent to a discrete switched system with parametrical uncertainties. Then the stability condition of the system is given with the switched system theory and the approach of Matrix Inequalities. Secondly, based on observer, the problem of integrity against sensor failures is discussed supposing the networked control systems with control delay and both output delay and control delay, respectively. For the networked control systems with control delay, the state observe is designed and for the networked control systems with both output delay and control delay, the observer with delay compensation is constructed. Then according to possible sensor failures, an augmented mathematic model for the networked control systems based on state observer is developed respectively. In terms of the given quadratic performance index function, the integrity condition of the system is given and the designs for guaranteed cost fault-tolerant controller and observer are presented respectively, by using the cooperative design approach of the controller and observer and the approach of Matrix Inequalities.(3) The fault-tolerant control for nonlinear networked control systems is studied. The nonlinear networked control systems which plant can be described by T-S fuzzy models is modeled as a discrete time T-S fuzzy model when the network-induced delay is uncertain short time-varying delay. Then based on the model, the fuzzy state observer is designed and considering possible sensor failures, the sufficient stability condition of integrity against sensor failures is given and the designs for fuzzy fault-tolerant controller and fuzzy observer are presented by using the theory of fuzzy control and the approach of Matrix Inequalities. Then the H∞fault-tolerant control for the system is also studied and a fuzzy fault-tolerant controller and a fuzzy observer satisfying the H∞performance index are designed.(4) The fault-tolerant control for networked control systems under variable-period sampling based on the continuous-time model is studied. Assuming that the time-varying delay and the sampling instants have upper bound, the system is modeled as a hybrid system by employing hybrid system theory. Based on the model, considering the possible actuator failures, the existence conditions of guaranteed cost fault-tolerant control law is testified and the design for guaranteed cost fault-tolerant controller and the minimization guaranteed cost solution are presented in terms of the Lyapunov stability theory combined with Matrix Inequalities. Then, considering the system with parametrical uncertainties, the robust fault-tolerant controller method is studied. The robust fault-tolerant controller method and the maximum value of time-varying delays are given under the condition of the system with integrity. Furthermore, the robust H∞fault-tolerant controller method is also studied and a robust controller satisfying the H∞performance index is designed.