Fault Detection And Diagnosis Of Networked Control Systems

The fault detection and diagnosis (FDD) of the networked control systems (NCS) arestudied in this dissertation. The main research works are concluded as follows:(1) The definition and classification of the faults in control systems are discussed.The classification is based on the position, character and effect of the common faults,respectively. The faults of the NCS are modeled based on the position and the character ofthe faults, and the uniform model of the systems with actuator and sensor faults is given.(2) The fault detection of the NCS with short time delay and data packet dropoutis studied. The NCS with time-driven sensor node and controller node, event-drivenactuator node and short time delay is modeled as an uncertain discrete time system.Considering the NCS without data dropout, the fault observer is designed and the stabilitycondition is given based on Lyapunov stability theory. Considering the NCS with datadropout, under fixed packet dropout rate, the error equation is modeled as an asynchronousdynamical system, the fault detection is studied and the condition for exponential stabilityof the systems is given.(3) The robust fault detection and diagnosis of the NCS with long time delay arestudied. The sensor, controller and actuator nodes are all time-driven. Based on discretemodels, the problem is discussed supposing the NCS with output delay, control delay andboth output delay and control delay, respectively. For the NCS with output delay, theobserver with delay compensation is constructed. The error equation of the observer ismodeled as a switched system, and the stability condition of the error system is given. Forthe NCS with control delay, the fault detection problem is considered when the sensor andthe actuator nodes are synchronous or asynchronous. The fault observer is designed and thestability is proved. For the NCS with both output delay and control delay and disturbances,the robust H_∞fault detection is studied, and the robustness and sensitivity are analyzed.After the fault detection, the faults are isolated with directional residual method, and thefault diagnosis is accomplished.(4) The fault detection and diagnosis of the nonlinear networked control systemsare studied. For the NCS with affine nonlinear controlled object and output delay, using theconcept of the dominant subsystem in fuzzy models, the observer with delay compensationis designed based on local T-S fuzzy models, and the sufficient condition of globallyasymptotic stability is given. For the NCS with usual nonlinear controlled object and disturbances, the local fuzzy models are given. With both control delay and output delay,the residual generator is designed using fuzzy parity equation. The method of faultdetection and diagnosis is discussed, and the fully-decoupled condition and solving methodof the parity vectors are given.(5) The robust fault detection of the NCS with time delay and multi-packettransmission is studied. When the controller data is multi-packet transmission, the systemswithout delay and with control delay or output delay are analyzed, respectively. When thesensor data is multi-packet transmission, the system with both control delay and outputdelay is analyzed. The fault observer is designed based on the augment model, the uniformerror equation is given, and the fault detection is studied considering the differenttransmission manners of the data packet. When there are disturbances in the NCS, the H_∞fault observer is designed to ensure the robustness of the fault detection.