Network Control System Fault Diagnosis Technology

With the development of the networked control technology, it has become a kind of new trend that the traditional control system is networked. Because of the complexity of network, networked control system (NCS) has higher level of demands for safety and reliability than general system. If some kinds of small faults aren't removed in time, it will probably bring enormous tragedy and loss. Therefore, the research on fault detection and diagnosis of networked control system has great theoretical and applied value.The FDD of NCS is studied in this dissertation. The main research works are concluded as follows:(1) The basic problems and the present research status of networked control system are systematically and comprehensively introduced. Besides that, when we think of network-induced delays and packet dropout, deferent mathematical models of NCS are set up.(2) According to the problem of networked control systems with random short time-delay and L₂ norm bounded disturbance, the design of observer-based robust fault detection filter for NCS can be formulated as a H_∞filtering problem, and be solved further by suitably selecting weighting matrix and observer gain matrix, which could maximize the sensitivity of residual to fault and simultaneously guarantee the robustness to random short time-delay as well as disturbance. Finally, FD of NCS is succeeded by the output residuals.(3) A memoryless reduced-order state observer is constructed according to the model of networked control systems with long time-delay. Then the residual is generated by comparing the state of the observer with the state of the practical system, and the stability of residual system is proved. In the end, FDD of NCS is realized by the output residuals.(4) FDD of NCS with random short time delay and data packet dropout is studied. Under fixed packet dropout rate, two state observers are designed corresponding to whether the data packets may be permitted to be transmitted or not. Then a residual equation is modeled as an asynchronous dynamical system with rate constraint on two events, and the condition for exponential stability of the systems is given. What is more, the fault detection and diagnosis of NCS is succeeded by the output residuals.