Research On Fault Detection Of Network Control System Based On Observer

Networked Control systems(NCSs) refers that the closed-loop feedback control system in which the target is connected with sensors, controllers and actuators through communication network. It has a relatively independent and well interconnected communication mode; that has been widely used in industrial control, production, aerospace,national defense and military and many other areas. But the uncertain factors it has, such as the limitation of network bandwidth; existing in the network environment, the sudden failure and the instability of network increase the system failure rate, whereas the fault detection technology provides important guarantee for the security and reliability of the system.Targeted at control system, concerning the introduction of the network control system in the presence of some of the basic issues, this thesis establishes a new closed-loop control system, a residual generator configured to generate a residual signal, a discrete-time fault detection model and design fault detection filter and controller to improve the detection of system fault and the stability of the system. Residual signal generated by residual generator not only has good robustness to external disturbances and some problems existing in the network(time delay, packet dropouts, etc.), but also has sensitivity for fault signals. It can quickly detect the fault. The simulation example is given to verify the effectiveness of the proposed methods in this paper. The research contents are as follows in this thesis:1. For a robust H_∞fault detection problem that has network-induced delay, random packet dropout, communication constraints and norm-bounded unknown input. Firstly, a robust H_∞fault detection filter design based on state estimate is proposed; then, the residual generator design is given based on a full-order filter with numerical example proves that the fault detection filter has good robustness to the external disturbances and other unknown input signals. Residual evaluation function can quickly surpass the threshold set by the system failure, detect the fault in the external interference.2. Researched a class of H_∞robust fault detection problem of NCSs with variable sampling period, a new closed-loop system model is established, the sampling period switching-based approach(the sampling period switches in a finite set) and the parameter uncertainty-based approach are proposed to deal with time-varying sampling periods.Considering time-delay exist in the channels between sensors to controllers and controllersto actors and the multi-packet transmission in the channels between sensors to controllers individually. The sufficient conditions for the asymptotic stability of fault detection system are given as well as the design methods of controller and fault detection filter.3. Considering a class of continuous NCSs with un-certain time delay and random packet dropouts, this paper merge the two networks S-C and C-A together for analysis,taking into account the presence of the packet dropouts in both of them, establishes discretization model. The robust fault detection filter and controller are also designed based on the observer which supplies sufficient conditions for the asymptotic stability of fault detection system.