Fault Detection For Networked Control Systems With Time Delays,Packet Dropouts And Multiple-packet Transmission

With the network control system being widely used in agriculture,industry,etc.,people's living standards have been greatly improved.However,the introduction of network also brings about new problems,which will affect the system and lead to system performance degradation or even instability.As the scale and complexity of the control system increase,people have higher requirements on the security and reliability of the system.Because once this kind of system malfunctions,if can not be timely checked and eliminated,it is likely to cause heavy casualties and property losses.Therefore,it is of great significance to study the fault detection of networked control system.In this thesis,fault detection of networked control systems with delay,packet loss and multi-packet transmission is studied.The effectiveness of the proposed method is verified by numerical simulation.Firstly,the fault detection problem is studied for networked control systems with time-varying delays.By designing an observer-based fault detection filter,the problem of fault detection is converted into_?filter solving problem.Based on Lyapunov stability theory,sufficient conditions for the existence of filters are obtained.A closed-loop control system is constructed and the stability of the system is analyzed by linear matrix inequality.Construct the threshold of the residual evaluation function and judge the occurrence of the fault through the fault detection logic.The simulation results illustrate the effectiveness of the proposed approach.Secondly,the problem of fault detection is studied for networked control systems with random packets loss and external interference.The packet dropouts are described by two different Bernoulli distributed sequences,an fault detection filter is designed.According to the Schur complement lemma and Lyapunov stability theory,the sufficient conditions for the mean square stability of the system are given,and the system achieve a certain disturbance rejection.For the system with fault signal,the value of residual evaluation function will exceed the threshold in a short time,and the fault is detected by this method.The simulation results illustrate the effectiveness of the proposed approach.Finally,the fault detection problem is studied for networked control systems with multi-packet transmission.Construct a fault detection filter and consider transmitting data between the sensor and the fault detection filter by means of multi-packet transmission.The closed-loop control system model was established,using Schur complement lemma and Lyapunov stability theory to give sufficient conditions for the asymptotic stability of fault detection systems.The stability of fault detection system is analyzed by using linear matrix inequalities.The simulation results illustrate the effectiveness of the proposed approach.