Research On Fault Diagnosis For Network Control Systems

The research of fault diagnosis for Network Control Systems is becoming moreof a concern for the related scholars.But it is very difficult for the fault diagnosis ofNCS because of the network associated with some inevitable factors such as networkdelay、data packet dropout、timing error and so on.The existing research about faultdiagnosis for Network Control System is only considering network delay or datapacket dropout.In this paper,not only the network delay and data packet dropout areconsidered but also the classical fault diagnosis method baesd on model combining tothe intelligent fault diagnosis method are used to diagnose the system’s fault.Inaddition,the paper also studys fault diagnosis for Nonlinear NCS.Firstly,for a NCS with random short delay and data packet dropout,an stateobserver is designed firstly in this paper to obtain an state estimation error equationwhich is equivalent to an asynchronous dynamical system having event incidenceconstraint.Secondly,SVM is used to identify interferences of the NCS. Finally,makingthe identification result as compensation term adding to the state observer can makethe residual only represent fault term under ideal condition and increase therobustness of NCS for interference,which can improve the fault diagnosisprecision.The simulation results prove that the designed observer can diagnose faultseffectly and the disturbance compensation based on SVM has attained the expectedeffect.Secondly,fault diagnosis methods are researched in this paper according to aNCS with long-time delay and data packet loss.An state observer is structured tomake the state estimation error equation equivalent to an asynchronous dynamicalsystem having event incidence constraint according to whether the system having datapackets loss.The problem of fault diagnosis is converted to H filtering problemthrough structuring filtering residual system based on the observer,then giving acorresponding filter designing algorithm.The designed fault diagnosis filter systemmake the residual system’s H norm less than given reduction level.Finally,thesimulation results prove that the algorithm can diagnose faults effectively.Thirdly,the methods of fault diagnosis for Nonlinear NCS are studied in thispaper.According to a NCS with data packets loss from sensor to controller and modeluncertainty,a method of fault diagnosis is researched.First,fault diagnosis filter is designed as an error generator based on the state observer.Then construct rightLyapunov function,giving the sufficient conditions of system’s stability.Finally,thesimulation results prove that the algorithm can diagnose faults effectively.Finally,the effects generated by network’s characteristics such as networktime-delay and data packets loss and so on are studied in this paper using Truetimeand Simulink.Then fault diagnosis ia researched by Lssvm.