Research On Time Delay Fault Diagnosis Method Of Networked Control System

With the rapid development of network technology,industrial production has stepped into the era of network and intelligence.Networked Control System(NCS)has been widely used in industrial production.NCS realizes the remote control between nodes through the network,and the communication network directly affects the stability of NCS.Therefore,it is necessary to diagnose the fault of NCS and adopt appropriate solutions to the fault in time.Taking NCS as the controlled object and focusing on the analysis and research of delay fault in NCS,two solutions are proposed to diagnose the short-time delay fault and long-time delay fault respectively.The feasibility of the two methods is proved by simulation experiments.The delay compensation strategy is proposed for the delay fault in NCS.Firstly,the purpose and significance of NCS research,system structure,common methods of fault diagnosis and research status of NCS delay fault are introduced.Secondly,the effects of delay,packet loss,network type,interference and network scheduling on the performance of NCS system are studied,and the impact of network delay is analyzed.Then,for the short-time delay NCS,the observer fault diagnosis method is studied.The mathematical model based on observer is established to analyze its model and design state observer.Based on the stability of the system,according to the residual error between the state output of the observer and the actual output of the NCS and the set threshold comparison,the fault diagnosis logic of the NCS is used to judge the fault situation.Then,for the long time delay NCS,the neural network fault diagnosis method is studied.On the basis of the observer diagnosis method,the neural network predictor is added between the sensor and the controller.And Genetic Algorithm(GA)is used to optimize the weights and thresholds of Elman neural network.After the observer error equation is stable,the designed observer can better track the system state in real time and realize state feedback.According to the residual generated by the designed observer and the set threshold comparison,the fault diagnosis logic of NCS can judge the fault situation.Finally,the delay compensation strategy is proposed.On the basis of GPC and in order to reduce the on-line time,the implicit GPC is proposed.In order to achieve optimal compensation,an implicit PIGPC with PI feedback structure is proposed.The delay is predicted by GA-Elman neural network,and the controller parameters are predicted by the predicted value instead of the real value.The proposed delay compensation strategy can compensate the delay and reduce the impact of delay fault on NCS by simulation results...