The Study Of Robust Fault-tolerant Control For Networked Control Systems

Networked control system was a closed control system by a real time network,and the feature of the system was that the control loop of the feedback control system was built by the networked channel.Compared with the conventional control systems,the NCS had some primary advantages,such as:reducing system wiring,cutting the cost,sharing the information, ease of the system maintenance,extending,diagnosis.However,while the NCS brought lots of conveniences to us through exchanging data among devices connected to the shared medium,because of the limiting of the network band,the issues of unequal-distance sampling, packet dropout,and networked induced-delay brought new challenge to the conventional control theory.With the development of the computer and information technology,modern networked control system which had wide application in the industry had large scale,and it must have high reliability and safty,so fault-tolerant ability of the NCS was a intrinsic condition during the system operating.In a word,the study of fault-tolerant control in networked control system not only had theoretical value but also had strong practical value.The problem of faut-toleant control in the NCS was studied in this paper,which based on the time-delay model of the networked control system with networked induced-delay and adopted the Lyapunov stable theory,Linear Matrix Inequalities.Some work was done as following by adopting state feedback control law or time-delay state feedback control law.Firstly,the problem of robust integrity in the NCS was studied,and the problem studied three systems which are the NCS with uncertainty of time-delay,the NCS with uncertainties of time-delay and parameter,the NCS with uncertainty of disturb.Based on the time-delay model,the sufficient conditions for the NCS against actuar or sensor failures possessing robust integrity were given by adopting state feedback control law or time-delay feedback control law,and the corresponding design method of robust fault-tolerant controller was presented.Secondly,the problem of robust guaranteeing fault-tolerant control in the NCS was studied,the problem studied two systems which are the NCS with uncertainty of time-delay, the NCS with uncertainties of time-delay and parameter.Based on the time-delay model,the sufficient conditions for the NCS against actuar or sensor failures possessing robust guaranteeing fault-tolerant were given by adopting state feedback control law or time-delay feedback control law,and the corresponding design method of robust fault-tolerant controller was presented. Thirdly,the results of simulation demonstrated the effectiveness and feasibility of the presented method in this paper.Further more,when the number of actuator was equal to the number of the sensor in the same closed-loop systems,it showed that the robust fault tolerant controllers are equivalent in mathematics and exchangeable in practise.Lastly,on the one hand,when the NCS with control time-delay adopted the time-delay feedback control law,the system against the sensor or actuar failures had good performance. The results of simulation showed that with the time-delay becoming large the performance of the system would turn bad and the system cost would turn large.When the control time-delayτis similar to the system time-delay,the performance of the system would be better.When the control time-delay is similar to the system time-delay for the same NCS,the performance of the NCS by adopting the time-delay feedback control law was better than the performance of the NCS by adopting the feedback control law,however the constrains of the controller in the former was more than the later,which would make the space of solution become small.On the other hand,comparing the NCS with uncertainty of time-delay to the NCS with the uncertainty of time-delay and parameter,the robust fault tolerant controller in the later against sensor or actuator failure would have more constrains which would lead to the solver space turning small.