H_? Filtering Approach To Networked Control Systems With Limited Communication Via Delta Operator

Networked Control Systems(NCSs)are combination of communication technology,network technology and computer technology.Compared with the conventional point-to-point transmission,NCSs have the advantages of easy maintenance,high reliability,low cost,and resource sharing.However,due to the insertion of the network,there will be induced limited communication,packet dropout,and random time delay at the same time.The features of system could be reflected by different filters.The H_? filtering has become the preferred filtering for NCSs because of its good robustness.The discrete systems and the continuous systems are usually discussed separately.The delta operator approach can avoid the problem of instability boundary aroused from the traditional shift operator model with high-speed sampling.And the delta operator method could put both discrete and continuous system models into a unified frame.In conclusion,the study of filtering for NCSs with limited communication using delta operator has great significance.The thesis is supported by the National Science Foundation of China “A unified approach to fault detection and filtering for networked systems with high-speed sampling”.This thesis concentrates on the filtering problem for NCSs with limited communication via delta operator,including the H_? filtering for NCSs with packet dropout,the H_? filtering for uncertain systems,the H_? filtering for NCSs with random time delay.Different system models are established and analyzed.The major contributions of the thesis are concluded as follows:Firstly,focusing on the phenomenon of packet dropout and limited communication,the filtering of NCSs based on delta operator are addressed.The packet loss and the limited communication of NCSs are modeled as a Markov chain and a communication sequence respectively.The model of NCSs is constructed by delta operator,as well as,the filtering error system is established.A sufficient condition for the stability of filtering error system is obtained in terms of LMIs.The explicit expression of the desired filter is also derived.A numerical example shows the feasibility of the method.Then the H_? filtering of uncertain NCSs with limited communication is discussed.The parameter uncertainty of NCSs and the filtering error system are considered by using delta operator.The asymptotic stability of filtering error system is proposed by constructing a suitable Lyapunov functional.The H_? performance index is obtained in terms of LMIs,and the gains of filter are also obtained.Finally,the H_? filtering problem of NCSs with random time delay and limited communication is studied.The random time delay and the communication constraint of NCSs are described as a Bernoulli random variable and a communication sequence respectively.Based on the established Delta operator model,the filtering error system of NCSs is obtained.A sufficient condition for the stability of the system is deduced by Lyapunov functional.An H_? filter is designed by using LMIs technology and the gains of filter are also got.A numerical example shows the effectiveness of the method.