Research On The Modeling And Control Of Networked Control Systems

Networked control systems (NCSs) have been received much attention in recentlyyears. Compared with traditional point-to-point wiring connected control systems, themain advantages of NCSs include ease of installation and maintenance, facility of remoteoperation and control, low cost, high information sharing, etc. However, there are someproblems along with the insertion of communication networks in feedback control loops,such as network transmission delay, packet-loss and channel uncertainty, which will degradethe system performance or even cause the closed-loop instability. Based on existing resultson NCSs, this thesis mainly considers the modeling and control of discrete time NCSs withchannel uncertainty and packet loss. The main contents of this thesis can be summarizedas follows:Firstly, the existing researches on modeling and control methods of network controlsystems are introduced, and we also describe some typical networked control algorithms.All of this provide the theoretical basis for the further analysis, modeling and research ofnetworked control systems.Secondly, for the problems of the channel uncertainty and packet loss in the networkedcontrol systems, we give the mathematical expressions of channel uncertainty and packetloss respectively. Then a new model is proposed to describe the NCSs with both packetloss and channel uncertainty in an unifed framework and the closed-loop model of theNCSs is also given.Then, this thesis considers the problems of state feedback control for networked con-trol systems concerned both bounded arbitrary packet loss and channel uncertainty. Witha bounded deterministic packet loss model, such a closed-loop model of the NCSs is estab-lished combined with the mathematical model of the channel uncertainty proposed before.The stability conditions of networked control systems are given by a common quadraticLyapunov function approach. We also give an approach to design the feedback controllerbased on the Schur Complement lemma and the LMIs toolbox.At last, the problems of output feedback control for networked control systems con- cerned both bounded random packet loss and channel uncertainty are considered in thisthesis. The problems of state feedback control for networked control systems are discussedin the previous chapter, but state variables are not often all available in practical applica-tions, so the research of the output feedback strategy based on observer is necessary. Bymodelling the packet loss process as a Bernoulli distributed white sequence, the closed-loopmodel of such systems can be established. In order to deal with the stochastic parameternetworked control systems, we introduce the notion of stochastic stability in the meansquare sense. A new sufcient condition is proposed to guarantee the exponentially meansquare stability of closed-loop networked systems. Furthermore, by using the stabilitytheory, the controller and observer design problem is solved.