Analysis And Control Of Stochastic Networked Control Systems

With the rapid development of automation, the popularization and increasingly perfection of the computer networks technology, the control system based on the high speed communication network which is called networked control system (NCS) appears. The networked control system has become one of the hot research task in current international control field. Different from point-to-point connection, the important feature of such NCS is that sensors, actuators and controllers are all connected to the network as nodes. Because of exchanging data through the shared medium, the insert of network in the control system can inevitably bring the following problems:network-induced delay, dropping of network packets and single-packet or multiple-packet transmission of plant inputs and outputs. The presence of these problems not only can degrade the performance of control system but also can destabilize the system. Therefore, the study of networked control systems has important significance of practice.Based on the stochastic Lyapunov stability theory, in term of linear matrix inequality (LMI), this paper proposes analysis and synthesis methods for the networked control systems with random delays and random packet dropout by designed new controllers and observers. This paper is organized as follows.Firstly, the background and important significance in research of NCS are expatiated. Some basic problems and recent advances in research are discussed in detail. This article has studied several kinds of sampling techniques and device node driven techniques of networked control systems, and analyzed network-induced time delays and network data packet dropout.Secondly, random network-induced time delays have been described in two forms. Then two discrete time models of the NCS with random delays are derived. On the one hand, the random delays are modeled as a linear function of the stochastic variable satisfying Bernoulli random binary distribution, sufficient conditions for the stability of the NCS have been presented, and a responding controller has been designed. Simulation results have demonstrated the feasibility of the control methods. On the other hand, by modeling the random delays as Markov chains, necessary and sufficient conditions of stability for the NCS are obtained and a numerical example has been considered to illustrate the main results.Thirdly, this thesis has studied the NCS with random packet dropout. An iterative approach is proposed to model the NCS, sufficient conditions for the stability of the NCS have been presented, and a state feedback controller has been designed. A simulation example is worked out to illustrate the effectiveness of the results.Finally, the research conclusions are presented. The innovative ideas and the remaining problems of networked control systems need further research.