Analysis And Synthesis Of Networked Stochastic Control System

With the rapid development of network technology, more and more control systems adopt communication network to realize close-loop control, which means information exchange and control signal transmission among components are completed by communication network. This is the research object in this dissertation—networked control system. In engineering applications and practice, the insertion of communication network in the feedback control loop causes some indeterminate factors among which network-induce time delay mainly affects the system. In networked control system, time delay is stochastic and complex. In general, it is longer than one sampling period. Multi-step time delay can degrade the performance of control system and even destabilize the system, which gets the control of networked control system difficult in engineering application and will probably bring about enormous economic loss. Therefore, it is of great theoretical and applicable significance to research control analysis and synthetic problems. In this dissertation, these problems are deeply studied, and some new methods are presented to perfectly solve these problems, such as establishing models, the stochastic characteristics of multi-step time delay, optimal state estimate, synthetic control analysis, stability analysis, etc.In this dissertation, the present research situation of networked control system is extensively introduced. The internal and international research results, thoughts and methods of stochastic control and analysis are summarized. Then both theoretical results are combined, and suitable research approaches for stochastic networked control system with multi-step time delay are obtained. Two kinds of new control mode are presented, under which the system can make full use of control information. With the different driven modes of sensor, controller and actuator, four different mathematical models are established.According to different models, based on Markov chain theory, the stochastic characteristics and upper bound of time delay are discussed. New results of Markov transition matrix of two new control modes are presented. A new method to obtain maximum allowable delay bound is developed for stochastic networked control system with multi-step delay. An online evaluation method for networked control system with unknown probability distribution and bound is also introduced.Several typical approaches are adopted to realize the control analysis of stochastic networked control system with multi-step delay, including LQG optimal control method, infinite horizon optimal control method, finite moving horizon optimal control method, model predictive control method and time-varying delay compensation method. The model predictive control method is especially introduced to deal with vacant sampling and data rejection in networked control system. The stability analysis of control approaches above is also discussed. For networked control system with partial state information, the optimal state estimate is investigated. The optimal state estimator and controller are designed, which is presented in separation theorem.On the basis of various control analysis approaches above, a novel switching control method based onα-Credibility is provided. The controller of networked control system switches different control law to control the system according to time delay in different credibility intervals. The switching approach can improve the performance of networked control system. Computer networked control system based on intelligent agent technology to realize switching control method based onα-Credibility is presented, and the reliability of the system is discussed.