Analysis, Modeling, And Control Of NCS

Networked control system (NCS) is objectively needed by complicated control systems and remote control systems. Compared with the traditional point-to-point control systems, NCS has enormous advantages such as the shared resources of information, reduced system wiring, easy of system extending and maintenance, higher reliability and flexibility, and so on. However, because of the constraints of the communication bandwidth, the problems of network-deduced delays, packets dropout, and multiple-packet transmission are unavoidable, which degrade the performance of control systems and even make them unstable. Considering these problems, this dissertation studies the modeling and control of NCS.First, the factors affecting the performance of NCS are presented. The different characters of communication networks, the reasons why delays happen, the compositions of delays, and the influences of the network-deduced delays and packets loss to system stability are analyzed.Next, the augmented controlled plants including networks are analyzed and modeled in this dissertation, based on the linear time-invariant industrial controlled plants. The two situations of single-packet transmission and multiple-packet transmission are introduced respectively, and different properties of networks are considered in each situation. The control systems including networks are time-varying systems, and there are different models for different networked properties. A uniformed model is developed in this dissertation, which makes for the analysis and design of the controller.Finally, on the basis of the uniformed model, state observer and control law are both designed using pole-placement. The full-dimension state observer and reduced-dimension state observer are developed respectively. The control law is time-varying linear state feedback. The separation principle is proved on the basis of the control law proposed in this dissertation. Furthermore, the stability analysis of the time-varying model is presented. The simulation results show that the control strategy proposed is effective.