Robust Control For Networked Systems With Random Communication Delays

With the rapid development of the computer-controlled technology and computer networks technology, it has come true that having one or more control loops closed via a serial communication channel. Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems(NCSs). Integrating computer networks into control systems to replace the traditional point-to-point wiring has enormous advantages, including lower cost, reduced weigh and power, simple installation and maintenance, and higher reliability.The insertion of the communication network in the feedback control loop makes the analysis and design of a NCS complex. The first issue is the network-induced delay that occurs while exchanging data among nodes of networks connect to the shared medium. The transmission delays are often random and mostly longer than one sampling period. Secondly, Due to the bandwidth constraint of the network, network scheduling which appears when reasonably allocating the shared network resources. At the same time, data packet dropout may occur during data transmission. Because of the bandwidth constraint and capacity limit of data packet, one-packet transmissions and multiple-packet ones are inevitable. These problems not only degrade the performance of the control systems, even make the systems unstable. So the stability analysis and design of the networked control systems have gained more and more attention.This article introduce several problems about Networked Control Systems and we studies about the random delays.In this article,We use H∞control to study the random delays and analysis the stabilization and design the H∞controller.The three-tank system is viewed as our control plant. In the end,We give out the simulink results at different sampling time.The multi-vessels flow system is a typical object in the process control. It hasextremely widespread application background in the production. The three-tank system is a nonlinear control system with double input and double output, which simulate the multi-vessels flow system. In the article, the three-tank system is used to study the control algorithm. Firstly, we have modeled and linearized the system. Then we get the discrete model of three-tank system. At the same time, we introduce the hardware and the setup of Three-Tank system based networked control system.The network-induced delay occurs while exchanging data among sensor, controller and actuator through networks. The network-induced delays are inevitable, which are the major cause of the deterioration of system dynamic performance and potential system instability. Therefore, it is imperative to analyze the stability of NCS with network-induced delay. In Chapter 3, we have modeled control systems with network-induced delay. During the course, the delays are divided into two kinds: delays less than one sampling period and longer delays(longer than one sampling period). For delay less than one sampling period, one can always receive a control sampling in a single sampling period. However, this may not be true for longer delays. For longer delays, one may receive zero, one, or more than one control samples in a single sampling period. Then, we analyze their stability using stability region and hybrid system stability analysis technique and give the stability region of Three-Tank system.The second problem of this article is we introduce the H∞control for network control systems with random communication delays. We firstly explain the problem,then we analysis the stabilization of the system in this situation.Although networked control systems with random time-delays have been studied for a number of years, there are still some interesting problems that deserve further research. For example,most literature including our previous works has dealt with the sensor-to-controller delays only. Another important type of delays, controller-to-actuator delays have not been fully investigated. Also,in the presence of random networked delays,the H∞disturbance rejection performance has notreceived enough attention. It is, therefore,the intention of this note to study the H∞control problem for a class of networked control systems with both sensor-to- controller delays and controller-to-actuator delays.These random delay are modeled as a linear function of the stochastic variable satisfying Bernoulli random binary distribution. An observer-based controller is designed such that the closed-loop networked control systems is stochastically exponentially stable, and the prescribed H∞disturbance attenuation performance is achieved. An LMI approach is develop- ed to tackle the addressed problem, which can be sovled conveniently by Matlab LMI toolbox.In the end, we conclude this article and analysis the develop direction of networked control systems.