Modeling And Stability Analysis Of Networked Time Delay System

The feedback control system wherein control loops are closed through controlnetwork is called networked control system. Networked control system has theadvantages of less wires, high reliability, increased system agility and good flexibility,etc.. The medium of control network is time sharing multiplexing, so networkedcontrol system is affected by network induced time delay inevitably. This time delaycan be a dominant factor which degrades networked control system performance andmakes system unstable. Depending on the network protocol, the characteristics oftime delay can be constant or time-varying, which makes it hard to analyze and designnetworked control systems.This dissertation has studied several kinds of sampling technique and device nodedriven technique of networked control system, and has analyzed components ofnetwork induced time delay. Three kinds of control network time delay characteristicsand their performance has also been studied. On the basis of that, two discrete timemodels of multi-input and multi-output networked control system in which separablesensors and actuators are included are derived when actuators are time driven or eventdriven considering the effect of networked induced time delay using discrete timesystem theory.Based on the discrete time system model of networked control system, twosufficient conditions are obtained which guarantee the stability of networked controlsystem using discrete time system stability theory. One is maximum allowablenetwork induced time delay for α -stability and the other is the relation of networkinduced time delays which guarantees the poles of networked control system are inthe D (α ,r) area. Simulation experiments illustrate the effectiveness of the presentedtheory.This dissertation gives a detailed description of priciple of EDF(Earliest DeadlineFirst) scheduling strategy, and also studys the problem encountered when EDFscheduling strategy is introduced to network information scheduling and its solution.A EDF-MEP(Earliest Deadline First-Maximum induced node Error Prior) networkinformation scheduling strategy is derived to guarantee stability of networked controlsystem and enhance system performace. And an analysis of node error is alsopresented when EDF-MEP scheduling strategy is introduced to network informationscheduling.