Stability Analysis Of Networked Control Systems

With the rapid development of the computer-controlled technology and computer networks technology, it has gained more and more attention that having one or more control loops closed via a serial communication channel. So it is called networked control systems (NCSs) where feedback control systems wherein the control loops are closed through a realtime network. Integrating computer networks into control systems to replace the traditional point-to-point wiring has enormous advantages, including lower cost, reduced weigh and power, simpler 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 the network connect to the shared medium. Next, the network can be viewed as a web of unreliable transmission paths. Some packets not only suffer transmission delay but, even worse, can be lost during transmission. Another issue is that the scheduling of the shared network resources.This thesis discusses a class of linear continuous system and presents the sufficient condition for the stability of the NCSs firstly. The result obtained can include information on size of the delay. The Razumikhin and Lyapunov theorems are employed to investigate the problem. Compared with the result of Walsh's, our result is less conservatism. Also the simulation results illustrate the effectiveness. Following this, based above conclusion, we study a class of linear continuous system with parameter uncertainties and a class of nonlinear system separately and present the sufficient condition for the stability of the NCSs. Also simulation examples are given to illustrate the effectiveness.Next, in NCSs, the performance (e.g. stability) of the control loops not only depends on the design of the control algorithms, but also relies on the scheduling of the shared network resources. In many real-time control systems, the rate monotonic (RM) and the earliest deadline first (EDF) scheduling algorithm are used in general to allocate the CPU resources. In the fifth chapter, we describe the problem in NCS scheduling in order to allocate the network resources.Then we construct the circumstance for the simulation by TrueTime software to schedule a class of NCSs and carry out schedulability analysis.In the end, we conclude this thesis and present the future work.