Modeling And Control Of Networked Control Systems With Packet Dropouts And Packet Disordering

NCSs are feedback control systems, wherein the sensors, actuators and controllers are connected as the network nodes through the computer network or fieldbus to accomplish the control tasks. In contrast to the traditional control systems, networked control systems have many advantages such as resource sharing, long-distance operation, less time and easy maintenance, etc. Communication networks have been increasingly employed to exchange information and control signals in modern industry and business fields, and networked control systems have played an important role and increasingly become a hot research topic. However, due to the insertion of the network, it is inevitable that network-induced delay, packet dropout, packet disordering and other unexpected facts exist in NCSs, which will inevitably degrade performance of the control systems or even make the control systems unstable, such that the analysis and design of the control systems become complex and the new challenges to networked control systems have arisen. Therefore, modeling and control of NCSs have become one of the most important issues in control theories study, and also have received considerable attention and interest by researchers in recent years.Packet disordering and packet dropouts are common phenomenon in modern industry and commercial networking application. In networked systems of Internet, the IP layer provides the non-guaranteed packet transmitting service in multi-routing transmission, so abnormal phenomenon such as packet dropouts or packet disordering is inevitable. Therefore, it is necessary to study the problem of packet disordering in NCSs.Recently, a wide range of research has been reported dealing with problems related to the network-induced delay and packet dropout. However, packet disordering-based analysis and control have not been fully investigated to date. In this thesis, a new mathematical model of NCSs is proposed, which can fully describe the phenomenon of packet dropouts and packet disordering in NCSs and effectively eliminate the impact of packet dropouts and packet disordering on the performance of NCSs.Firstly, in terms of data packet dropouts, the modeling and control problems of NCSs with discrete-time plant are investigated, based on the Markovian characteristics of the data packet dropouts, the definition of "the quantity of continuous packet dropouts" is given, and is described as a Markov chain, then the Markov jump model of NCSs is set. Considering the convenience, the global vector is introduced, thereby transforming the system model into the closed-loop Markovian jump linear system in which the controller depends on the mode characterized by Markov chain. Further more, the stability of the closed-loop system is discussed; and an LMI method is given for the controller design. Finally, a numerical example is given to illustrate the effectiveness of the method.Secondly, the model of NCSs with discrete-time plant is proposed, then the definition of "the quantity of continuous packet-disordering" is given, the random network-induced time delay and the quantity of continuous packet-disordering are described as two independent Markov chains. Then the global vector is introduced, and the obtained closed-loop systems are jump linear systems with two modes characterized by two Markov chains. Furthermore, the stability of the closed-loop system is investigated; and an LMI method is given for the controller design.