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Analysis And Control Of Networked Control Systems With Time-delay And Packet-dropout

Posted on:2009-02-10Degree:MasterType:Thesis
Country:ChinaCandidate:Q GaoFull Text:PDF
GTID:2178360245462809Subject:Operational Research and Cybernetics
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With the increasing complexity of control duty and architecture, the share between each components of systems, the sharp expansion of exchange information, and the development and wide application of computers, communication, sensors and networked technology, a new type distributed intelligent control system----networked control systems (NCSs) emerges as the times require. They are feedback control systems with control loops closed via special or universal communication network. Feedback channels are closed via network and information is exchanged and transmitted by network, which make the astriction of traditional link between point to point is cast off, the restriction of systems in the space is broken, the space of control activity is enlarged, the complexity of the systems and the cost of running and maintenance of the systems are both reduced. Long-distance remote operation, remote medicine, remote teaching, wireless network robot, some weapon systems, burgeoning fieldbus and control systems based upon the industry Ethernet are all belonged to the category of NCSs. Furthermore, NCSs have broad application foreground in the area of avigation and spaceflight and complex dangerous industry control.As the NCSs bring us so much advantage, they also bring new challenges to the control subject. All kinds of information in NCSs share the limited network resource via time division multiplexing way. The performance of NCSs is influenced by the packet transmitting rate, the length of the packet and the adoptive medium access control protocol in the network. Therefore, network-induced time delay, packet-dropout and packet-disorder will be inevitably brought into the control loop for the intervention of network, which make traditional research methods not be applied directly into NCSs, and new control theories and methods are cried for investigation.First of all, we summarize the research actuality of NCSs, and expatiate on some problems aroused by the intervention of network in NCSs, include the point driven form, data sampling, network-induced time delay, single-packet transmission and multiple-packet transmission, packet-dropout, packet-disorder and network scheduling.The characteristic of network-induced delay existents in the networked control systems is analyzed. The composing and the reason which arouses network-induced time delay in the networked control systems are expatiate, and the characteristic of time delay in different control networks are analyzed. Modeling of close-loop networked control systems is given for three type time delay in NCSs—certain time-delay, stochastic time-delay and time-varying time-delay. Especially, we relegate the stochastic time-delay and time-varying time-delay to uncertain portions of the systems, and model the close-loop NCSs as discrete-time uncertain systems.We analyze the reason why there is packet-dropout in the NCSs and the characteristic of the packet dropping, and then establish the model of close-loop NCSs for two type packet-loss processes in the NCSs—certain packet-dropout process and stochastic packet-loss process. Certain packet-loss process is modeled as a switch which is cut at certain rate, and the close-loop system is model as an asynchronous dynamical system with rate constraints on events. Two types of packet-loss processes are considered. One is the arbitrary packet-dropout process, the other is Markovian packet-dropout process. The modeling of NCSs with stochastic packet-dropout is given more universally.Modeling, stability analysis and controller design are done for the NCSs with both network-induced time delay and packet-dropout synchronously. For the NCSs with certain time-delay and certain packet-dropout process, the modeling of the close-loop system is given based on the state-feedback controller and dynamic output feedback controller, sufficient condition and controller design to maintain the stability of the whole systems are derived. Discrete-time uncertain systems are modeled for the NCSs with both time-variant delay and certain packet-dropout process, sufficient conditions and controller design to maintain the stability of the whole systems are given based on the theory of uncertain systems. Modeling of NCSs with time-delay (certain and time-variant) and stochastic packet-loss process is established, sufficient conditions and controller design to maintain the stability of the whole systems are derived. The acquired results have more universal significance.For NCSs whose states of the controlled plant are not fully measurable, we establish the modeling of NCSs with both time-delay and packet-dropout based on the remote estimator which can estimate states of the controlled plant to compose state feedback controller.
Keywords/Search Tags:networked control systems, network-induced delay, packet dropout, stability analysis, controller design, linear matrix inequality
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