Markov Modeling, Analysis And Design Of Networked Control System

With the rapid development, popularization and increasingly perfect of thecomputer networks technology, the control system based on the high speedcommunication network, which is so called networked control system (NCS),has become one of the hot research task in current international control field.The research on NCS has important theoretical meanings and also NCS hasextensive application prospects. The NCS is a feedback control system whereinthe sensors,actuators and controllers as the network nodes connected throughthe computer network or fieldbus to accomplish the control tasks. Differentfrom the traditional control systems, the distinct characteristic of NCS is thatthe network communication is one of the important parts of the control system.Because of the network-induced time delay which is often uncertain andtime-varying, and the transmitted data error or data dropout, the NCS is nolonger a constant, maturity and certainty. Also because of the event-driven andtime-driven coexisted in NCS, so it is required new views and more sustainingtheories to the study on NCS, which brings forward newly challenge anddevelopment opportunity to the investigation of the control theory.This thesis systematically analyze the characteristics of networked controlsystem, network-induced time delays and network data packet dropout etc, andthe effects made onto the control performances, then propose newly designedmethods which solve the stability and robustness problems of the controlsystem brought by the network-induced time delays and the data packetdropout.Firstly, in terms of the network-induced time delays, the NCS designproblem with the delays less than one sample period (which can be called shortdelays) and the delays more than one sample period (that is long delays) arediscussed, respectively. Based on the network-induced delays' Markovcharacteristics, we propose the NCS Markov jump models, present thesufficient conditions for the stability of the NCS, and give the state feedbackcontroller and output feedback controller design methods. Furthermore,considering the NCS with the short delays and the exterior noise disturbance,the H ∞ robust controller design method is proposed, and the systems robuststability condition is given. Also the simulation examples are given to illustratethe effectiveness of the proposed methods.Secondly, network data packet dropout is another issue in NCS, which candegrade the system's performance and even can make the system instable. Soas for the NCS with data packet dropout and network-induced time delays, thispaper proposes a new modeling method. According to the controller updateinformation when the data packet lost, two different schemes are given: one isadopting the latest arrival data information at the previous sample time toupdate the controller, another is designing a data packet dropout compensator,using the compensator's data information to update the controller. In theproblem analysis, we first incorporate the delays into the system model,transform the network-induced delays' uncertainty into the system parameters'uncertainty, then considering data packet dropout, assuming it submit toMarkov property, set up the 2 state Markov packet dropout jump model. Basedon the linear system jump theory, we present the sufficient conditions for thestability of the two different closed NCS models, respectively. Also simulationexamples are given to illustrate the validity of the results.