Analysis And Synthesis Of Networked Control Systems

With the rapid development of computer technology and network technology, together with the increasing scale of control system, the main feature of control system in 21st is involved with network. Networked control systems (NCSs) come into being by combination control technology with computer technology, communication technology and network technology, etc., wich can be applied in almost any distributed devices with controller requring data exchange. The appearance of NCSs manifest the developed trend of control systems, i.e. neworked, integrated, distributed and nodes intelligentized. NCSs are the new stage of current development of control systems. The enormous advantages of NCSs, including lower cost, reduced weight and power, simpler installation and maintenance, ease of system diagnosis, and increased system flexibility, etc., which have made NCSs increasingly popular in many real-time distributed control applications such as industrial automation, intelligent vehicle systems, mobile robotics, advance aircraft and spacecraft and national defence, etc.. However, the insertion of the network in the feedback control loop brings many new issues inevitably such as network-induced delay, data packet dropouts, multiple-packet transmission, clock synchronization, etc.. These issues can degrade the performance of control systems and can even destabilize the system, which make the analysis and design of NCSs complex. Therefore, analysis and synthesis 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.In the dissertation, some essential issues of NCSs are dicussed from the point of view on control theory and arithmetic. Modelling, stability analysis and control problems of NCSs are investigated based on some existing results of Lyapunov stability theory, time-delay system theory, stochastic system theory combined with linear matrix inequalities (LMIs) techniques, descriptor system approach and free weighting matrices approach. Some new results are given in the process of analysis and synthesis on NCSs.Firstly, the background, history, basic concepts and features of NCSs are introduced, and some essential issues of NCSs are presented in detail. From points of view on control and network communication, the main research contents and methods of NCSs at home and abroad are summarized comprehensively, and also the existing issues and contents to be studied are given.Since control network is one of the crucial parts of NCSs and network-induced delay is the essential issues in NCSs, consequently, the basic concepts and contents of control network are introduced. Much emphasis is put on the discussion and analysis for the characteristics and performance of three typical control networks, i.e., Ethernet, ControlNet and CAN Bus. At the same time, the time-delay issues, for example, the components, definition of delay and its impact on NCSs are analyzed detaily. These qualitative analysis and discussion have much important guidance and reference values in studying of modeling, stability analysis and control for NCSs.In view of previous results on modeling and analysis for NCSs are almost limited to single feedback control loop, a class of multiple time-delays NCSs and multi-input and multi-output (MIMO) NCSs continuous time models are proposed. Delay-dependent stability and stabilization of the NCSs with multiple time-delays are dealed with by utilizing the Lyapunov stability theory combinied with LMIs techniques. Some new less conservative stability and stabilization criteria in terms of generalized Lyapunov matrix equation (inequality) and LMIs are derived. Stabilizing controller via state feedback is formulated by solving a set of LMIs.Considering a class of MIMO NCSs with constant delays, time-varing delays and structured uncertainties, robust stability is investigated for the uncertain NCSs with multiple time-delays based on Lyapunov stability theory approach, LMIs techniques, descriptor system approach, and free weighting matrices approach, respectively. Some new delay-dependent / delay-independent stability criteria, delay-derivative-dependent / delay-derivative-free stability conditions in terms of LMIs are given, and the results of corresponding norminal systems are also presented. These propsed reuslts are much less conservative and are more general than the existing ones. Numerical examples and simulations are provided to illustrate the effectiveness of the proposed methods.For the NCSs with data packet dropouts and network-induced delay simultaneously, a model with structured uncertainties and exoteric disturbance is constructed, which is equivalent to an uncertain Markovian switching delayed system. By constructing a new Lyapunov-Krasovskii functional, delay-dependent robust stability, robust stabilization andΗ∞control with a prescribed disturbance attenuation level of the NCSs are investigated by combining Lyapunov stability theory, stochastic delayed system theory with LMIs techniques, descriptor system approach and free weighting matrices approach. A series of robustly stochastically stable and stabilizable criteria in terms of LMIs are obtained, which are much less conservative and more general than the existing ones. Also, the algorithms to get the maximum allowable delay bound (MADB) are given. Numerical examples and simulations show that the methods are effective.For the NCSs with potential stochastic perturbations, the problems of robust stability and exponential stability in the mean square for a class of uncertain linear and nonlinear stochastic systems with time-varying delay are investigated. Based on Lyapunov stability theory, stochastic delayed system theroy combined with LMIs techniques and some free weighting matrices approach, some less conservative robustly stochastically stable and exponentially stable in the mean square criteria in terms of LMIs are derived, which also hold for their corresponding deterministic systems with time-varying delay. Numerical examples and simulations are given to show that the proposed methods are more effective and are an improvement over previous ones.An experiment simulation platform for NCSs is developed. Some simulation experiments for the given systems on real network are realized on the platform, thus a comparatively better simulation environment for design and analysis of NCSs is provided. However, the plotform is just an elementary simulation software, much work leaves to be done to make it more perfect in subsequent research.Finally, a summary has been done for all discussion in the dissertation. The research works in further study are presented.