Research On Some Issues Arisen In Networked Control Systems

Control systems in 21st century are combined systems of control and network. The research on Networked Control Systems (NCSs) has become very much a pioneering issue in the field of automation. Based on a review and analysis of its current condition and development home and abroad, the thesis systematically expounds some research results in theory and methodology of some basic but important issues on NCSs. The insertion of the communication network that is viewed as part of control system has greatly expanded the techniques and methods of industrial control. It has brought significant changes to automatic control systems and industrial control systems in systematic constructions, control method and man-machine cooperation approach, as well as some new issues such as coupling of control and communication,distributed control manners. The appearance of these new issues calls for the innovations and extension in control method and algorithm continuously under networked constructions.First,we briefly introduce the origin,developments,characteristics and current condition of NCSs.We also analyze the basic issues and typically research methods in NCSs detaily as well as our own views on the related reaearches.We present a periodic NCS model and the information-scheduling model in NCSs based on sampled data technique under communication constraints and varying sampling rates. Then, we discuss the asymptotically stable problem of networked control systems under above conditions. The admissibility problem of such information scheduling approach is tested through the stability justification of the closed-loop NCS under certain given sampling manner. The LQ guaranteed cost control problem and disturbance rejection problem are also discussed.In order to avoid droping out,congestion as possible and to improve the utilization of the network under limited resources, we decrease the quantity of information transmitted in the network through periodic information scheduling method. In the same time, we design a series of dynamic output feedback controllers to keep the closed loop NCS asymptically stable and certain level of performance (LQ guaranteed cost control performance, H∞ disturbance attenuation performance). We also consider the system stability analysis and control design problem under varying sampling rate and sampled-data technique.Following that, we study the problems of system stochastic stability and H2/ H∞ mixed control based on the mathematics model of NCS with multistep stochastic transfer delay. It has been proved that the transfer delay can be viewed as a Markov process under certain communication control model. Then, we translate the whole system into a generalized discrete-time system with random jumping parameters. We formulate the H∞ control problem and mixed H2/H∞ state feedback design for obtained generalized system, and give some examples of how such design processes are carried out.In this section, we also consider the design problem of NCSs with multistep asynchronous transfer delay, which is another important issue in the research of networked control. The LQG control design process for NCSs with asynchronous transfer delay in different channels is obtained through the transformation of the system estimation model as well as multistep predictions of the state values.Next, we study minimization problem of queuing time delay in network and signal quantization errors in control system based on average behavior of network rate. Under fixed routing scheme and certain optimization performance indexes, both problems can be translated into convex optimization problems on limited communication resources allocation. And we obtain the solutions of the convex optimization problems through optimized allocation of communication resources such as network flow rate, transmission power and bit rate among network links.We also formulate a performance index on information transfer delay under certain condition when we stand on the point of control system design.And the detail design process on abov...