Research On Modeling And Control Of Discrete Networked Control Systems

With the rapid development of communication technology and the networking of control systems, the traditional point-to-point control strategy can not meet the performance requirements of control systems. Point-to-point structure in many occasions has been gradually replaced by communication networks and Networked Control System(NCS) in which sensors, controllers, actuators and other components connected through the communication network thus generated. Compared with the traditional point-to-point structure, NCS has many advantages such as lower wiring costs, easy diagnosis and maintenance, increased system reliability, so NCS has received wide attention in the aviation, aerospace, military, medical, industrial and transportation fields. However, the introduction of network in feedback loops makes the analysis and design of NCS more complex. Network-induced delay, packet loss, multiple-packet transmission, networked jitter, packets disorder and other issues make the system performance degraded or even unstable. Therefore, the research of NCS has important theoretical significance and practical value.In this paper, both the single-packet transmission and multi-packet transmission are considered, and the research concentrates on the modeling, control and fault detection of the NCS. Networked control system test platform is designed and implemented based on robots. The main contents are as follows:In Chapter 1, the concept of NCS and production process are introduced, and three basic structures of the system are described, then a number of fundamental issues of the system are discussed and the research status at home and abroad in this field is introduced. Finally, we outline the main contents of this paper.In Chapter 2, with the discrete NCS in single-packet transmission considered, the problems of modeling, stability analysis, robust H∞control and robust l 2? l∞control of the system with arbitrary time-varying delay and packet loss are discussed. For the NCS with network-induced delay and packet loss, the universal model of the discrete system is established. First, we discuss the stability and control of the discrete NCS without disturbance based on this model. Networked-induced delay is time-varying and it can be set to any of more than one sampling cycle. Then we introduce the external disturbance into the system and discuss the problem of robust control and robust control. Sufficient conditions to asymptotic stabilize the system and meet the requirements of the given robust H∞l 2?l∞H∞performance index and robust l 2?l∞performance index are derived. Algorithms to solve the maximum delay as well as , disturbance attenuation are presented. To optimize results, dichotomy is used in the iterate algorithm to solve the disturbance attenuation. As conditions in the presence of nonlinear term make it difficult to solve the matrix inequalities, cone complementarity linearization method is used to solve the controller. H∞l 2?l∞In Chapter 3, with the discrete NCS in multiple-packet transmission considered, modeling, stability analysis and robust H∞control of the system with arbitrary short time-varying delay and packet loss are discussed. For the discrete NCS in multiple-packet transmission, packet loss and arbitrary short time-varying delay, the universal model of the discrete system is established. First, the discrete NCS in multiple-packet transmission and packet loss is modeled as an asynchronous dynamical system(ADS) in both case of with and without arbitrary short time-varying delay. Sufficient conditions to asymptotic stabilize the system are derived and the algrithm to solve the controller is presented. Then the discrete NCS with packet loss, multiple-packet transmission, and arbitrary short time-varying delay is modeled as a discrete linear switched system with arbitrary switching signal in both case of with and without external disturbance. Stability analysis and robust control of the system are discussed combined with switching Lyapunov functions. H∞In Chapter 4, the problem of robust fault detection of the discrete NCS is discussed in both case of single-packet and multiple-packet transmission. First, a fault detection filter is designed for the NCS with short time-varying delay and norm bounded unknown input in the case of single-packet transmission. The problem of filter design is finally transformed into a class of the convex optimization problem with linear matrix inequalities constraints and objective function. Then the discrete NCS with both packet loss and multiple-packet transmission is considered and the error system is equivalent to discrete linear switched system by the characteristic of the multiple-packet transmission and packet loss. Sufficient conditions to asymptotically stablize the error system with H∞performance indexγand arbitrary switching signals are derived by the theory of switched systems.In Chapter 5, networked control control test platform is built with the AS-R type robot producted by Shanghai Grandar Robotics Co., LTD chosen as the plant to implement robot obstacle avoidance as an example. The platform provides test environment to verify the algorithm of NCS. The overall system is divided into two parts: the vision subsystem and the control subsystem, and the process of system design and network interface design of the two subsystems are given in details.