Study And Design Of Controllers And Communication Protocols For Networked Control Systems

With the development of automation and communication, networked control systems (NCS) are brought into use in industrial plants. Networks, which are normally called industrial control networks, improve the control properties such as reliability, economy, fixing, maintenance and system integration. In the same time, networks bring network-induced delay into NCS, which will decrease the control properties and even lead the NCS to instability. Design of the control systems with networks becomes a complex and hard work.There are two ways to analysis and design networked control systems. One is to design control algorithm beyond the existing industrial networks, and the other is to design industrial network based on the full-fledged control theory, which were both studied in this paper. Networks can be divided to two kinds: uncertain delay and certain delay NCS. Scheduling and design for two sorts NCSs were presented. In the other hand, a new design method of industrial Ethernet communication protocol based on TCP/IP was presented, including the design method and the design process. The main research works are concluded as follows:(1) For the certain delay NCS, the equivalent sample theory and its application in analysis of networked control system (NCS) were presented. After analyzing NCS's scheduling in master-slave mode, the theory of equivalent sample was presented, based on which the stability and design method of this kind of NCS were analyzed. For the uncertain delay NCS, scheduling, model, stability and control design were summarized. The controller designs of NCS with fuzzy PID, NN PID and Smith compensation PID were presented.(2) The design methods of field bus protocols with three different bus-control ways were shown. With the experiments of the communications, the performances of different protocols were compared.(3) Designs about the industrial networks protocol based on TCP/IP and UDP/IP were achieved. The performance evaluation methods of industrial networks were expressed, in which the real-time property is the most important performance. The experiments of the network response time were shown; whose results confirmed that protocol with UDP/IP was better in real-time property than protocol based on TCP/IP.(4) With analysis time delays about two sorts of networks, a new hardware-in-the-loop simulation device is introduced, and a new design method of NCS is presented. Firstly design the system based on average delay, and then simulate the system and choose the suitable parameters on the hardware-in-the-loop simulation. (5) Design of the intelligent sensor is an important job of the networked control system. The technologies of multiplex and cross-lays were applied in the model of TCP/IP, based on which the design method and process of intelligent sensor were presented.(6) Data relationships among networks were presented. The concept of data relationship was provided, and two kinds of data relationships, including from bottom to top and from top to bottom, were shown. An example named multi-point dehumidifier monitor system was shown, based on which the applyment method of data relationships was presented.