The Design Of Realtime Communication In Distributed Control System

DCS,named Distributed Control System,is a new kind of computer control system relativing to the concentrated system.It is developed and evolved from the concentrated system.Now,DCS is widely used in the electrical power ,chemical , petrochemistry area.DCS's framework is net,it is the base and core in the DCS System.Every manufacturer engaged in the design of the net because that the net playing the most important role in the Real-time,reliable,extendable system.In the DCS system,real time is needed,it means that the signals must be communicated in the limited time.The limited time means that ,in any case ,the signals must be communicated in the limited time that asked ,and the limited time is been designed by the control system's Real-time demand.But in the processing of the industry,there are many data in the communication,it also cause the delay problem in the communication.The net is also need to be reliable,because that ,in any case,the communication can not be interrupted,otherwise,it will cause the fatal accident.How to make the signals be communicated duly and safely and communicated effectively is an important topic in research.This paper involved in own designing DCS system.Some problems exposed in the processing of the design including how to combinate the components,the load and delay problem,software design,etc.In the problem of combinating the components,at first,this paper discuss the Ethernet,the archetype of the Industrial Ethernet,point the shortcoming in detail,and then discuss the envolved ethernet ,the Industrial Ethernet.This paper also discuss the experiment in delay of the Ethernet.The paper use some methods to void the load and delay problem, one method is that the net be divided into three sub net by the protocol and the function in use,another method is to reduce the request and response signals.In this method argues that singals be divided into several types and can use a kind of buffer module in the design. In software design, subscription can be used to reduce the data during communication,it is the best choice in the design of DCS.In the software structure,the paper use the standard OPC criterion to design,and describe the OPC criterion,OPC interface in detail.At last,there is an experiment in the communication of the OPC and proved that OPC is useable in the application.It is significative that in this paper, not only several methods are successfully put forward to solve the problems of the communication and safe,but also to be helpful in designing other system, in which lies the meaning of our work.