The Research And Application Of OPC Technology For Distributed Control System

With the development of the computer, micro-electronics and network technology, the industry control field has deeply changed. The new distributed process control system has builduped, from the bottom to the top is factory intelligent control, industry process control and business applications in turn. Intelligent instruments are widely use in industry field,providing plenty of information which cann't gained before,the integration is necessary to make the information transfer in each level.At the same time, the information complete sharing needs more and more, therefore, the requirement to the opening of the industry control system is higher and higher. However, traditional control systems such as Distributed Control System (DCS) and Fieldbus Control System (FCS) are comprehensively implemented in industry. But, it is difficult to interconnect and interoperate with other control systems or instruments produced by other companies, due to the reason that the traditional control system adopted custom-defined special communication networks and particular communication protocols that lack standard interface to other control systems. Thus, each control system is unique in its style, which forms "information isolated island". With the appearance of Ethernet and OPC (OLE for Process Control) technology in network and interface, it is possible to realize system integration between DCS and FCS. According to actual requests, this paper research the complete integration system based on OPC technology, and Ethernet.Firstly, The method of network integration use Ethernet amang plenty of Field Bus are analyzed,and the three treatments of interface integration: DDE, ODBC and OPC are analyzed and compared. The advantage of OPC has been pointed out. And, design the compelte integration system based on OPC based on OPC technology and Ethernet.Secondly, the OPC DA (Data Access Standard) has deeply pointed out, based on the analysis of COM/DCOM technique.The custom and automation interface are analyzed and compared, and the method of compile OPC client with custom and automation interface are compared, the three method of data access are compared, The main methods and the steps of designing OPC client program based on OPC Data Access Automation Interface Specification are given. And the OPCclient program is implemented with Visual Basic.Finally, based on the control requirement of Supervisory Control system of Geotextiles-laying Vessel, a Supervisory Control system of Geotextiles-laying Vessel based on the OPC and Ethernet was designed, compile the Ethernet communicate program, configure the OPC server, exploit a OPC client program to realize the data exchange of OPC server, achieve the Ethernet communicate of Geotextiles-laying Vessel Supervisory Control system and PLC system by the testing of run and use on vessel, shows that the system has a simpleness configuration of Supervisory Control system, has good real-time performance of data exchange and good dependability, and convenient for the system to upgrade and spread.