OPC Technology Research And Application In The PROFIBUS System

With the rapid development of technologies of computer, data communication and control automation, FCS(fieldbus control system) technology is more and more applied in industry control system because of its simpleness in structure and easiness in maintain and high reliability and openness. FCS is a new generation of control system after DCS, it represents an unreversed developing direction that digital devices, network devices,control functions,devices management are used in local machines.OPC (OLE for Process Control), wich is based on Microsoft' s OLE (object linking and embedding) /COM technologies,is an industry specification and standard generated to settle the communication problem between industry client computer and virous equipment drivers . OPC technology specification is established by OPC foundation, it provides an unitive data accessing software and hardware interface standard which has been accepted and supported by more and more software and hardware manufacturers and has become an acknowledged standard in industry control fieldbus. By using industry fieldbus based on PROFIBUS protocol as the reseach object, the author present the systen control solution, which adopts ope technology.This paper first explains the characteristic of the PROFIBUS technology, then introduces the basic conception, content and advantage of OPC, which came from COM', and also explains the basic principle of COM. The details about how the OPC user application program designed and developed are described in this paper. Because of the importance of data transfer, this paper anlyzes and explains the mechanism of three methods of data tansfer by turn. They are synchronization, asynchronism and subscription mechanism.At last, the development process of the monitor software of the supervisory computer based on OPC technology is introduced , and the modularized is adopted. The functional modules is also intrduced. The supervisory computer communicates with the subjacent computerthrough SIEMENS communication card CP5613. The supervisory computer can get the data from the production process.The system has several features ".using SIEMENS S7-300 series PLC produces as the subjacent computer, adopting Microsoft' s windows 2000 server as supervisory computer operating system. Adopting SIEMENS SIMANTIC STEP7 and Borland DELPHI 6. 0 as the developing languageAfter the hardware component and the software component of the supervisory control system are designed ,the basic functions, such as add item, read item . write item , can be realized. At the end of the paper, the demo of this supervisory control system show us the operating results.