Research On Integrations Of Multi-fieldbus Devices Based On FDT-OPC

The presence and development of fieldbus has brought an involution in industry control field. With its digital, distributed and open character, fieldbus has been a hot issue in control field. The control system based on fieldbus is replacing traditional control system, and represents the orientation of advanced control system. However, the fieldbus is various in styles at present and applied widely in different fields individual. No kinds of filedbus can be totally suitable for all applications. Thus the situation that many kinds of fieldbus coexist will exist in a very long time. Various kinds of fieldbus products are unable to realize mutual operation and cooperating work because of difference of the protocol. In this way, it hinders users' choice seriously. Therefore multifieldbus integration already becomes the inevitable trend.Under the Microsoft's cooperation and the guiding of the OPC foundation, OLE (OLE for process control) was established as the interface standard of the automatic field by the leading manufacturers of the automatic field all over the world. It was based on COM/DCOM technology standard and designed for the information alteration of the process control software. With OPC standard is proposed, it provides an effective solution in the problem of multifieldbus integration. Through adopting OPC technology, every fieldbus can realize information sharing and seamless integration, as well as Plug & Play of fieldbus equipment. The mutual operation and adaptability of multifieldbus is enhanced greatly.Though OPC technology can be applied to solve the integration problem of multifieldbus control system, it needs to implement an OPC server for each different Fieldbus. The development of an OPC server must achieve the data exchange with field devices. Therefore, under multifieldbus control system, OPC developers should be familiar with the data acquiring methods of different field device and the protocols of different fieldbus. Therefore, the development of the OPC server cannot be independent of fieldbus types, and this leads to increase difficulty and time for the development of the OPC server.FDT (Field Device Tool) standard is proposed by ZVEI (German Electrical & Electronic Manufacturers' Association) and published by PROFIBUS in 2000. After FDT standard be published, it was quickly supported by several dozens of vendors, and set up a non-profit organization responsible for the FDT JIG in 2003,the organization aim to promote research and development of this technology, and the standard has become an international standard now. FDT standard defines the objects and interface of FDT frame application, and also defines interface between device DTMs (Device Type Manager) provided by manufacture and the engineering software of host system. By defined interfaces, the host system manufacture can integrate field device, independently of the type, manufacturer and fieldbus protocol.To solve the disadvantage of the method that used OPC technology to solve the problem of multifieldbus integration, this paper studies on the mechanisms or technology of FDT technology, which can integrate any field device independent of its fieldbus protocol, and puts forward a Development Model of OPC Data Access server based FDT technology, the model applies FDT Frame Application, device DTM , Nested Communication and other related technologies to access the field devices independent of fieldbus protocols. In this way, the model solves the problem that development of OPC servers is not independent of fieldbus protocols, device manufacture and device type. Finally, this paper provides the way of the implementation of development model and implements an OPC Data Access server that is necessary for using the development model for application in next step.