The Research And Application Of OPC Client's Development

OPC is the generic OLE for Process Control, literally translated as the Object Linking and Embedding technology in process control. OPC specification is an open and interoperable software interface standards in the field of process control, based on the functions required by Microsoft's COM (Component Object Model) and DCOM (Distributed Component Object Model) technology. Today, in the field of process control, it is a very popular data exchange technology and the middleware technology that realizes information exchange between open system field equipment in control system and process management level, and lets the control system to be an open system.OPC specification uses Client/Server mode, and defines the standard interface between OPC Client between OPC Server. In the OPC Server end, the control equipment manufacturers package the hardware device drivers and the communication program to be an independent OPC server providing real-time data to OPC Client. The OPC Client developed by customers who use the equipment is able to obtain data from the OPC server as long as following the OPC data interface protocol, also it may include no communication interface program, does not have to care about the hardware characteristics of the bottom, has no need to consider how to communicate between hardware and software. Thus it realizes the integration of flexible configuration of a variety of data and multi-system. Because the OPC Server and Client interface is the standard, it can develop a universal OPC Client that different applications with a visit to the same equipment or applications with a visit to different devices.First, the paper introduces the background of OPC technology as well as its main characteristics and development, analyzes its core technology of COM/DCOM. Then, the paper studies the OPC Data Access specification and the communication mechanism between OPC client and server, introduces how to develop client program using the Visual C++. This is the core of this thesis. OPC Client Development resolved multithreaded programming, OPC interface and multi-view display technology problem, completed an OPC DA norms source-level development work. And fully consider the difference between latest OPC DA 3.0 version and the old version 2.0, designed to be compatible with the new and old versions of the client software. Achieved to connect multiple OPC server for data collection and functions of management and maintenance. Finally, introduces the testing procedures of OPC client. The testing results show that the OPC client has a good safety and reliability, and can access data from server stably and effectively. We apply OPC technology to design and develop the project of "the detection and control system of the abnormity in steel mill blast furnace". The performance of data collection system based on OPC technology in the field of control is more efficient.Shortly, the studies and practice of the task provides a good reference to understand the internal mechanisms and develop OPC Client application, accelerate the development of modern information control systems based on OPC-based middleware technology.