Studies On Implementation And Application Of OPC Technology In Modbus-TCP Industrial Ethernet Control System

At present, Ethernet technology has been widely accepted by industrial customers and begins to be used in field device layers of control systems. Among existent Industrial Ethernet systems, Modbus-TCP has step by step become a standard for industrial communication via Ethernet as a result of its open, easy-to-understand and stable specification, readily available base technology and the wide ranges of devices which are already available.To access field data, software manufacturers must develop a special driver for each given device during the process of developing traditional control system software. Then a lot of problems are produced such as repeated development, bad compatibility brought by different drivers, bad adaptability of drivers after updating the hardware, access violation when accessing the same hardware using multi-drivers, etc. With the publishing of OPC (OLE for Process Technology) technology, these problems have been perfectly resolved. Basing on COM/DCOM technology and adopting Client/Server mode, OPC specifications define a group of COM objects and interfaces to realize standardization of interfaces for reading data from the field. Thus, the integration of productions of different manufacturers can be implemented using OPC. OPC has characters as openness, high efficiency, inter-connection, and industrialization, so it has been broadly applied in industrial automation. Following the developing trend of OPC, Modbus-TCP Ethernet is chosen as the research direction of this thesis, and an OPC DA (Data Access) Server, which is based on Modbus-TCP Ethernet and accords with OPC specification 2.0, is developed as a result.Basing on studies on the Modbus/TCP protocol and OPC DA specification, the principle and developing process of OPC DA server based on Modbus-TCP Ethernet are narrated in detail in this thesis. Then, the practical application of this server is introduced based on a process control project.The innovational features of this thesis are as follows:1. Studying on applying Industrial Ethernet in field device layers of control systems.2. Implementing an OPC DA Server that is based on Modbus-TCP Ethernet and accords with OPC specification 2.0. There is no same kind of commercial production in our country presently.3. By using Modbus/TCP OPC DA Server, it's no need providing the special driver for each given device that support Modbus/TCP protocol.