The Development Of EPA Communication Interface Card For Intelligent Instrument

Ethernet for Plant Automation (EPA) was formulated by Zhejiang University, Zhejiang Supcon Co.Ltd and other institutions. It is the first automation standard accepted and released by the International Organization for Standardization in China. The original innovation with independent intellectual property rights has broken the technological monopoly made by many multinational companies in the past 20 years. It also has achieved a breakthrough about international standards in the field of industrial automation. The EPA standard has entered the stage of international standards publishment and what need to do now is to develop EPA-related instruments and promote the EPA international standard. Based on the successful development of intelligent valve positioner, the details of design and development of the related EPA communication card are present in the paper. The AI and AO function blocks are also developed.So that the field instruments applying the interface card may have good interoperability.The main works in the thesis are as following:(1) Introduce the background of the development of fieldbus, analyze the advantages and disadvantages of fieldbus and point out the new direction of development, then drew EPA necessity. After briefly elaborated the technical characteristic of EPA, the EPA communications interface card are designed and developed for the intelligent valve positioner.(2) According to the design of the EPA communication interface card, the design of the software and hardware are described detail. The realization of the communication protocol model, driver module and protocol stack software are described respectively in software design process, and finally gives the design of software framework. In the hardware design process, the specific design schemes are compared, and based on this, to make an overall design of the interface card and gives detailed design of part of the control circuit.(3) Briefly introduced the EPA function blocks standard. Based on the theory, the EPA function blocks are detailed designed. Mainly includes the choice of the development pattern and the specific software realization. Finally introduced the algorithm and the software realization process of two typical EPA function blocks AI and AO.(4) Detailed introduced the development process of the user program of the intelligent valve positioner, including the selection of the users development model, the specific definitions of serial communication program frame. According to the design needs, at last gives the detailed design method of check code.(5) Describe the principle of consistency and interoperability testing. Design test system combining with test demands. Test results show that the interface card passed the consistency and interoperation testing, and also suggest that intelligent valve positioner equipped with the interface card can be successfully applied to the EPA control network...