The Study On Communication Of Distributed PLC Network Gateway

Enterprise network is composed of information network and control network. Fieldbus control has a large number of applications. Because there are so many international fieldbus standard, and they are not compatible. The Industrial Ethernet as a new direction of control system network development, has entered gradually into industrial control system networks. So the situation with Multi-standard fieldbus and industrial Ethernet will be long-term coexistence, which gives the users an important question: how to communicate among the fieldbus with different communication protocols and implement the information exchange between fieldbus networks and information networks. To reduce the cost of upgrading the control network, designing a good compatibility, scalable control network architecture, has important practical significance. In this hybrid network architecture with industrial ethernet and multi-standard fieldbus, protocol conversion technology is the key technology.The paper in-depth studies the communication mechanisms of heterogeneous networks. On this basis, PLBEM (Protocol-Library Based on Embedded Middleware) protocol conversion gateway is proposed. Using hierarchical ideology, and software reuse, we design protocol library scalability and portability. The principle components and particle size control of protocol library are defined. Using shared memory technology we realize the exchange of data. Then, the paper design and develop an easily protable, scalable embedded protocol conversion gateway based on ARM. We successfully implement the communication in the hybrid network.For embedded network control system with high real-time characteristics, congestion control algorithm in traditional information network is studied. However, due to the embedded network control system with many unique constraints that is different from the PC network and complex issues of uncertainty in conversion process, so intelligent control fuzzy strategy is a reasonable choice. Therefore, based on the study of AQM (Active Queue Management) congestion control technology, the paper proposes F-AQM(Fuzzy-based AQM) congestion control algorithm. Simulation and actual project application results show that F-AQM algorithm can improve the quality of gateway service.