工业网络通信

　　工业网络通信

　　工业应用中的联网问题有着悠久而相当混乱的历史。每一个行业都面临着在单个设备上部署电子控制的任务，将这些控制连接到自动化的孤岛上，最后将这些岛屿拉进一个工厂范围内的网络。它们现在与企业网络相连，并与销售预测、库存控制和管理信息系统等相关联。然而，这超出了这一块的范围。这种方法的问题是，不同的行业开发了不同的实现网络的方法。在20世纪80年代，有一种运动，用ISO来创建一个描述OSI（开放系统互连）模型的网络的通用方法，并使用这种模型来发现不同网络技术的交互方式。本文将通信视为七层模型。第1级是物理层，它定义了电线、连接器和信号穿越导线（或光纤）的方式。这些层变得越来越抽象，直到第7层，应用层，它是网络和通信软件之间的接口。

　　At the time there was a huge investment in OSI activities， with an important legacy consisting of the ability to describe current networking technologies in terms of the relevant OSI layers， even if they were not designed with that approach.

　　Today there are several networking technologies being deployed. Industrial Ethernet is making steady progress， particularly as it is seen as compatible with standard Ethernet. While it has significant plus points， it does have some disadvantages， particularly for hard real-time applications. Despite this， many earlier networking technologies， such as Modbus and Profibus， have been adapted as overlays on Ethernet.