PM856K01 ABB

For an automation project(especially a medium-to-large-scale control system),it is very important to choose a network.Some people even put forward the concept of”the network is the controller”.First,the network must be open to facilitate the integration of different devices and the expansion of future system scale;secondly,the form of the network is selected according to the transmission performance requirements of different network levels,which requires a deeper understanding of the network standard protocol,Under the premise of the mechanism;in addition,comprehensively consider specific issues such as system cost,equipment compatibility,and site environment applicability,and determine the network standards used at different levels.The performance of a real-time system can be measured from three aspects:time,reliability and application objects.

对于一个自动化工程(特别是中大规模控制系统)来讲，选择网络是很重要的，甚至有人提出了“网络就是控制器”的概念。首先，网络必须是开放的，以方便不同设备的集成及未来系统规模的扩展；其次，针对不同网络层次的传输性能要求来选择网络的形式，这必须在较深入地了解该网络标准的协议、机制的前提下进行；另外，综合考虑系统成本、设备兼容性、现场环境适用性等具体问题，确定不同层次所使用的网络标准。一个实时系统的性能可从时间、可靠性和应用对象三个方面来衡量。