ABB主板 控制板 通讯板 电源板 RMIO-11C

ABB主板 控制板 通讯板 电源板 RMIO-11C

现场总线的本质是信息处理现场化

一个控制系统，无论是采用DCS还是采用现场总线，系统需要处理的信息量至少是一样多的。实际上，采用现场总线和智能仪表后，可以从现场得到更多的诊断、维护和管理信息。现场总线系统的信息量大大增加了，而传输信息的线缆却大大减少了。这就要求一方面要大大提高线缆传输信息的能力、减少多余信息的传递。另一方面要让大量信息在现场就地完成处理，减少现场与控制机房之间的信息往返。如果仅仅把现场总线理解为省掉了几根电缆，是没有理解到它的实质。信息处理的现场化才是智能化仪表和现场总线所追求的目标，也是现场总线不同与其它计算机通信技术的标志。

网络的设计

一般控制系统也有网络设计问题，网络设计的是从物理形态上考虑通信网络和输入、输出线缆网络的布置。前面提到许多现场总线的网络形态是线形的，每一组网段上的节点数是有限制的。由于网段上的节点数较少，因此除考虑网络的物理布置之外，还要考虑减少信息在网络上的往返传递。减少信息的往返传递是现场总线系统中网络设计和系统组态的一条重要原则。减少信息往返常常可带来改善系统响应时间的好处。因此，网络设计时应将相互间信息交换量大的节点，放在同一条支路里。例如多回路调节中，一个调节回路的节点应尽量放置在同一条支路里。

The essence of fieldbus is the information processing field

A control system, whether using DCS or fieldbus, needs to process at least the same amount of information. In fact, after the use of fieldbus and intelligent meters, you can get more diagnosis, maintenance and management information from the field. The amount of information in the fieldbus system is greatly increased, while the cables to transmit the information are greatly reduced. This requires on the one hand to greatly improve the ability of cable transmission information, reduce the transmission of excess information. On the other hand, a large amount of information should be processed on-site to reduce the information roundtrip between the site and the control room. If only the fieldbus is understood as the elimination of a few cables, it is not understood its essence. The field of information processing is the goal of intelligent instrument and fieldbus, and also the symbol of fieldbus which is different from other computer communication technology.

Network design

The general control system also has the problem of network design, which is to consider the layout of the communication network and the input and output cable network from the physical form. As mentioned earlier, the network form of many fieldbuses is linear, and the number of nodes on each networking segment is limited. Due to the small number of nodes on the network segment, in addition to considering the physical layout of the network, it is also necessary to consider reducing the round-trip transmission of information on the network. Reducing the round-trip transmission of information is an important principle of network design and system configuration in fieldbus systems. Reducing information roundtrips often has the benefit of improving system response time. Therefore, when designing the network, nodes with large information exchange capacity should be placed in the same branch. For example, in multi-loop regulation, the nodes of one regulation loop should be placed in the same branch as far as possible.