3、现场总线控制系统体系结构
如图1所示，最底层的Infranet控制网即FCS，各控制器节点下放分散到现场，构成一种彻底的分布式控制体系结构，网络拓扑结构任意，可为总线形、星形、环形等，通讯介质不受限制，可用双绞线、电力线、无线、红外线等各种形式。FCS形成的Infranet控制网很容易与Intranet企业内部网和Internet全球信息网互连，构成一个完整的企业网络三级体系结构。
4、现场总线控制系统的特点
（1）开放性和可互操作性
开放性意味FCS将打破DCS大型厂家的垄断，给中小企业发展带来了平等竞争的机遇。可互操作性实现控制产品的“即插即用”功能，从而使用户对不同厂家工控产品有更多的选择余地。
（2）彻底的分散性
layout, due to the use of TCP/IP protocol, the system can also use the public telephone network (dial-up mode) or satellite to achieve ultra-long-distance communication.
Subsystems such as PLC communicate with the Industrial” system through the ModBus protocol interface. The system also supports IEC870-5 over-control protocol.
discussion.
The Flash EPROM inside the PS provides more than 220 functional modules (control algorithm subroutines), in addition to the basic ones specified in the IEC 61131 3 standard
In addition to this content, many powerful and rigorously tested function blocks from actual engineering applications have been expanded. any complex control
The scheme can be realized by the combination of these function blocks.
The function blocks provided by the system mainly include the following categories:
o
Analog processing
o
digital processing
loop regulation
Logical sequence control
c
logic operation
Monitoring function
Collection function.
c
arithmetic operations
c
