什么是分布式控制系统|过程自动化

A distributed control system (DCS) is a computerised control system for a process or plant usually with a large number of control loops, in which autonomous controllers are distributed throughout the system, but there is central operator supervisory control. This is in contrast to systems that use centralized controllers; either discrete controllers located at a central control room or within a central computer. The DCS concept increases reliability and reduces installation costs by localising control functions near the process plant, with remote monitoring and supervision.

Distributed control systems first emerged in large, high value, safety critical process industries, and were attractive because the DCS manufacturer would supply both the local control level and central supervisory equipment as an integrated package, thus reducing design integration risk. Today the functionality of SCADA and DCS systems are very similar, but DCS tends to be used on large continuous process plants where high reliability and security is important, and the control room is not geographically remote.

What is the difference between PLC and DCS?

PLC代表Programmable Logic Controller可以处理存储在其存储器中的逻辑语句的二进制输入和输出。它是通过编程系统存储在其存储器中的数字操作系统。

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Programmable Logic Controllers, are frequently used to synchronize the flow of inputs from sensors (Physical) and events with the flow of outputs to actuators and events. This leads to precisely controlled actions that permit a tight control of almost any industrial process.
这实际上是一个由可编程微处理器组成的控制设备，并使用专用计算机语言编程。
之前，可编程逻辑控制器将以梯形逻辑编程，其类似于继电器逻辑的示意图。
现代可编程逻辑控制器通常以几种语言中的任何一种编程，从梯形图逻辑到基本或C.
Typically, the program is written in a development environment on a personal computer (PC), and then is downloaded onto the programmable logic controller directly through a cable connection.
The program is stored in the programmable logic controller in non-volatile memory.Programmable logic controllers contain a variable number of Input/Output (I/O) ports, and are typically Reduced Instruction Set Computer (RISC) based.
它们专为实时使用而设计，并且通常必须在车间上承受恶劣的环境。
2. DCS stands for Distributed Control systems
分布式控制系统通过此次控制所有类型的过程变量，我们可以控制整个工厂，我们可以看到植物的状态和处理单元。
它是将工厂或过程控制分为几个责任领域的系统，每个责任都是由自己的控制器管理的，整个系统都连接到形成单个实体，通常通过通信总线。
(DCS) refers to a control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers. The entire system of controllers is connected by networks for communication and monitoring.
A DCS typically uses custom designed processors as controllers and uses both proprietary interconnections and Communications protocol for communication.
Input & output modules form component parts of the DCS. The processor receives information from input modules and sends information to output modules.
输入模块从进程（A.k.a.字段）中的输入仪器接收信息，并将指令发送到现场的输出仪器。
Computer buses or electrical buses connect the processor and modules through multiplexer or de-multiplexers.
Buses also connect the distributed controllers with the central controller and finally to the Human-Machine Interface (HMI) or control consoles.