【正文】 d find in a DCS. A PLC would have preprogrammed I/O cards for specific signal types and ranges. In th。ve moved past their birthplace: the digital world (switch and binary sensor inputs and output contacts to run motors and trigger solenoids). PLCs are fast: They run an inputputeoutput cycle in milliseconds. On the other hand, DCSs offer fractional second (1/2 to 1/10) control cycles. However, some DCSs provide interrupt/eventtriggered logic for highspeed applications. PLCs are simple, rugged puters with minimal peripherals and simple OSs. While increasing reliability, PLC simplicity is not conducive to redundancy. Thus, fully redundant (hot, automatic, bumpless) variations of PLCs, with their added hardware and software, sometimes suffer from a reduction in their reliabilitya characteristic PLCs are famous for. Data exchange typically requires you to preassign data registers and hard code their addresses into the logic. If you add registers or need to reassign data, you typically have to deal manually with the Domino Effect. Typical PLC Relay Ladder Logic (RLL) languages include function blocks that can perform plex control and math functions (., PID algorithms). Complex multiloop control functions (., cascade management and loop initialization) are not typical. For functions too messy to implement in RLL, most PLCs provide a function block that calls a userwritten program (usually in BASIC or C). PLCs typically operate as state machines: They read all inputs, execute through the logic, and then drive the outputs. The userwritten logic is typically one big RLL program, which means you may have to take the whole PLC offline to make a change of any size. You also run into database synchronization problems because of the separation of PLCs and the Man Machine Interface (MMI) software packages, as opposed to the central databases of DCSs. A PLC will run in a standalone configuration. A DCS controller normally expects an operator interface and munications, so it can send alarms, messages, trend updates, and display updates. Many PLC installations use interface software from thirdparty vendors for improved graphics and various levels of alarming, trending, and reporting. The PLC and MMI software normally interact by sitting on the network and using the register exchange mechanism to get data from and to the various PLCs. This type of munication presumes you have preassigned data registers and can fetch data on an absolute address basis. This can lead to data processing errors (., from the wrong input) you won39。 thus, making changes to part of the control logic has no impact on the rest. An important difference between DCSs and PLCs is how vendors market them. DCS vendors typically sell a plete, working, integrated, and tested system。s DCS may control through networked smart deviceswith no I/O hardware of its own.Most DCSs offer redundant controllers, networks, and I/Os. Most give you builtin redundancy and diagnostic features, with no need for userwritten logic. DCSs allow centralized configuration from the operator or engineering console in the control room. You can change programming offline, and download without restarting the system for the change to be effective.DCSs allow intercontroller munications. You can do data exchange in most DCS systems ad hoc (no need for predefined data point lists). You access data by tag name, regardless of hardware or location. DCSs use multitasking operating systems, so you can download and run applications aside from the realtime control functions and still do fractionalsecond control. DCSs now e in micro systems, to pricepete with PLCsbut with full DCS features and capabilities. The typical DCS has integrated diagnostics and standard display templates that automatically extend/update when your database changes. This database is central to the systemyou don39。參考文獻：[1] 陳嬋娟, 祁廣利 《PLC電氣控制技術(shù)》 [M] 化學工業(yè)出版社 [2] 馬丁 《西門子PLC常用模塊與工業(yè)系統(tǒng)設(shè)計實例精講》 [M] 電子工業(yè)出版社 [3] 廖常初 《S7200 PLC基礎(chǔ)教程》 [M] 機械工業(yè)出版社 [4] 何波 《電氣控制及PLC控制》 [M] 中國電力出版社 [5] 薛曉明《變頻器技術(shù)與應(yīng)用》 [M] 北京理工大學出版社 [6] 姚錫祿 《變頻器控制技術(shù)入門與應(yīng)用實例》 [M] 中國電力出版社. [7] 孟曉芳 《 西門子系列變頻器及其工程應(yīng)用》[M] 機械工業(yè)出版社. [8] 李偉龍 張文學 《變頻器技術(shù)介紹》 [J] 船電技術(shù) [9] 康梅, 朱莉, 陳山編 《變頻器使用指南》[M] 化學工業(yè)出版社 [10] 張燕賓 《變頻器應(yīng)用教程》 [M] 機械工業(yè)出版社 [11] 德國西門子公司《SIEMENS MICROMASTER 420通用型變頻器使用大全》[Z] [12] 鄧其貴 《變頻器操作與工程項目應(yīng)用》[M] 北京理工大學出版社 [13] 馮垛生 《變頻器實用指南》 [M] 人民郵電出版社 [14] 宋伯生 《PLC編程實用指南》 [M] 機械工業(yè)出版社 [15] 張均 《小型音樂噴泉控制系統(tǒng)設(shè)計》 [J] 江西農(nóng)業(yè)大學學報，1999，21 [16] 李瑞程，應(yīng)柏青 《音樂噴泉控制系統(tǒng)的設(shè)計及PLC實現(xiàn)》[J] 實驗技術(shù)與管理， 2008，25（5）[17] 林 濤，楊慶斌，寧福軍，姜宜寬《PLC在音樂噴泉控制系統(tǒng)中的應(yīng)用》 [J]青島大學學報(工程技術(shù)版)，2008，23（4）[18] 王世橋，王玲，路晉泰《變頻器、CP控制器在音樂噴泉中的應(yīng)用》 [J] 機械工程師，2007，（9）[19] 德國西門子公司《 SIEMENS SIMATIC S7200可編程序控制器系統(tǒng)手冊》[Z] 1999[20] 陳顯寧，高宏才 《變頻調(diào)速器及PLC在音樂噴泉中的應(yīng)用》[J] 昆明理工大學學報，1999，24（5）附錄1 音樂噴泉控制程序附錄2 英文原文PLC or DCS: What is the difference?Turn the clock back 1015 years: The programmable logic controller (PLC) is king of machine control while the distributed control system (DCS) dominates process control. If you manufacture plastic widgets, you speak PLC. If you produce chemicals, you speak DCS. Today, the two technologies share kingdoms as the functional lines between them continue to blur. We now use each where the other used to rule. However, PLCs still dominate highspeed machine control, and DCSs prevail in plex continuous processes. The early DCS looked dramatically different from the early PLC. Initially, the DCS performed the control functions of the analog panel instruments it replaced, and its interface mimicked their panel displays. DCSs then gained sequence logic capabilities to control batch processes as well as continuous ones. DCSs performed hundreds of analog measurements and controlled dozens of analog outputs, using multivaria