plc外文文獻(xiàn)譯文

1、Programmable logic controllerA programmable logic controller (PLC) is a digital computer used for automation of electromechanical processes,such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLC is used in many industries and machines.1. HistoryThe PLC was

2、 invented in response to the needs of the American automotive manufacturing industry. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencersand dedicated closed-loop control

3、lers. In 1968 GM Hydramatic issued a request for proposal for an electronic replacement for hard-wired relay systems.The first PLC, designated the 084 because it was Bedford Associates eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufactur

4、ing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner.One of the very first 084 models that was pres

5、ented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range until the 984 made its appearance.2. DevelopmentEarly PLCs were designed to replace relay logic systems. These PLCs were programmed in lad

6、der logic, which strongly resembles a schematic diagram of relay logic. Other early PLCs used a form of instruction list programming, based on a stack-based logic solver.Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and

7、C. Another method is State Logic, a very high-level programming language designed to program PLCs based on state transition diagrams.3. FunctionalityThe functionality of the PLC have sequential relay control, motion control, process control, distributed control systems and networking.Regarding the p

8、racticality of these desktop computer based logic controllers, it is important to note that they have not been generally accepted in heavy industry becausethe desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to t

9、he same levels of tolerance to temperature,In more recent years, small products called PLRs (programmable logic relays), are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are involved, and low cost is desired. Popular nam

10、es include PICO Controller, NANO PLC, and other names implying very small controllers. the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic.4. PLC compared with other

11、 control systemsPLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changesto the system would be expected du

12、ring its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so t

13、he cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a generic solution, and

14、 where the non-recurring engineering charges are spread over thousands or millions of units.A microcontroller-based design would be appropriate where hundreds or thousandsof units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and

15、certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit

16、 busses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomic.Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integr

17、ated with PLC so that G-code (involving a CNC machine) can be used to instruct machinemovements.PLCs may include logic for single-variable feedback analog control loop, a proportional, integral, derivative or PID controller. A PID loop could be used to control the temperature of a manufacturing proc

18、ess, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has be

19、come less distinct.PLCs have similar functionality as Remote Terminal Units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs and DCSs are increasingly beginning to overlap in responsibilities, and many v

20、endors sell RTUs with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments.5. The prospects f

21、or PLC.The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. PLCs read limit switches, analog process variables (such as temperature and pressure), and the posi

22、tions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules a

23、ttached to a computer network that plugs into the PLC. 5.2System scaleA small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O. Modular PLCs have a chassis (also called a rack) into which are place

24、d modules with different functions. The processor and selection of I/O modules is customised for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special high speed serial I/O link is used so that racks can be distri

25、buted away from the processor, reducing the wiring costs for large plants.5.3User interfacePLCs may need to interact with people for the purpose of configuration, alarm reporting or everyday control. A simple system may use buttons and lights to interact with the user. Text displays are available as

26、 well as graphical touch screens.More complex systems use a programming and monitoring software installed on a computer, with the PLC connected via a communication interface.5.4CommunicationsPLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or Ethernet. Modbus, BA

27、Cnet or DF1 is usually included as one of the communications protocols. Other options include various fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protocols.Most modern PLCs can communicate over a network to some other

28、 system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser.PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the sub

29、systems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations.可編程邏輯控制器可編程邏輯控制器（PLC）或可編程序控制器是用于機(jī)電過程自動化的數(shù)字 計(jì)算機(jī)，例如控制機(jī)械廠生產(chǎn)線、游樂設(shè)施或照明的裝置。可編程控制器可在許 多工業(yè)和機(jī)器中使用。1. 歷史PLC發(fā)明是針對于美國汽車制造行業(yè)的需要?？删幊踢壿嬁刂破髯畛跬ㄟ^了 在軟件版本更換硬連線的控制板生產(chǎn)模

30、式更改時(shí)的汽車工業(yè)。在PLC之前，控制、程序化和安全聯(lián)鎖邏輯制造汽車是使用上百或上千的繼電器、凸輪計(jì)時(shí)器、 鼓定序儀和專用的閉環(huán)控制器來完成的。在 1968年GM Hydramatic發(fā)布通用汽 車公司的提議，電子替代布線中繼系統(tǒng)。第一個(gè)PLC選定084,因?yàn)樗秦惖酶５猛碌牡诎耸膫€(gè)項(xiàng)目。貝得福得同事建立了一家新的公司致力開發(fā)、生產(chǎn)、 銷售，和服務(wù)這一新產(chǎn)品：Modicon，代表模塊化數(shù)字控制器。1977年古爾德電 子公司當(dāng)前所有者收購法國施耐德電氣公司同德國公司AEG并售予該品牌為Modicon。這是專門為通用汽車服務(wù)的，并且經(jīng)過了近二十多年的不間斷服務(wù)。 直至984出現(xiàn)，Modicon

31、使用的84名字才在其產(chǎn)品范圍中結(jié)束。2. 發(fā)展早期的可編程控制器是設(shè)計(jì)來取代繼電器邏輯系統(tǒng)。這些可編程控制器的 “階梯邏輯”是與繼電器邏輯示意圖非常類似的。 其他早期的可編程控制器使用 指令列表編程，基于一個(gè)堆棧編程邏輯求解器進(jìn)行求解?，F(xiàn)代可編程控制器在各種各樣的方式可以被編程，從梯形邏輯語言到更加傳 統(tǒng)的編程語言例如BASIC和C語言。另一個(gè)方法是狀態(tài)邏輯，被設(shè)計(jì)的一種非 常高級編程語言根據(jù)狀態(tài)轉(zhuǎn)換圖的可編程控制器編程。3. 功能PLC的功能包括連續(xù)的繼電器控制，運(yùn)動控制，過程控制，分布式控制系統(tǒng) 和網(wǎng)絡(luò)。在重工業(yè)中PLC被認(rèn)為沒有這些桌面計(jì)算機(jī)為主的邏輯控制器的實(shí)際 性強(qiáng)，因?yàn)镻LC在臺式

32、計(jì)算機(jī)系統(tǒng)中運(yùn)行不是很穩(wěn)定，并且，因?yàn)榕_式計(jì)算機(jī) 硬件沒有被設(shè)計(jì)成耐溫度、濕氣、振動和耐用作為可編程控制器的處理器。在近些年，小產(chǎn)品稱為PLR （可編程邏輯繼電器）已經(jīng)應(yīng)用于輕工業(yè)， 它只 有少部分的輸入/輸出（例如一些真實(shí)的輸入輸出信號）參與，低成本，很理想。 俗名包括PICO控制器、納米PLC和其他的小控制器。PLR通常是模塊化，大 大擴(kuò)展,控制器通常不會取模塊化并且不是可擴(kuò)展的，但是他們提供穩(wěn)健設(shè)計(jì)的 確定性和執(zhí)行邏輯的價(jià)值比PLC少。4. PLC相比其它控制系統(tǒng)可編程控制器是可適應(yīng)一系列自動化任務(wù)。 這些都是自動化的在制造中通常工業(yè)過程開發(fā)和維護(hù)自動化系統(tǒng)的成本在哪里高， 相對于總成本

33、和其壽命期間預(yù) 計(jì)將對系統(tǒng)更改?？删幊炭刂破靼斎牒洼敵鲈O(shè)備兼容工業(yè)試驗(yàn)設(shè)備和管制， 小電氣的設(shè)計(jì)問題對預(yù)期操作是必要的。PLC應(yīng)用程序通常是高度定制系統(tǒng)，因 此成本包裝可編程序控制器（PLC）的費(fèi)用比一個(gè)具體定制設(shè)計(jì)的小控制器要高。 另外一方面在批量生產(chǎn)貨物的情況下自定義的控制系統(tǒng)是組成、成本較低的最佳選擇，而不是一個(gè)非反復(fù)出現(xiàn)工程費(fèi)用“普通”的解決方案。一種基于微控制器的設(shè)計(jì)是需要成百上千個(gè)單位（設(shè)計(jì)電源供應(yīng)器，輸入/輸出硬件和必要的檢測和認(rèn)證）和開發(fā)成本可以分散到很多的銷售，最終用戶不 需要更改該控件。汽車應(yīng)用程序就是一個(gè)例子：數(shù)以百萬計(jì)的內(nèi)置單位每一年需 要建造，很少最終用戶更改這些控制器的編程。 然而，一些其他車輛如交通公共 汽車經(jīng)常定制設(shè)計(jì)的控制，而不是用PLC，因?yàn)閿?shù)量很低，發(fā)展成本會賺不到錢的。可編程序控制器廣泛用于運(yùn)動控制、 定位控制和轉(zhuǎn)矩控制。一些制造商生產(chǎn) 運(yùn)動控制單元與PLC集成、G-code （涉及數(shù)控機(jī)床）可以用于指導(dǎo)機(jī)器運(yùn)作。可編程控制器可能包括一個(gè)“比例，積分，微分”的單變量反饋模擬控制循 環(huán)的邏輯或“控制器”。以PID回路可用于