外文翻譯---控制裝置和可編程邏輯控制

1、<p><b>　　中文3475字</b></p><p>　　Control Devices and PLC</p><p>　　Joseph La Fauci</p><p>　　From Wikipedia, the free encyclopedia</p><p>　　Several types of

2、 control devices are used in industry to satisfy the following control needs.</p><p>　　Mechanical Control、Pneumatic Control、Electromechanical Control、Electronic Control、Computer Control、Programmable Logic Co

3、ntrol (PLC)</p><p>　　Mechanical control includes cams and governors. Although they have been used for the control of very complex machines, to be cost effectively, today they are used for simple and fixed-cy

4、cle task control. Some automated machines, such as screw machines, still use cam-based control. Mechanical control is difficult to manufacture and is subject to wear.</p><p>　　Pneumatic control is still very

5、 popular for certain applications. It uses compressed air, valves, and switches to construct simple control logic, but is relatively slow. Because standard components are used to construct the logic, it is easier to buil

6、d than a mechanical control. Pneumatic control parts are subject to wear.</p><p>　　As does a mechanical control, an electromechanical control use switches, relays, timers, counters, and so on, to construct l

7、ogic. Because electric current is used, it is faster and more flexible. The controllers using electromechanical control are called relay devices.</p><p>　　Electric control is similar to electromechanical con

8、trol, except that the moving mechanical components in an electromechanical control device are replaced by electronic switches, which works faster and is more reliable.</p><p>　　Computer control is the most v

9、ersatile control system. The logic of the control is programmed into the computer memory using software. It not only can be for machine and manufacturing system control, but also for data communication. Very complex cont

10、rol strategies with extensive computations can be programmed. The first is the interface with the outside world. Internally, the computer uses a low voltage (5 to 12 volts) and a low current (several milliamps). Machine

11、requires much higher voltages </p><p>　　In order to use the advantages of all those controllers and eliminate the difficulties, the programmable logic controllers were invented. A PLC was a replacement for r

12、elay devices. They are programmed using a ladder diagram, which is standard electric wiring diagram. As PLCs become more flexibility, high-level as well as low-level languages are available to PLC programmers. PLCs have

13、the flexibility of computers as well as a standard and easy interface with processes and other devices. They are </p><p>　　Automatic of many different processes, such as controlling machines or factory assem

14、bly lines, is done through the use of small the computers called a programmable logic controller (PLC), PLCs were first created to serve the automobile industry, and the first PLC project was developed in 1968 for Genera

15、l Motors to replace hard-wired relay systems with an electronic controller. Since the advent of PLCs, the ability to centralize factory processes, especially in the automotive industry, has improv</p><p>　　A

16、utomatic control has become an important consideration in most industrial processes where certain repetitive operations are performed. This applies to situations such as the automatic assembly of modules and products whe

17、re a cycle of events is conducted in a consistent and uniform manner. Applications generally include a combination of feeding, handing, drilling, cutting, assembling, discharging, inspecting, packaging and transporting b

18、y conveyor.</p><p>　　Prior to the introduction of computer-based control systems the automation of such events was achieved by using either electrical relay logic circuits or pneumatic logic circuits. Althou

19、gh these are conceptionally simple and easy to maintain, they are somewhat bulky and can be expensive. More important is the fact that the resulting control circuits are inflexible and do not lend themselves to easy syst

20、em control alterations. </p><p>　　The late 1960s saw the introduction of the programmable logic controller (PLC) as a direct replacement for the relay sequence controllers. In essence the PLC replaces the

21、hardwired relay or pneumatic logic with a more flexible programmable logic. It offers a simple, flexible and low-cost means of implementing a sequence control strategy where outputs for switching devices on and off are s

22、et according to input conditions as read from digital sensor states. It should be noted that, particularly in</p><p>　　The PLC is composed of the same ingredients as a microcomputer such as a microprocessor,

23、 memory and input/output facilities. The processor executes the instructions held in memory by operating on inputs derived from the controlled process and providing outputs in accordance with the logic sequence defined i

24、n the control program. Its basic principle of operation during the execution of the program is that the program is scanned very fast, typically 1 to 20 us per step, to record all input states.</p><p>　　Small

25、 PLCs dedicated to sequential control have typically 12 inputs and 8 outputs with the possibility of expansion up to 128 I/O lines. They come complete with an input interface to accommodate a range of input signals from

26、the controlled process which are then converted to an appropriate from for the processor. Similarly, provision is made at the output of the PLC to interface with a variety of process hardware such as lamps, motors, relay

27、s and solenoids. The typical handing voltages are 24V D</p><p>　　Program instructions can be input into the battery backup RAM of a PLC by means of either a hand-held programming keypad or a connected PC wit

28、h an appropriate software development package. Some LCD programming consoles incorporate a limited graphical display which illustrates the program in ladder logic format as the programmer builds it up using symbolic keys

29、. This is also the principle of the PC-based development system where additionally the programmer has access to a lager visual display and</p><p>　　There are a large number of manufacturers of PLCs. Although

30、 some use their own particular software language the majority are based on the ladder logic diagram. Historically this was introduced in order to gain the acceptance of customers who were interested in moving from hardwi

31、red relay control systems to the PLC. In addition to the basic input/output facilities the PLC also contains timers, counters and other special functions.</p><p>　　As PLC technology has advanced, so have pro

32、gramming languages and communications capabilities, along with many other important features. Today’s PLCs offer faster scan times, space efficient high-density input/output systems, and special interfaces to allow non-t

33、raditional devices to be attached directly to the PLC. Not only can they communicate with other control systems, they can also perform reporting functions and diagnose their own failures, as well as the failure of a mach

34、ine or process.</p><p>　　Size is typically used to categorize today’s PLC, and is often an indication of the features and types of applications it will accommodate. Small, non-modular PLCs (also known as fix

35、ed I/O PLCs) generally have less memory and accommodate a small number of inputs and outputs in fixed configurations. Modular PLCs have bases or racks that allow installation of multiple I/O modules, and will accommodate

36、 more complex application.</p><p>　　When you consider all of the advances PLCs have made and all the benefits they offer, it’s easy to see how they’ve become a standard in the industry, and why they will mos

37、t likely continue their success in the future.</p><p>　　Communicating with a variety of other control devices has not been strength of traditional PLC networks. Many industrial controllers are quipped with a

38、n RS232 serial port for the transfer of data to and from other digital control devices in a system.</p><p>　　PLCs face ever more complex challenges these days. Where once they quietly replaced relays and gav

39、e an occasional report to a corporate mainframe, they are now grouped into cells, given new jobs and new languages, and are force to compete against a growing array of control products. For this year’s annual PLC technol

40、ogy update, we queried PLC makers on these topics and more.</p><p>　　Higher level PLC programming languages have been around for some time, but lately their popularity has been mushrooming. As Raymond Leveil

41、le, vice president & general manager, Siemens Energy & Automation, Inc. Programmable Controls Division, points out: “ As programmable controls are being used for more and more sophisticated operations, languages

42、other than ladder logic become more practical, efficient, and powerful. For example, it’s very difficult to write a trigonometric function using ladde</p><p>　　Thus far, PLCs have not been used extensively f

43、or continuous process control. Will this continue? “The feeling that I’ve gotten,” says Ken Jannotta, manager, product planning, Series one and Series Six product, at GE Fanuc North America, “is that PLCs will be used in

44、 the process industry but not necessarily for process control.”</p><p>　　Several vendors-obviously betting that the opposite will happen-have introduced PLCs optimized for process applications. Rich Ryan, ma

45、nager, commercial marketing, Allen-bradley Programmable Controls Div. cites PLCs’ increasing use in such industries as food, chemicals, and petroleum.</p><p>　　While there are concerns about the lack of comp

46、atible communications between PLCs from different vendors, the connection at the other end-the I/O-is even more fragmented. With rare exceptions, I/O is still proprietary. Yet there are those who feel that I/O will event

47、ually become more universal. GE Fanuc is hoping to do that with its Genius smart I/O line. The independent I/O makers are pulling in the same direction.</p><p>　　Many say that I/O is such a high-value item t

48、hat PLC makers will always want to keep it proprietary. As Ken Jannotta, says: “The I/O is going to be a disproportionate amount of the hardware sale. Certainly each PLC vendor is going to try to protect that.” For that

49、reason, he says, PLC makers won’t begin selling universal I/O systems from other vendors. “If we start selling that kind of product,” says Jannotta, “what do we manufacture?”</p><p>　　With more intelligent I

50、/O appearing, Sal Provanzano feels this will lead to more differentiation among I/O from different makers. “Where the I/O becomes extremely intelligent and becomes part of the system,” he says, “it really is hard to defi

51、ne which is the I/O and which is the CPU. It really starts to become distributed processing. Now, in order for that distributed processing to work, the CPU, if you will, is equally integrated into the system as the I/O.”

52、</p><p>　　While different PLCs probably will continue to use proprietary I/O, several vendors make it possible to connect their I/O to IBM PC (personal computer)-compatible equipment. Allen-bradley, Gould, a

53、nd Cincinnati Milacron already have, and rumor has it that GE is planning something along these same lines. </p><p>　　“There are inherent architectural differences between a general purpose computer,” says R

54、ich Ryan, “and a programmable controller. There are hardware constructs built into almost every manufacturer’s programmable controller today that customize the hardware to run ladder logic and to solve machine code.” One

55、 fundamental difference he cites is called state of the machine. Ryan: “When you shut the machine off, or interrupt the cycle, or you jump to another spot in the cycle, programmable controlle</p><p>　　控制裝置和可

56、編程邏輯控制</p><p><b>　　約瑟夫.拉福奇</b></p><p><b>　　維基自由百科全書(shū)</b></p><p>　　工業(yè)用的幾種控制裝置是為了滿足以下一些控制要求：</p><p>　　機(jī)械控制、氣動(dòng)控制、機(jī)電控制、電子控制、計(jì)算機(jī)控制、可編程控制。</p>&

57、lt;p>　　機(jī)械控制包含有凸輪和調(diào)速器。盡管它們?cè)糜趯?duì)非常復(fù)雜機(jī)器的控制，也比較經(jīng)濟(jì)，但現(xiàn)在它們僅僅用于簡(jiǎn)單的固定循環(huán)控制中。一些自動(dòng)機(jī)床，如攻螺紋機(jī)床，仍舊使用基于凸輪的控制。機(jī)械控制的缺點(diǎn)是裝置制造困難。</p><p>　　氣動(dòng)控制對(duì)于某些應(yīng)用仍很流行。它利用壓縮空氣、閥門(mén)及開(kāi)關(guān)構(gòu)成簡(jiǎn)單的控制邏輯，但它的速度相對(duì)較慢。由于采用標(biāo)準(zhǔn)件構(gòu)成控制邏輯，因此它比一個(gè)機(jī)械控制裝置更易于加工制造。氣動(dòng)控制元件

58、同樣易于磨損。</p><p>　　正像機(jī)械控制那樣，機(jī)電控制也使用開(kāi)關(guān)、繼電器、定時(shí)器、計(jì)數(shù)器等構(gòu)成控制邏輯，因?yàn)椴捎昧穗娏鱽?lái)控制，所以它更快，更靈活。使用機(jī)電控制的控制器稱(chēng)為繼電器控制。</p><p>　　除了將機(jī)電控制裝置中的機(jī)電控制元件用觸點(diǎn)開(kāi)關(guān)代替外，電子控制類(lèi)似于機(jī)電控制，控制速度更快且更可靠。</p><p>　　計(jì)算機(jī)控制是最通用的控制系統(tǒng)。其控制

59、邏輯是實(shí)用軟件將其程序化后存入計(jì)算機(jī)內(nèi)存中。它不僅用于機(jī)床及制造系統(tǒng)控制，而且也可以用于數(shù)據(jù)通訊。具有龐大計(jì)算量的非常復(fù)雜的控制策略也能被程序化。首先要解決與外界的連接，在控制電路內(nèi)部計(jì)算機(jī)使用低電壓（5～12V）和小電流（幾毫安），機(jī)床的外部主電路則需要高電壓（24，110或220V）和大電流（以A計(jì)算），接口不僅要進(jìn)行不同電壓的轉(zhuǎn)換，而且必須對(duì)車(chē)間中通常存在的電噪聲加以過(guò)濾，這種接口對(duì)不同應(yīng)用來(lái)說(shuō)也必須是用戶(hù)定做的。</p&g

60、t;<p>　　為了利用那些控制器的優(yōu)勢(shì)，消除弊端，可編程邏輯控制器（PLC）應(yīng)運(yùn)而生，一個(gè)PLC就能代替整個(gè)繼電器控制裝置，他們用梯形圖（梯形圖是標(biāo)準(zhǔn)的電路圖）編程。由于PLC的編程靈活性逐漸增強(qiáng)，既可使用高級(jí)語(yǔ)言也可使用低級(jí)語(yǔ)言。PLC不僅用于計(jì)算機(jī)的靈活性，同時(shí)也具有與處理過(guò)程及其它裝置聯(lián)接的界面標(biāo)準(zhǔn)簡(jiǎn)易的特點(diǎn)。在工業(yè)上，從單一設(shè)備到復(fù)雜的制造設(shè)備都廣泛使用PLC控制。</p><p>　　自

61、動(dòng)化應(yīng)用于許多不同的過(guò)程，如控制機(jī)器或工廠裝配線的工作是通過(guò)使用被稱(chēng)為可編程邏輯控制器（ PLC ）的小型計(jì)算機(jī)實(shí)現(xiàn)的。PLC的首次創(chuàng)造是為了服務(wù)汽車(chē)產(chǎn)業(yè)，PLC在1968年被開(kāi)發(fā)為美國(guó)的通用公司以一個(gè)電子控制器。取代硬連線中繼系統(tǒng)。自從PLC出現(xiàn)以來(lái)，工廠的有了生產(chǎn)過(guò)程的集中能力，尤其是在汽車(chē)行業(yè)有較大提高。</p><p>　　對(duì)于大多數(shù)工業(yè)生產(chǎn)中的某些重復(fù)操作來(lái)說(shuō)，自動(dòng)化控制已經(jīng)成為一個(gè)重要的考慮因素。自動(dòng)

62、化控制也適用于諸如自動(dòng)化裝配模塊和一系列按固定模式生產(chǎn)的產(chǎn)品，其應(yīng)用過(guò)程一般由以下幾項(xiàng)組成即：進(jìn)料、操作、鉆、切割、裝配、卸貨、檢驗(yàn)、包裝及用傳送帶傳送。</p><p>　　在以計(jì)算機(jī)為基礎(chǔ)的控制系統(tǒng)之前，自動(dòng)化控制主要通過(guò)使用電子繼電器邏輯電路或啟動(dòng)邏輯電路來(lái)實(shí)現(xiàn)。盡管它們?cè)O(shè)計(jì)簡(jiǎn)單并易于維修，但它們中的一些笨重且價(jià)格昂貴，一個(gè)更重要的事實(shí)是這種控制電路缺乏靈活性，并且不易實(shí)現(xiàn)控制系統(tǒng)的改造。</p>

63、;<p>　　20世紀(jì)60年代末期，可編程控制器（PLC）出現(xiàn)并直接取代了繼電器控制器。在本質(zhì)上PLC以更靈活的可編程邏輯取代了硬繼電器和氣動(dòng)邏輯電路，它提供了一種簡(jiǎn)單靈活且成本低的方案，來(lái)實(shí)施一系列的控制策略。輸出端開(kāi)關(guān)的開(kāi)與關(guān)取決于輸入端從數(shù)字傳感器讀入的信號(hào)。應(yīng)該指出的是在美國(guó)PLC常被稱(chēng)為‘可編程控制器’并縮寫(xiě)為PC，不應(yīng)該把它和個(gè)人電腦‘PC’或IBM個(gè)人電腦混淆。</p><p>　　P

64、LC的組成部分和微機(jī)相同，都有微處理器、存儲(chǔ)器和輸入/輸出設(shè)備。微處理器執(zhí)行的指令來(lái)自于存儲(chǔ)器輸入端所需的控制過(guò)程，并在輸出端輸出按邏輯順序控制的程序。操作的基本原則是：在執(zhí)行該程序時(shí)程序掃描的速度很快，通常是1到20微秒每步以記錄所有的輸入狀態(tài)，輸出端和邏輯程序相對(duì)應(yīng)，該過(guò)程在控制器的整個(gè)掃描周期內(nèi)不斷重復(fù)。</p><p>　　小型PLC的順序控制器通常有12個(gè)輸入端和8個(gè)輸出端，但有可能會(huì)擴(kuò)展到128根輸入

65、/輸出線，它們?nèi)縼?lái)自同一個(gè)輸入接口以容納來(lái)自控制過(guò)程的各種輸入信號(hào)。同樣，在PLC的輸出端接各種硬件設(shè)備，如：燈具、電機(jī)、繼電器和電磁鐵。典型PLC的操作電壓為24V直流電和110V的交流電。</p><p>　　程序指令可以被輸入到PLC的隨機(jī)存儲(chǔ)器中，可以通過(guò)手提式編程鍵盤(pán)輸入，也可通過(guò)與個(gè)人電腦相連的軟件開(kāi)發(fā)包輸入。有些液晶編程控制器能吧特定的圖形顯示出來(lái)，其中顯示了為編程人員在畫(huà)梯形圖中需使用的符號(hào)鍵，

66、這也是基于個(gè)人電腦發(fā)展系統(tǒng)的一個(gè)原則，即編程員進(jìn)入一個(gè)大的可視顯示及PC操作系統(tǒng)對(duì)數(shù)據(jù)進(jìn)行存儲(chǔ)和檢索。一旦程序進(jìn)行了調(diào)試和驗(yàn)證模擬，代碼可以被載入一個(gè)可刪除的只讀存儲(chǔ)器并安裝在PLC中。</p><p>　　目前有大量的PLC制造商，盡管有些人使用他們自己的特殊軟件，但他們中的大部分還是基于梯形圖編程的。歷史上的這次進(jìn)步是為了滿足用戶(hù)從硬繼電器控制到PLC控制的需求，除了基本的輸入/輸出設(shè)備，PLC還包括：定時(shí)器

67、、計(jì)數(shù)器和一些其它特殊功能。</p><p>　　隨著PLC技術(shù)的發(fā)展，有了獨(dú)自的編程語(yǔ)言和很強(qiáng)的通訊能力以及其它一些重要功能。今天的PLC擁有了更快的掃描時(shí)間，更有效的利用空間，高密度的輸入/輸出系統(tǒng)，以及特殊界面，讓非傳統(tǒng)的設(shè)備直接和可編程控制器連接起來(lái)。這不僅可以使其與其他控制系統(tǒng)便捷的交換信息，它們還可以執(zhí)行自診斷功能并發(fā)送報(bào)告，同時(shí)還可以診斷一臺(tái)機(jī)器及過(guò)程的錯(cuò)誤。</p><p>

68、;　　尺寸通常是用來(lái)劃分當(dāng)今的可編程控制器的依據(jù)，并通常用來(lái)顯示特征和各種類(lèi)型可以容納的應(yīng)用程序。小型的非模塊化的PLC（也稱(chēng)為固定輸入/輸出的PLC ），一般有少量的存儲(chǔ)器并且只有少量的輸入/輸出端口。模塊化的PLC有基本端口及可擴(kuò)展端口，允許安裝多個(gè)輸入/輸出模塊，將能容納更復(fù)雜的應(yīng)用程序。</p><p>　　當(dāng)您考慮了所有PLC的發(fā)展以及你所獲得的利益，你很容易知道它們?nèi)绾纬蔀橐粋€(gè)行業(yè)標(biāo)準(zhǔn)，以及為什么他們

69、將最有可能繼續(xù)他們的成功在未來(lái)的一個(gè)時(shí)期內(nèi)。</p><p>　　傳統(tǒng)的PLC網(wǎng)絡(luò)沒(méi)有和其它大量控制設(shè)備溝通的能力，一些工業(yè)控制器配備了一個(gè)RS232的串行接口，可以把數(shù)字傳輸及其它的數(shù)字控制設(shè)備集中在一個(gè)系統(tǒng)中。</p><p>　　當(dāng)今PLC面臨著越來(lái)越復(fù)雜的挑戰(zhàn)，而一旦他們悄悄地取代了繼電器，并而向公司主機(jī)發(fā)送報(bào)告，它們現(xiàn)在越來(lái)越細(xì)化，有了新的任務(wù)及編程語(yǔ)言，并有能力去完成日益增多的

70、控制產(chǎn)品。對(duì)于今年度的PLC技術(shù)更新，我們就這些問(wèn)題詢(xún)問(wèn)了可編程控制器的決策者。</p><p>　　更高水平的PLC編程語(yǔ)言已出現(xiàn)了一段時(shí)間，但是最近它們更是雨后春筍般地蓬勃發(fā)展。作為雷蒙德列維爾，副總裁兼總經(jīng)理，西門(mén)子能源與自動(dòng)化公司的可編程控制司，指出：“可編程控制正被用來(lái)完成更多更復(fù)雜的作業(yè)，語(yǔ)言除了梯形圖外變得更加實(shí)用，高效和強(qiáng)大。舉例來(lái)說(shuō)，采用梯形邏輯圖來(lái)寫(xiě)一個(gè)三角函數(shù)是非常困難的”。 包括布爾編程語(yǔ)

71、言在內(nèi)的語(yǔ)言為越來(lái)越多的人所接受，它們是根據(jù)流程圖編制的，這也使人們對(duì)類(lèi)似C語(yǔ)言和BASIC語(yǔ)言有了更大的興趣。</p><p>　　到目前為止，PLC在過(guò)程的連續(xù)控制中沒(méi)有得到廣泛應(yīng)用，這種現(xiàn)狀是否會(huì)繼續(xù)下去？“我的觀點(diǎn)是”肯捷那特 ，經(jīng)理，產(chǎn)品策劃，是北美的GE公司一個(gè)系列六類(lèi)產(chǎn)品的代表，“PLC將被用于在流程工業(yè)，但不一定會(huì)用于過(guò)程控制”。</p><p>　　幾家廠商顯然押注相反，

72、以下將介紹了PLC在過(guò)程優(yōu)化中的應(yīng)用。瑞安，經(jīng)理，市場(chǎng)營(yíng)銷(xiāo)，艾倫-布拉德利可編程控制理學(xué)系。各種類(lèi)型的PLC越來(lái)越多地使用于各個(gè)行業(yè)，如食品，化工，石油等。</p><p>　　雖然有人擔(dān)心，來(lái)自不同供應(yīng)商的PLC之間缺乏兼容性，連接在末端的輸入/輸出是凌亂的，有些人認(rèn)為輸入/輸出端應(yīng)該是通有的。葛凡斯希望能做到這一點(diǎn)，用一根靈巧的輸入/輸出線把各個(gè)獨(dú)立的I / O廠家拉攏在一起。</p><

73、p>　　很多人說(shuō)I/O是一個(gè)高價(jià)值的項(xiàng)目，PLC的制造者總是希望保持其專(zhuān)有性。墾捷那特說(shuō)：“ I/O將是一個(gè)不成比例的硬件銷(xiāo)售，當(dāng)然每個(gè)PLC的廠家是要設(shè)法保護(hù)其技術(shù)的?！闭蛉绱?，他說(shuō)PLC的制造商將不會(huì)把通用的輸入/輸出系統(tǒng)賣(mài)給其他廠商?！叭绻覀冮_(kāi)始銷(xiāo)售這種產(chǎn)品” 捷那特說(shuō)，“我們還制造什么？” </p><p>　　隨著更多智能I/O的出現(xiàn)，薩爾認(rèn)為這將導(dǎo)致來(lái)自不同廠家的I/O之間有更多的不同之處。

74、“輸入/輸出變得更加智能化，并成為該系統(tǒng)的一部分，”他說(shuō)， “這真的是很難界定哪一個(gè)是輸入/輸出設(shè)備，哪一個(gè)是中央處理器，它真正開(kāi)始了分布式處理過(guò)程?，F(xiàn)在，為了使這種分布式處理能夠工作，如果你愿意，CPU也同樣可以納入制度作為I/O” 。</p><p>　　然而不同的PLC可能會(huì)繼續(xù)使用專(zhuān)有的I/O ，幾家廠商能夠把它們的輸入/輸出IBM個(gè)人電腦兼容的設(shè)備連接起來(lái)。艾倫-布拉德利，古爾德，辛辛那提米拉克龍已經(jīng)有

75、了按這樣的思路創(chuàng)辦一個(gè)電氣公司的計(jì)劃。</p><p>　　“和普通電腦之間在構(gòu)造上有內(nèi)在的差異” 瑞安說(shuō)，“可編程控制器有硬件構(gòu)造，幾乎每一個(gè)廠商都可以用可編程序控制器運(yùn)行梯形邏輯，并解決機(jī)器碼問(wèn)題” ，他說(shuō)其中根本的分歧是機(jī)器狀態(tài)，瑞安說(shuō)：“當(dāng)你關(guān)閉機(jī)器，或打斷運(yùn)行周期，或者你跳轉(zhuǎn)到另一個(gè)循環(huán)位置，可編程控制器就能記住機(jī)器的運(yùn)行狀態(tài)：什么定時(shí)器，什么計(jì)數(shù)器，有什么樣的鎖存狀態(tài)，而電腦卻做不到這些”。</