可編程邏輯控制器（plc）外文翻譯

1、<p>　　Programmable Logic Controllers</p><p>　　Programmable logic controller (plc) is a solid-state device used to control machine motion or process operation by means of a stored program. The PLC sends

2、output control signals and receives input signals through input/output (I/O) devices. A PLC controls outputs in response to stimuli at the inputs according to the logic prescribed by the stored program. The inputs are ma

3、de up of limit switches, pushbuttons, thunbwheels. Switches, pulses, analog signals, ASCLL serial data, and binary or BCD da</p><p>　　Programmable controllers were developed (circa in 1968) when General Moto

4、rs Corp, and other automobile manufacturers were experimenting to see if there might be an alternative to scrapping all their hardwired control panels of machine tools and other production equipment during a model change

5、over. This annual tradition was necessary because rewiring of the panels was more expensive than buying new ones.</p><p>　　The automotive companies approached a number of control equipment manufacturers and

6、asked them to develop a control system that would have a longer productive life without major rewiring, but would still be understandable to and repairable by plant personnel. The new product was named a “programmable co

7、ntroller”.</p><p>　　The processor part of the PLC contains a central processing unit and memory。The central processing unit (cpu) is the “traffic director” of the processor, the memory stores information. Co

8、ming into the processor are the electrical signals from the input devices, as conditioned by the input module to voltage levels acceptable to processor logic. The processor scans the state of I/o and updates outputs base

9、d on instructions stored in the memory of the plc. For example, the processor may be programm</p><p>　　The output device, such as a solenoid or motor starter, is wired to output module’s terminal, and it rec

10、eives its shift signal from the processor, in effect, the processor is performing a long and complicated series of logic decisions. The PLC performs such decisions sequentially and in accordance with the stored program.

11、Similarly, analog I/O allows the processor to make decisions based on the magnitude lf a signal. Rather than just if it is on or off. For example, The processor may be programm</p><p>　　Because a PLC is “sof

12、tware based”, its control logic functions can e changed by reprogramming its memory. Keyboard programming devices facilitate entry of the revised program, which can be designed to cause an existing machine or process to

13、operate in a different sequence or to respond to different levels of, or combinations of stimuli. Hardware modifications are needed only if additional, changed, or relocated input/output devices are involved. </p&g

14、t;<p>　　All programmable controllers consist of the basic functional blocks shown in Figure 10.1. We will examine each block to understand the relationship to the control system. First we looked at the center, as

15、it is the heart of the system. It consists of a microprocessor, logic memory for the storage of the actual control logic, storage or variable memory for use with data that will ordinarily change as a function of the cont

16、rol program execution, and a power supply to provide electrical power for t</p><p>　　An adaptive control system is one whose parameters are automatically adjusted to compensate for corresponding variations i

17、n the properties of the process. The system is, in a word, “adapted” to the needs of the process. Naturally there must be some criteria on which to base an adaptive program. To specify a value for the controlled variable

18、 is not enough-adaption is not required to meet this specification. Some “objective function” of the controlled variable must be specified in addition. It is </p><p>　　可編程邏輯控制器（PLC）</p><p>　　可編程

19、邏輯控制器（PLC）是一種固態(tài)電子裝置，它利用已存入的程序來(lái)控制機(jī)器的運(yùn)行或工藝的工序。PLC通過(guò)輸入/輸出(I/O)裝置發(fā)出控制信號(hào)和接受輸入信號(hào)。PLC依據(jù)已存入程序所規(guī)定的邏輯控制輸出裝置響應(yīng)輸入裝置的激勵(lì)。輸入裝置由限位開(kāi)關(guān)、按鈕、手輪、開(kāi)關(guān)、脈沖、模擬信號(hào)、ASCII系列數(shù)據(jù)和來(lái)自于絕對(duì)位置解碼器的二進(jìn)制或BCD數(shù)據(jù)組成。輸出的是驅(qū)動(dòng)電磁線圈、電動(dòng)起動(dòng)器、繼電器、指示燈等終端設(shè)備的電壓或電流電平。其他輸出裝置包括模擬裝置、數(shù)字

20、BCD顯示、ASCII兼容裝置、伺服變速驅(qū)動(dòng)器、甚至計(jì)算機(jī)。</p><p>　　當(dāng)通用汽車公司和其他制造商們正在試驗(yàn)看能否有另一種方法來(lái)銷毀型號(hào)轉(zhuǎn)變過(guò)程中機(jī)床的所有布線控制面板各其他生產(chǎn)設(shè)備時(shí)，PLC被研制成了（大約在1968年）。這種年度例行工作是必要的，因?yàn)榭刂泼姘宓闹匦虏季€比購(gòu)買新的控制面板要貴得多。</p><p>　　汽車公司與許多控制設(shè)備制造商打交道，請(qǐng)他們開(kāi)發(fā)一個(gè)控制系統(tǒng)，

21、這個(gè)系統(tǒng)要有較長(zhǎng)的生產(chǎn)壽命而無(wú)須主要線路重新布線，并且能被工廠人員所理解和維修。這個(gè)新系統(tǒng)被稱作“可編程控制器”。</p><p>　　PLC的處理器部分由中央處理器和存儲(chǔ)器組成。中央處理器（CPU）是處理器的“交通控制器”存儲(chǔ)器存信息。從輸入裝置來(lái)的電信號(hào)進(jìn)入處理器后，經(jīng)輸入模塊整理成處理器邏輯單元接受的電壓電平。處理器監(jiān)測(cè)I/O的狀態(tài)，然后依據(jù)儲(chǔ)存在PLC存儲(chǔ)器中指令更新輸出。例如，處理器可被編程以便當(dāng)連接限

22、位開(kāi)關(guān)的輸入位置時(shí)（限位開(kāi)關(guān)閉合），連在輸出模塊上的輸出裝置被接通，例如，這個(gè)輸出裝置可以是電磁線圈。處理器通過(guò)存儲(chǔ)器記錄下這個(gè)指令并與每次檢測(cè)相比較以確定限位開(kāi)關(guān)是否真的閉合。如果閉合，處理器通過(guò)接通輸出模塊接通電磁線圈。</p><p>　　諸如電磁線圈或電動(dòng)起動(dòng)機(jī)之類的輸出裝置被連接到輸出模塊的接線上，并從處理器接受它的位移信號(hào)。實(shí)際上，處理器在完成一系列長(zhǎng)而復(fù)雜的邏輯判斷。PLC按順序并根據(jù)存儲(chǔ)的程序來(lái)執(zhí)

23、行這樣的判斷。同樣地，模擬I/O裝置允許處理器依據(jù)信號(hào)的大小而不是其接通或關(guān)閉來(lái)做判斷。例如，處理可被編程為根據(jù)鍋爐實(shí)際溫度（模擬輸出）。這通常是用處理器的內(nèi)置PID（比例，積分、微分）能力來(lái)實(shí)現(xiàn)的。</p><p>　　因?yàn)镻LC是“基于軟件的”其控制邏輯功能可通過(guò)對(duì)存儲(chǔ)器再編程而改變。鍵盤(pán)編程裝置使修改的程序的輸入更方便，該程序可以被設(shè)計(jì)成使現(xiàn)有機(jī)器或工序以不同順序運(yùn)行，或響應(yīng)不同水平的激勵(lì)或激勵(lì)組合。只有當(dāng)

24、涉及到附加的、更改的或重新定位的輸入/輸出裝置時(shí)，才需要個(gè)性硬件。</p><p>　　可編程控制起都包含了基本的功能模塊，為了理解控制系統(tǒng)的關(guān)系，我們將檢查一下每一個(gè)模塊。首先，我們看一下中心，它是系統(tǒng)的心臟。中心包括微處理器、存儲(chǔ)當(dāng)前控制邏輯的邏輯存儲(chǔ)器、存儲(chǔ)常變量數(shù)據(jù)的變量存儲(chǔ)器，中西部分具有控制程序執(zhí)行和為微處理器與存儲(chǔ)器提供電力的功能。接著是I/O模塊，它的功能是為CPU提供控制水平信號(hào)，并把他們轉(zhuǎn)化為

25、適合連接工廠級(jí)別的傳感器和調(diào)節(jié)器的標(biāo)準(zhǔn)電壓和電流。I/O類型可以是數(shù)字信號(hào)、模擬信號(hào)或是應(yīng)用于某一定特定應(yīng)用的“智能”I/O。程序員通常僅需編寫(xiě)程序，而不需要考慮程序在系統(tǒng)中的運(yùn)行。他也可以用來(lái)發(fā)現(xiàn)并修理系統(tǒng)故障，在檢查系統(tǒng)故障的確切原因發(fā)面是個(gè)很有用的設(shè)備。在這里提到的設(shè)備代表了與I/O連接的各種傳感器和調(diào)節(jié)器，它門(mén)是系統(tǒng)的手臂、腿、眼睛和耳朵，其中包括按鈕、限制開(kāi)關(guān)、行程開(kāi)關(guān)、光敏元件、熱電偶、位置傳感器，作為輸入的讀卡機(jī)、標(biāo)燈、顯

26、示設(shè)備、發(fā)動(dòng)機(jī)、DC和AD驅(qū)動(dòng)器、螺線管和作為輸出的打印機(jī)。</p><p>　　適應(yīng)性控制系統(tǒng)是一種自動(dòng)調(diào)整其參數(shù)以補(bǔ)償過(guò)程特性的相應(yīng)變化的系統(tǒng)。簡(jiǎn)而言之，該系統(tǒng)可以“適應(yīng)”過(guò)程的需要。當(dāng)然，必須有一些作為適應(yīng)程序依據(jù)的原則。為被調(diào)量規(guī)定一個(gè)數(shù)值（即設(shè)定值）是不夠的，因?yàn)橐獫M足這一指標(biāo)。不僅需要適應(yīng)性控制。還必須另外規(guī)定被調(diào)量的某種“目標(biāo)函數(shù)”。這是一個(gè)決定需要何種特殊形式的適應(yīng)性控制的函數(shù)。一個(gè)給定過(guò)程的目標(biāo)

27、函數(shù)可能是被調(diào)量的衰減度。因而，實(shí)質(zhì)上有兩個(gè)回路，一個(gè)回路靠被調(diào)量操作，另一個(gè)則依賴其衰減度。由于衰減度標(biāo)志著回路動(dòng)態(tài)增益，因此這種系統(tǒng)被稱為動(dòng)態(tài)適應(yīng)性系統(tǒng)。也有可能為一個(gè)過(guò)程規(guī)定一個(gè)靜態(tài)增益的目標(biāo)函數(shù)。為這種指標(biāo)而設(shè)計(jì)的控制系統(tǒng)就是靜態(tài)適應(yīng)性系統(tǒng)。實(shí)際上，這兩種系統(tǒng)之間幾乎不存在相似，以至它們?cè)谕幻Q“適應(yīng)性”之下，它們的分類已經(jīng)引起了許多混淆。要指出的是，第二個(gè)區(qū)別并非是目標(biāo)函數(shù)，而是關(guān)于如何實(shí)現(xiàn)適應(yīng)性控制的機(jī)理問(wèn)題。如果對(duì)于過(guò)程