可編程控制器畢業(yè)論文外文翻譯

1、b：外文文獻(xiàn)及譯文system block diagrama programmable controller is a specialized computer.since it is a computer, it has all the basic component parts that any other computer has; a central processing unit,memory, input interfacing and output interfacing.a typical programmable controller block diagram is sho

2、wn in figure 1.figure 1 programmable controller block diagramthe central processing unit (cpu) is the control portion of the plc. it interprets the program commands retrieved from memory and acts on those commands.in present day plcs this unit is a microprocessor based system.the cpu is housed in th

3、e processor module of modularized systems.memory in the system is generally of two types; rom and ram.the rom memory contains the program information that allows the cpu to interpret and act on the ladder logic program stored in the ram memory.ram memory is generally kept alive with an on-board batt

4、ery so that ladder programming is not lost when the system power is removed. this battery can be a standard dry cell or rechargeable nickel-cadmium type. newer plc units are now available with electrically erasable programmable read only memory (eeprom) which does not require a battery.memory is als

5、o housed in the processor module in modular systems. input units can be any of several different types depending on input signals expected as described above.when power is applied to a programmable logic controller, the plcs operation consists of two steps: (1) update inputs and outputs and (2) solv

6、e the ladder.the first thing the plc does when it begins to function is update i/o.this means that all discrete input states are recorded from the input unit and all discrete states to be output are transferred to the output unit.register data generally has specific addresses associated with it for

7、both input and output data referred to as input and output registers.these registers are available to the input and output modules requiring them and are updated with the discrete data.since this is input/output updating, it is referred to as i/o . after the i/o update has been accomplished, the plc

8、 begins executing the commands programmed into it.these commands are typically referred to as the ladder diagram.the ladder diagram is basically a representation of the program steps using relay contacts and coils.the ladder is drawn with contacts to the left side of the sheet and coils to the right

9、.after the i/o update, the plc moves to the first rung of ladder logic.it solves the contact configuration to determine if the coil is to be energized or de-energized.it then energizes or de-energizes the coil.after this is accomplished, it moves to the left side of the next rung and repeats the pro

10、cedure.this continues until all rungs have been solved. when this procedure is complete with all rungs solved and all coils in the ladder set up according to the solution of each rung, the plc proceeds to the next step of its sequence, the i/o update.i/o updating occurs, each input point that is on

11、at that time will cause a 1 to be set at the bit address associated with that particular input.if the input is off, a 0 will be set into the bit address.memory in todays plcs is generally configured in 16 bit words.this means that one word of memory can store the states of 16 discrete input points.

12、therefore, there may be a number of words of memory set aside as the input and output image registers.at i/o update, the status of the input image register is set according to the state of all discrete inputs and the status of the output image register is transferred to the output unit. this transfe

13、r of informationtypically only occurs at i/o update.it may be forced to occur at other times in plcs which have an immediate i/o update command.this command will force the plc to update the i/o at other times although this would be a special case.at i/o update, the states of all coils which are desi

14、gnated as outputs are transferred from the output image register to the output unit and the states of all inputs are transferred to the input image register.note that any input changes that occur during the solution of the ladder are ignored because they are only recorded at i/o update time.the stat

15、e of each coil is recorded to the output image register as each rung is solved. however, these states are not transferred to the output unit until i/o update time.figure2 scan cyclethis procedure of i/o update and solving the ladder diagram and i/o update is referred to as scanning and is represente

16、d in figure 2.8. the period between one i/o update and the next is referred to as one scan.the amount of time it takes the plc to get from one i/o update to the next is referred to as scan time.scan time is typically measured in milliseconds and is related to the speed of the cpu and the length of t

17、he ladder diagram that has to be solved. the slower the processor or the longer the ladder diagram, the longer the scan time of the system.the speed atwhich a plc scans memory is referred to as scan rate.scan rate units are usually listed inmsec/k of memory being utilized for the program. as an exam

18、ple, if a particular plc has a rated scan rate of 8 msec/k and the program occupies 6k of memory, it will take the plc 48 msec to complete one scan of the program.譯文：系統(tǒng)框圖可編程控制器是一種專(zhuān)用的計(jì)算機(jī)。因?yàn)樗且慌_(tái)計(jì)算機(jī)，它就應(yīng)該具有其它計(jì)算機(jī)的基本組成部分：中央處理單元，存儲(chǔ)器，輸入接口和輸出接口。一個(gè)典型的可編程控制器框圖如圖1所示中央處理器輸入連續(xù)離散寄存器開(kāi)關(guān)、繼電接觸器等分壓器、反饋電壓等指輪開(kāi)關(guān)、編碼器等輸出連續(xù)離

19、散寄存器繼電器、燈等模擬顯示、控制電壓等數(shù)字顯示存儲(chǔ)器只讀存儲(chǔ)器隨機(jī)存儲(chǔ)器圖1可編程控制器 框圖中央處理單元（cpu）是plc的控制部分。它解釋來(lái)自存儲(chǔ)器的程序指令并且按這些指令執(zhí)行操作?，F(xiàn)在plc的中央處理單元是一個(gè)基于微處理器的系統(tǒng)，被置于模塊化系統(tǒng)的處理器模塊中，系統(tǒng)存儲(chǔ)器大致分為兩類(lèi)：只讀存儲(chǔ)器和隨機(jī)存儲(chǔ)器。只讀存儲(chǔ)器包含程序信息，通過(guò)這些程序信息，cpu可以解釋和執(zhí)行存儲(chǔ)在隨機(jī)存儲(chǔ)器中的梯形圖程序。隨機(jī)存儲(chǔ)器一般都有板上電源維持，這樣系統(tǒng)掉電時(shí)，梯形圖程序不會(huì)丟失。這種電源可以是標(biāo)準(zhǔn)的干電池或可充電的鎳-鎘電池。新型的plc存儲(chǔ)單元使用電可擦除可編程只讀存儲(chǔ)器（eeprom），這就不

20、需要專(zhuān)門(mén)的電源維持。內(nèi)存也設(shè)在模塊化系統(tǒng)中的處理器模塊內(nèi)。輸入單元有若干不同類(lèi)型，所用類(lèi)型根據(jù)前述輸入信號(hào)需求選擇。輸入部件可以接收多種不同電壓和電流等級(jí)的離散信號(hào)或模擬信號(hào)。可編程邏輯控制器上電后，其運(yùn)作包含兩個(gè)階段：（1）刷新輸入和輸出（2）解讀梯形圖。plc開(kāi)始運(yùn)作時(shí)的首要操作就是刷新i/o。這就意味著通過(guò)輸入單元，所有的離散輸入狀態(tài)被記錄，而且所有將要輸出的離散狀態(tài)被轉(zhuǎn)移到輸出單元。通常有一些特定地址來(lái)寄存數(shù)據(jù)，這些地址與輸入和輸出數(shù)據(jù)相關(guān)，稱(chēng)為輸入和輸出寄存器這些寄存器與輸入和輸出模塊相連并且通過(guò)離散數(shù)據(jù)來(lái)更新。由于這是輸入/輸出的更新，因而它被稱(chēng)為i/o刷新。當(dāng)i/o刷新時(shí)，如果輸

21、入點(diǎn)輸入的是“開(kāi)”信號(hào)，那么與之相聯(lián)的位地址內(nèi)容被置“1”。如果輸入點(diǎn)輸入的是“關(guān)”信號(hào)，那么相應(yīng)的位地址內(nèi)容被置“0”。現(xiàn)在，plc存儲(chǔ)器字長(zhǎng)大都是16位。這意味著，內(nèi)存的一個(gè)字可存儲(chǔ)16個(gè)離散輸入點(diǎn)的狀態(tài)信息。因而，內(nèi)存中可能會(huì)有一定數(shù)量的字被預(yù)留，作為輸入和輸出映像寄存器。在i/o刷新時(shí)，輸入映像寄存器的狀態(tài)根據(jù)所有離散輸入的狀態(tài)信息變化，輸出映像寄存器的狀態(tài)被送至輸出單元。這種狀態(tài)信息的轉(zhuǎn)變通常只發(fā)生在的i/o刷新階段。但是，在plc工作的其它時(shí)段，當(dāng)有i/o立即刷新命令時(shí)，狀態(tài)信息的轉(zhuǎn)變也可以被強(qiáng)制進(jìn)行。作為一種特殊情況，這條命令將會(huì)迫使plc在其它任何時(shí)候刷新i/o。輸入輸出刷新完

22、成后，plc開(kāi)始執(zhí)行編入的指令。這些指令通常稱(chēng)為梯形圖，該梯形圖基本上使用繼電器觸點(diǎn)和線圈編程。輸入輸出刷新完畢后，plc轉(zhuǎn)向梯形邏輯中的第一個(gè)階梯，處理接點(diǎn)元件，判定線圈將得電或失電，然后使線圈得電或失電。完成此操作后，plc轉(zhuǎn)向下個(gè)階梯，重復(fù)前面步驟，這樣持續(xù)到所有階梯被處理完畢。當(dāng)處理所有階梯的過(guò)程完畢，并且梯形圖中所有的線圈都已根據(jù)處理的每個(gè)階梯設(shè)定，那么plc就進(jìn)入到其下一個(gè)階段i/o刷新。i/o刷新階段，所有輸出線圈的狀態(tài)從輸出映像寄存器轉(zhuǎn)移到輸出單元，同時(shí)所有輸入狀態(tài)被轉(zhuǎn)移到輸入映像寄存器。注意，在處理梯形圖期間，輸入的任何變化 將被忽略，因?yàn)樗鼈冎挥性趇/o刷新階段才被記錄。在

23、處理每一階梯時(shí)，每個(gè)線圈的狀態(tài)將被記錄至輸出映像寄存器。然而，這些狀態(tài)直到i/o刷新階段才被轉(zhuǎn)移至輸出單元。這種i/o刷新、處理梯形圖再到i/o刷新的過(guò)程稱(chēng)為掃描，其描述如圖2.8。前一次i/o刷新和下次刷新之間的時(shí)段稱(chēng)為一次掃描。plc從前一次i/o刷新到下次刷新所用的時(shí)間稱(chēng)為掃描時(shí)間。掃描時(shí)間通常以毫秒為單位來(lái)衡量，而且掃描時(shí)間與cpu的運(yùn)行速度和所要處理的梯形圖的長(zhǎng)度有關(guān)。plc掃描存儲(chǔ)器的速度稱(chēng)為掃描速度。掃描速度單位通常為毫秒/k,程序正在使用的內(nèi)存。例如，如果某一plc掃描速度為8毫秒/k，程序占用8k的內(nèi)存 ，那么plc將會(huì)用48毫秒完成一次程序掃描。圖2 循環(huán)掃描.附錄c：參考

24、文獻(xiàn)及內(nèi)容簡(jiǎn)介【1】劉裁文.電梯控制系統(tǒng)m.北京:電子工業(yè)出版社，1996本文在已有的通用變頻器的基礎(chǔ)上，采用對(duì)電梯進(jìn)行控制，通過(guò)合理的選擇和設(shè)計(jì)，提高了電梯的控制水平，改善了電梯運(yùn)行的舒適感，使電梯達(dá)到較為理想的控制效果【2】唐勇奇，趙葵銀，汪超.電梯變頻調(diào)速plc控制的設(shè)計(jì)與實(shí)現(xiàn)j .湖南工程學(xué)院學(xué)報(bào).2000年02期.介紹了一種采用和變頻器控制的電梯控制系統(tǒng)，闡述了該系統(tǒng)中硬件和軟件設(shè)計(jì)方法，提高了電梯運(yùn)行的可靠性、舒適性和效率?！?】張燕賓.spwm變頻調(diào)速應(yīng)用技術(shù)m.機(jī)械工業(yè)出版社.2005. 本書(shū)首先深入淺出地講解了電力拖動(dòng)系統(tǒng)的工作要求、異步電動(dòng)機(jī)的主要理論和交直、交變頻器的基本原理，而