plc畢業(yè)設計外文翻譯3

1、<p><b>　　學校名稱</b></p><p><b>　　外 文 翻 譯</b></p><p>　　專 業(yè)： </p><p>　　班級學號： </p><p>　　學生姓名：

2、 </p><p>　　指導教師： </p><p><b>　　二〇一一年六月</b></p><p><b>　　學校名稱</b></p><p><b>　　本科生畢業(yè)設計</b></p><p>　　

3、原文1：Programmable logic controllers</p><p>　　譯文1：可編程邏輯控制器</p><p>　　原文2：Foundation of PLC</p><p><b>　　譯文2：PLC基礎</b></p><p><b>　　專業(yè)班級：</b></p>

4、;<p><b>　　學生姓名：</b></p><p><b>　　指導教師：</b></p><p><b>　　學 院：</b></p><p><b>　　2011年 6月</b></p><p><b>　　原文1：

5、 </b></p><p>　　Programmable logic controllers</p><p>　　Programmable logic controller(PLC) is eight 10- Year on behalf new generation industry that develop the control equip, and is an auto

6、matic control, calculator with the thing that the correspondence technique combine together, and is a the spot equipments for exclusively used foring the industry production line controling. Make the PLC there is charact

7、eristics of obvious oneself on the design with the long- term and continuous that circulate because of the special of the complexity, usage environ</p><p>　　A programmable logic controller(PLC) is a solid-st

8、ate devide used to control machine motion or process operation by means of a stored program. The PLC sends output control signals and receives input signals through input/output (I/O) devices.A PLC controls outputs in re

9、sponse to stimuli at the inputs according to the logic prescribed by the stored program.The inputs are made up of limit switches,pushbuttons,thumbwheels, switches,pulses,analog signals,ASCII serial data,and binary or BCD

10、 data from</p><p>　　Programmable controllers were developed(circa in 1968) when General Motors Corp,and other automobile manufacturers were experimenting to see if there might be an alterantive to scrapping

11、all their hardwired control panels of machine tools and other production equipment during a model changeover.This annual tradition was necessary because rewiring of the panels was more expensive than buying new oens.<

12、/p><p>　　The automotive companies approached a number of control equipment manufacturers and asked them to develop a control system that would have a longer productive life without major rewiring,but would stil

13、l be understandable to and repairable by plant personnel.The new product wa namd a“programmable controller”． </p><p>　　The processor part of the PLC contains a central processing unit and memory.The central

14、processing unit(CPU) is the“trafficdirector”of the processor,the memory stores information.Coming into the processor are the electrical signals from the input devices，as conditioned by the input module to voltage levels

15、acceptable to processor logic．The processor scans the state of I／O and updates outputs based on instructions stored in the memory of the PLC．For example，the processor may be programmed so that</p><p>　　The o

16、utput device, such as a solenoid or motor stater,is wired to an output mofule’s terminal,and itreceives its shift signal from the processor, in effect the peocessor is performing a long and complicated series of logic de

17、cisions. The PLC performs such decisions sequentially and in accordance with the stored program.similarly, analog I/O allows the processor to make decisions based on the magnitude of a signal, rather than just if is on o

18、r off.For example,the processor may be programmes toenc</p><p>　　Proper power to the programmable controller is critical. Today’s systems are available in a wide variety of electrical configurations. Virtual

19、ly all are designed for use in single-phase power systems, and most are now beginning to be offered with the optional ability to operate in a DC supply environment. AC designs are offered in either single voltage supplie

20、s, such as 115 or 230V AC; while some can be configured as either through a selection made on the power supply. Proper grounding of the po</p><p>　　Even the best of today' s well-designed and manufacture

21、d programmable controllers require occasional preventative maintenance and repair. This section looks at some of the tools provided by the manufacturer and techniques for general maintenance.Most of the medium- and large

22、-sized programmable controller systems available today are designed to be maintained by individuals with a wide variety of skills, without the benefit of in-depth formal training of this piece of equipment. This is accom

23、plish</p><p>　　The modular design and diagnostic indicators are, of course, important, but would be quite useless without well designed documentation provided by the manufacturer for the programmable control

24、ler system in question. Proper documentation will have sections dedicated to each major subsystem including CPU, I/O, and programming device. Each should explain in depth the stop-by-stop inspection of the system. All po

25、ssible combinations of failure mode should be listed, along with suggested actions for r</p><p>　　Because a PLC is “software based”, its control logic functions can be changed by reprogramming its memory. Ke

26、yboard programming devices facilitate entry of the revised program, which can be designed to cause an existing machine or process to operate in a different sequence or to respond to different levels of, or combinations o

27、f stimuli .Hardware modifications are needed only if additional, changed, or relocated input/output devices are involved.</p><p>　　Programmable controller memory is formatted into bits, bytes, and words of m

28、emory. A bit is a single storage element for either a zero or a one. A byte consists of eight bits, and a word (normally) consists of 16 bits, or two bytes. Some systems still use a word length of eight bits, but most ha

29、ve adopted a 16 bit word, even though they may use an 8 bit microprocessor.</p><p>　　Depending on the specific design of the programmable controller, it will have a stated memory capacity. This is an indicat

30、ion, although not the only one, of the capability and power of the system. Medium and large controllers are normally expandable from one memory size to their maximum size. Small controllers are normally fixed in their me

31、mory size. Size of the memory capacity must be examined relative to the word size ( 8 bit or 16 bit) and utilization. While it is clear that twice the informa</p><p>　　In fine, PLC conduct and actions the sp

32、ot control equipments, can dependable，accurately complete the control the operation, and can pass with upper grade work machine correspondence, constitute the distribute type the system to complete to control the industr

33、y equip. system control request, is a modern industry control the inside compare forerunner’s control project, and apply the foreground to is extensive.</p><p><b>　　譯文1：</b></p><p>&

34、lt;b>　　可編程邏輯控制器</b></p><p>　　可編程邏輯控制器（PLC）是八十年代發(fā)展起來的新一代工業(yè)控制裝置，是自動控制、計算機和通信技術相結合的產(chǎn)物，是一種專門用于工業(yè)生產(chǎn)過程控制的現(xiàn)場設備。由于控制對象的復雜性，使用環(huán)境的特殊性和運行的長期連續(xù)性，使PLC在設計上有自己明顯的特點：可靠性高，適應性廣，具有通信功能，編程方便，結構模塊化。在現(xiàn)代集散控制系統(tǒng)中，PLC已經(jīng)成為一種

35、重要的基本控制單元，在工業(yè)控制領域中應用前景極其廣泛。</p><p>　　可編程邏輯控制器（PLC）是一種固態(tài)電子裝置，它利用已存入的程序來控制機器的運行或工藝的工序。PLC通過輸入/輸出（I/O）裝置發(fā)出控制信號和接受輸入信號。PLC依據(jù)已存入程序所規(guī)定的邏輯控制輸出裝置響應輸入裝置的激勵。輸入裝置由限位開關、按扭、手輪、開關、脈沖、模擬信號、ASCII系列數(shù)據(jù)和來自于絕對位置解碼器的二進制或BCD數(shù)據(jù)組成。

36、輸出的是驅(qū)動電磁線圈、電動起動機、繼電器、指示燈等終端設備的電壓或電流電平。其他輸出裝置包括模擬裝置、數(shù)字BCD顯示、ASCII兼容裝置、伺服變速驅(qū)動器、甚至計算機。</p><p>　　當通用汽車公司和其他制造商們正在實驗看能否有另一種方法來銷毀型號轉(zhuǎn)變過程中機床的所有布線控制面板和其他生產(chǎn)設備時，PLC被研制成了（大約在1968年）。這種年例行工作是必要的，因為控制面板的重新布線比購買新的控制面板要貴得多。&

37、lt;/p><p>　　汽車的處理器部分由中央處理器和存儲器組成。中央處理器（CPU）是處理器的“交通控制器”，存儲器存儲信息。從輸入裝置來的信號進入處理器后，經(jīng)輸入模塊整理成處理邏輯單元可以接受的電壓電平。處理器監(jiān)測I/O的狀態(tài)，然后依據(jù)存儲在PLC存儲器中指令更新輸出。例如，處理器可被編程以便當連接限位開關的輸入位真時（限位開關閉合），連在輸出模塊上的輸出裝置被接通，例如，這個輸出裝置可以是電磁線圈。處理器通過存

38、儲器記錄下這個指令并與每次檢測相比較以確定限位開關是否真正閉合。如果閉合。處理器通過接通輸出模塊接通電磁線圈。</p><p>　　諸如電磁線圈或電動起動機之類的輸出裝置被連接到輸出模塊的連接柱上，并從處理器接受它的位移信號。實際上，處理器在完成一系列長而復雜的邏輯判斷。PLC按順序并根據(jù)存儲的程序來執(zhí)行這樣的判斷。同樣地，模擬I/O裝置允許處理器依據(jù)信號的大小而不是其接通或關閉來做判斷。例如，處理器可被編程為根

39、據(jù)鍋爐實際溫度（模擬量輸入）與所示需溫度的比較來增加或減少流向鍋爐的蒸汽（模擬量輸出）。這通常是用處理器的內(nèi)置PID（比例、積分、微分）能力來實現(xiàn)的。</p><p>　　對于可編程序控制器來講一個好的電源是很重要的。當今的系統(tǒng)可以從很多途徑獲得電力配置。事實上，它們都被設計為用于單電源地系統(tǒng)，而且現(xiàn)在他們中地大多數(shù)還提供了可選擇在直流環(huán)境下操作的能力。交流電源被設計成用于提供點電壓的供應，如115v獲230v交

40、流電壓在安全安裝中要求良好的電源與地的連接。一些可編程序控制器的設計有從機架到表面金屬極和其它系統(tǒng)中元器件之間單獨的接地，所以在進行電氣安裝時，系統(tǒng)接地的電氣連接一定要小心。在一般應用中，一般要求提供24v或120v的直流電。這在得不到交流電的電氣安裝中是很普遍的，比如象在前一代的電氣配置中。而且交流是不可靠的，以及控制中的電力消退也被認為是不可接受的情況。</p><p>　　當今即使是設計最好的、非常出色的可

41、編程序控制器也需要定時的包煙與維修。這部分我們主要來了解一下由可編程序控制器生產(chǎn)廠家提供的一些維修工具及技術。大多數(shù)大、中型可編程序控制器系統(tǒng)均被設計成可以通過很多各種各樣方法進行單獨維修，但這樣就失去了對這部設備進行正規(guī)、深入培訓的好處。這些在設計中通過提供安裝在電路板上有件（所有的調(diào)節(jié)類型中均包含有電源的供應）服務的單獨的功能基準裝置已被完成。這種控制上的暢通對于良好的保養(yǎng)與維修是起決定性作用的。這樣就可以更好的檢查及更換被認為壞了

42、的單位設施。單位基準設施的好壞一般是通過檢查安裝在每個基準裝置前的LED指示器的指示來決定的。典型的指示器是依據(jù)設計及正在出問題的基準裝置的狀況來顯示開與關（亮與滅）。各種各樣的CPU及I/O端口單位設施都有各自的指示裝置用來顯示I/O端口控制通訊的狀態(tài)，存儲的完整性，電源供應的極限檢查，掃描的完整性以及其他等等。在未來的控制器甚至當今為數(shù)不多的系統(tǒng)設計中，控制器將會顯示英文信息提醒使用者或維修人員一些常見的錯誤及建議做法。</p

43、><p>　　當然，基準單位的設計及特征指示是很重要的，沒有生產(chǎn)廠家提供的好的有關存在問題的可編程序控制器的設計參考資料也沒有用的。好的參考資料將會含有專門用于每個輔助系統(tǒng)的部分，包括CPU、I/O端口即可編程設施。每一部分均會一步一步深入的講解系統(tǒng)的檢查。。它將會列出所有可能出現(xiàn)的問題及建議維修方法。這部分最常用到的是被認為壞了的單元的替換。用戶將被建議購買一套由廠家推薦的備用基準裝置用于系統(tǒng)出問題的時候。一般至少

44、有單獨一套一般至少有單獨一套CPU和可編程設施服務系統(tǒng)的備用設備，以及是系統(tǒng)所有I/O端口數(shù)量10%的備用I/O端口。</p><p>　　因為PLC是“基于軟件的”，其控制邏輯功能可通過對存儲器再編程而改變。鍵盤編程裝置使修改的程序的輸入更方便，該程序可以被設計成使現(xiàn)有機器或工序以不同順序運行，或響應不同水平的激勵或激勵組合。只有當涉及到附加的、更改的或從新定位的輸入/輸出裝置時，需要修改硬件。</p&g

45、t;<p>　　可編程序控制器存儲器的格式可以為位、字節(jié)和字。 一位為一個單獨的存儲元素，即1或0。一個字節(jié)由8位組成， 一個字（一般來說）由16位，兩個字節(jié)組成。有些系統(tǒng)采用8位組成一個字的格式，但大多數(shù)系統(tǒng)采用的是16位一個字，即使它們應用的為8位的微處理器。</p><p>　　由于特殊的設計，可編程序控制器一般都具有固定的容量。這是系統(tǒng)性能好壞的一個標志（當然不止這一個）。大中型控制器一般具

46、有存儲器擴展的能力，即將一個存儲器擴展到它的最大容量。小型控制器的存儲容量則為固定的。存儲容量應該以組成一個字的位數(shù)（8位或16位）和具體應用來衡量。顯然地，16位字的存儲器的存儲容量是8位字的兩倍，但為什么有的控制器可以比其他控制器更高效地利用存儲器卻鮮為人知。例如，一般一個外部聯(lián)接和它相關的地址要用8位字節(jié)來存儲。故它們要占用一個16位字。某些控制器進行同一種操作會采用比上述存儲容量大的存儲器或更多。在大型程序中，這種低效會越積越多

47、從而造成系統(tǒng)存儲器運用上的浪費。各種各樣的存儲器都需要進行仔細的分析以確定應用的高效性。在實際運用中要留出額外20%—40%的存儲容量用于修改和擴展。這種分析結合應用要求方面的技巧對于可編程序控制器的選擇也是很有幫助的。</p><p>　　總之， PLC作為現(xiàn)場控制設備，能夠可靠、準確地成控制操作，并且可以通過與上級工控機通信，組成分布式系統(tǒng)完成工業(yè)設備控制、控制要求，是現(xiàn)代工業(yè)控制中比較先進的控制方案，應用前

48、景廣泛。</p><p><b>　　原文2：</b></p><p>　　Foundation of PLC</p><p>　　Applying programmable controllers is as critical to the user, as is solving the problems that come with des

49、igning and operating efficient production processes. In fact, it is through its innovative applications that the programmable controller has excelled and attracted the large following it enjoys today. Continued developme

50、nt in the application area supported the evolution of certain features and capabilities that are common today. Now we will examine the current scope of programmable controll</p><p>　　We have seen a partial l

51、isting of programmable controller applications, and while it was anything but complete, it did give a good overall look at the breadth and variety of use that programmable controllers enjoy. These systems, with such a si

52、mple and low technology heritage, have come to be capable of performing tasks that were previously considered impossible to accomplish, or at least very difficult and at great expense. We will look at a survey of applica

53、tions by major industry groups, and </p><p>　　1 The Central Processing Unit</p><p>　　Although referred to as the brain of the system, the Central Processing Unit in a normal installation is the

54、unsung hero, buried in a control cabinet, all but forgotten.</p><p>　　2. Scan Techniques</p><p>　　By definition and design, the programmable controller is dedicated to the continuous, repetitive

55、 task of examining the system inputs, solving the current control logic, and updating the system outputs. This task is referred to as scanning (sometimes called sweeping),and is accomplished in slightly different ways in

56、 each manufacturer’s programmable controller.</p><p>　　3. I/O Modules</p><p>　　An I/O module is the entity within a computer responsible for the control of one or more external devices and for t

57、he exchange of data between those devices and main memory and /or CPU registers. Thus, the I/O module must have and interface internal to the computer (to the CPU and main memory) and an interface external to the compute

58、r (to the external device).</p><p>　　The major functions or requirements for an I/O module fall into the following categories:</p><p>　　Control and timing</p><p>　　CPU Communication

59、</p><p>　　Device Communication</p><p>　　Data Buffering</p><p>　　Error Detection</p><p>　　During any period of time, the CPU may communicate with one or more external de

60、vices in unpredictable patterns, depending on the program’s need for I/O. The internal resources, such as main memory and the system buys, must be shared among a number of activities including data I/O. Thus, the I/O fun

61、ction includes a control and timing requirement, to coordinate the flow of traffic between internal resources and external devices. For example, the control of the transfer of data from an external dev</p><p&g

62、t;　　(1) The CPU interrogates the I/O module to check the status of the attached device.</p><p>　　(2) The I/O module returns the device status.</p><p>　　(3) If the device is operational and ready

63、 to transmit, the CPU requests the transfer of data, by means of a command to the I/O module.</p><p>　　(4) The I/O module obtains a unit of data (e.g., 8 or 16 bits) from the external device.</p><

64、p>　　(5) The data are transferred from the I/O module to the CPU.</p><p>　　If the system employs a bus, then each of the interactions between the CPU and the I/O module involves one or more bus arbitration

65、s.</p><p>　　The preceding simplified scenario also illustrates that the I/O module must have the capability to engage in communication with the CPU and with the external device. CPU communication involves:&l

66、t;/p><p>　　Command Decoding: The I/O module accepts commands from the CPU. These commands are generally sent as signals on the control bus. For example, an I/O module for a disk drive might accept the following

67、 commands: READ SECTOR, WRITE SECTOR, SEEK track number, and SCAN record ID. The latter two commands each include a parameter that is sent on the data bus .</p><p>　　Data: Data are exchanged between the CPU

68、and the I/O module over the data bus.</p><p>　　Status Reporting: Because peripherals are so slow, it is important to know the status of the I/O module. For example, if an I/O module is asked to send data to

69、the CPU (read), it may not be ready to do so because it is still working on the previous I/O command. This fact can be reported with a status signal. Common status signals are BUSY and READY. There may also be signals to

70、 report various error conditions.</p><p>　　I/O Commands</p><p>　　To execute an I/O-related instruction, the CPU issues an address, specifying the particular I/O module and external device, and a

71、n I/O command. There are four types of I/O commands that an I/O module may receive when it is addressed by a CPU. They are classified as control, test, read, and write.</p><p>　　A control command is used to

72、activate a peripheral and tell it what to do. For example, a magnetic-tape unit may be instructed to rewind or to move forward one record. These commands are tailored to the particular type of peripheral device. </p&g

73、t;<p>　　A text command is used to test various status conditions associated with an I/O module and its peripherals. The CPU will want to know that the peripheral of interest is powered on and available for use. It

74、 will also want to know if the most recent I/O operation is completed and if any errors occurred.</p><p>　　A read command causes the I/O module to obtain an item of data from the peripheral and place it in a

75、n internal buffer .The CPU can then obtain the data item by requesting that the I/O module place it on the data bus. Conversely, a write command causes the I/O module to take an item of data (byte or word ) from the data

76、 bus and subsequently transmit that data item to the peripheral.</p><p>　　4 .Semiconductor main memory</p><p>　　In earlier computers , the most common form of random-access storage for computer

77、main memory employed an array of doughnut-shaped ferromagnetic loops referred to as cores. Hence, main memory was often referred to as core, a term that persists to this day. The advent of , and advantages, microelectron

78、ics has long since vanquished the magnetic core memory. Today, the use of semiconductor chips for main memory is almost universal. Key aspects of this technology are explored in this section.</p><p>　　All of

79、 the memory types that we will explore in this section are random access. That is , individual words of memory are directly accessed through wired-in addressing logic.</p><p>　　Table 3 lists the major types

80、of semiconductor memory. The most common is referred to as random-access memory (RAM). This is, of course, a misuse of the term, since all of the types listed in the table are random access. One distinguishing characteri

81、stic of RAM is that it is possible both to read data from the memory and to easily and rapidly write new data into the memory. Both the reading and writing are accomplished through the use of electrical signals.</p>

82、;<p>　　The other distinguishing characteristic of RAM is that it is volatile. A RAM must be provided with a constant power supply. If the power is interrupted, then the data are lost. Thus, RAM can be used only as

83、 temporary storage.</p><p>　　RAM technology has divided into two technologies: static and dynamic. A dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge

84、in a capacitor is interpreted as a binary 1 or 0. Because capacitors have a natural tendency to discharge, dynamic RAMs require periodic charge refreshing to maintain data storage. In a static RAM, binary values are stor

85、ed using traditional flip-flop logic-gate configurations (see Appendix A for a description of flip-flo</p><p>　　Both static and dynamic RAMs are volatile. A dynamic memory cell is simpler and hence smaller t

86、han a static memory cell. Thus, a dynamic RAM is more dense (smaller cells=more cells per unit area) and less expensive than a corresponding static RAM. On the other hand, a dynamic RAM requires the supporting refresh ci

87、rcuitry. For larger memories, the fixed cost of the refresh circuitry is more than compensated for by the smaller variable cost of dynamic RAM cells. Thus dynamic RAMs tend to be favore</p><p>　　In sharp con

88、trast to the RAM is the read-only memory (ROM). As the name suggests, a ROM contains a permanent pattern of data that cannot be changed. While it is possible to read a ROM , it is not possible to write new data into it .

89、 An important application of ROMs is microprogramming, discussed in Part IV. Other potential applications include</p><p>　　Library subroutines for frequently wanted functions</p><p>　　System pro

90、grams</p><p>　　Function tables</p><p>　　For a modest-sized requirement, the advantage of ROM is that the data or program is permanently in main memory and need never be loaded from a secondary s

91、torage device.</p><p>　　A ROM is created like any other integrated-circuit chip, with the data actually wired-in to the chip as part of the fabrication process. This presents two problems.</p><p&g

92、t;　　The data insertion step includes a relatively large fixed cost, whether one or thousands of copies of a particular ROM are fabricated.</p><p>　　There is no room for error. If one bit is wrong, the whole

93、batch of ROMs must be thrown out.</p><p>　　When only a small number of ROMs with a particular memory content is needed, a less expensive alternative is the programmable ROM (PROM). Like the ROM, the PROM is

94、nonvolatile and may be written into only once. For the PROM, the writing process is performed electrically and may be performed by a supplier or customer at a time later than the original chip fabrication. Special equipm

95、ent is required for the writing or “programming” process. PROMs provide flexibility and convenience. The ROM remains</p><p>　　Another variation on read-only memory is the read-mostly memory, which is useful

96、for applications in which read operations are far more frequent than write operations but for which nonvolatile storage is required. There are three common forms of read-mostly memory: EPROM. EEPROM, and flash memory. &l

97、t;/p><p>　　The optically erasable programmable read-only memory (EPROM) is read and written electrically, as with PROM. However, before a write operation, all the storage cells must be erased to the same initia

98、l state by exposure of the packaged chip to ultraviolet radiation. This erasure process can be performed repeatedly; each erasure can take as much as 20 minutes to perform. Thus, the EPROM can be altered multiple times a

99、nd, like the ROM and PROM, holds its data virtually indefinitely. For comparable </p><p>　　A more attractive form of read-mostly memory is electrically erasable programmable read-only memory (EEPROM). This i

100、s a read-mostly memory that can be written into at any time without erasing prior contents; only the byte or bytes addressed are updated. The write operation takes considerably longer than the read operation, on the orde