外文翻譯--可編程控制器

1、<p><b>　　電子與信息工程學(xué)院</b></p><p>　　本科畢業(yè)論文(設(shè)計(jì))</p><p>　　外 文 文 獻(xiàn) 翻 譯</p><p>　　譯文題目： Programmable logic controllers </p><p>　　

2、Hardware, software architecture </p><p>　　學(xué)生姓名： 吳凡 </p><p>　　專 業(yè)： 電氣工程及其自動(dòng)化 </p><p>

3、　　指導(dǎo)教師： 李東京 </p><p>　　2012年12月 </p><p>　　Programmable logic controllers:</p><p>　　Hardware, software architecture</p><p>　　Many respect

4、s, the architecture of the programmable logic controller (PLC) resembles a general-purpose computer with specialized input/output (I/O) modules. However, some important characteristics distinguish a PLC from a general-pu

5、rpose computer. Most important, a PLC is much more reliable, designed for a mean time between failures measured in years. Second, a PLC can be placed in an industrial environment with its substantial amount of electrical

6、 noise, vibration, extreme temperatures, and hum</p><p>　　Basic PLC hardware architecture</p><p>　　The basic architecture of a PLC consists of main components-the processor module, the power sup

7、ply, and the I/O modules. The processor module consists of the central processing unit (CPU) and memory. In addition to a microprocessor, the CPU also contains at least an interface to a programming device and may contai

8、n interfaces to remote I/O and other communication networks. The power supply is usually a separate module, and the I/O modules are separate from the processor. The types of I/O modules</p><p>　　Depending on

9、 the amount of I/O and the particular PLC processor, the I/O modules may be in the same chassis as the processor and/or in one or more other chassis. Up until the late 1980s, the I/O modules in a typical PLC system were

10、in chassis separate from the PLC processor. In the more typical present-day PLC, some of the I/O modules are present in the chassis that contains the processor. Some PLC systems allow more than one processor in the same

11、chassis. Smaller PLCs are often mounted on a DIN</p><p>　　Basic software, memory architecture (IEC 61131-3)</p><p>　　The IEC 61131-3 standard defines a memory and program model that follows mode

12、rn software engineering concepts. This model incorporates such features as top-down design, structured programming, hierarchical organization, formal software interfaces, and program encapsulation. Fortunately, extensive

13、 training in software engineering techniques is not necessary to become a proficient programmer. If fully implemented, the model is reasonably complicated. The main disadvantages of the model are its com</p><p

14、>　　The overall IEC 61131-3 memory pro-gram and memory model are described. (For various implementations of the standard, visit www.isa.org/link/Erickson_PLC.) The IEC 61131-3 memory model (what the standard calls the

15、software model) is layered-each layer hides many of the features of the layers beneath. Each of the main elements is now described.</p><p>　　The configuration is the entire body of software (program and data

16、) that corresponds to a PLC system. Generally, a configuration equates with the program and data for one PLC. In large complex systems that require multiple cooperating PLCs, each PLC has a separate configuration. A conf

17、iguration communicates with other IEC configuration s within the control system through defined inter-faces, called access paths. The choice of the term configuration conflict with the historic use of this term in </p

18、><p>　　A resource provides the support functions for the execution of programs. One or more resources constitute a configuration. Normally, a resource exists within a PLC, but it may exist within a personal com

19、puter to support program testing. One of the main functions of a resource is to provide an interface between a program and the physical I/O of the PLC.</p><p>　　A program generally consists of an interconnec

20、tion of function blocks, each of which may be written in any of the IEC languages. A function block or program is also called a program organization unit. In addition to the function blocks, the program contains declara

21、tions of physical inputs/outputs and any variables local to the program. A program can read and write to I/O channels, global variables, and communicate with other programs. Provide the means to transfer information betw

22、een con?gurati</p><p>　　parts of a program.</p><p>　　A task controls one or more programs and/or function blocks to execute. The execution of a program implies that all </p><p>　　of

23、 the function blocks in the program are processed once. The execution of a function block implies that all of the software elements of the function block are processed once. There are no implied mechanisms for program ex

24、ecution. In order for a program to be executed, it must be as-signed to a task, and the task must be con?gured to execute continuously, periodically, or with a trigger.</p><p>　　Variables are declared within

25、 the different software elements of the model. A local variable is defined at the software element and can only be accessed by the software element. Local variables can be defined for the function block, program, resourc

26、e, or con?guration.</p><p>　　A global variable defined for a con?guration, resource, or program is accessible to all elements contained in it. For example, a global con?guration variable is accessible to all

27、 software elements in the con?guration. A global program variable is accessible to all function blocks in the program.</p><p>　　Directly represented variables are memory and I/O locations in the PLC. IEC 611

28、31-3 defines formats for references to such data. However, many implementers of the standard use their own formats, which are not consistent with the IEC standard.</p><p><b>　　外文翻譯</b></p>

29、<p>　　在很多方面，可編程控制器的結(jié)構(gòu)就像一臺(tái)擁有特殊輸入、輸出模塊的通用型電腦。然而普通電腦相比有以下幾個(gè)顯著特點(diǎn)。最重要的是，PLC更可靠平均故障率很低。第二個(gè)方面，PLC可以在惡劣的條件下工作，如大量的電噪聲，震動(dòng)，極限的溫度，濕度。第三個(gè)方面，PLC在工廠設(shè)施中更容易穩(wěn)定。</p><p>　　PLC的基本硬件結(jié)構(gòu)</p><p>　　PLC的基本結(jié)構(gòu)有以下幾個(gè)主要

30、模塊——處理器模塊，電源模塊和輸入輸出模塊處理器模塊由中央處理器單元和存儲(chǔ)器組成。除此之外微處理器即CPU也至少包含編程接口，有的甚至含有I/O擴(kuò)展口和其他通訊網(wǎng)絡(luò)。電源部分通常是獨(dú)立的，而I/O模塊則與處理器分離，I/O模塊的形式有數(shù)字量和模擬量，特殊的模塊有運(yùn)動(dòng)控制模塊和高速計(jì)數(shù)器。工業(yè)設(shè)備就與I/O模塊相連。</p><p>　　根據(jù)I/O口的數(shù)量和PLC處理器的特點(diǎn)，I/O模塊可能與PLC在同一個(gè)底架或多

31、個(gè)底架中。直到19世紀(jì)80年代后期，I/O模塊和處理器分離在一個(gè)典型的PLC系統(tǒng)中。在如今典型的PLC中，有些I/O模塊也在包含處理器的底架中出現(xiàn)。有些PLC系統(tǒng)允許不止一個(gè)的處理器在一個(gè)底架中。小型PLC通常固定在導(dǎo)軌上最小的PLC包含電源，處理器，和所有I/O口在一個(gè)包裝盒中。有些微型PLC還包含內(nèi)嵌處理器接口。對(duì)于很多微型PLC來說，I/O口的數(shù)目是有限的和不可擴(kuò)展的。</p><p>　　基本軟件，存儲(chǔ)器

32、構(gòu)造</p><p>　　IEC 61131-3標(biāo)準(zhǔn)定義了存儲(chǔ)器單元和程序單元所遵循的現(xiàn)代軟件工程概念。該模型包括自上而下的設(shè)計(jì)，結(jié)構(gòu)化程序設(shè)計(jì)，分層組織，標(biāo)準(zhǔn)軟件接口程序簡述等特點(diǎn)。幸運(yùn)的是，想成為一名熟練的程序員，廣泛的軟件工程培訓(xùn)并不是必須的。如果完全應(yīng)用，那該模型將會(huì)相當(dāng)?shù)膹?fù)雜。該模型的與早期的PLC相比最主要的缺點(diǎn)是相對(duì)要復(fù)雜些。</p><p>　　關(guān)于存儲(chǔ)器模型已全部介紹完。

33、IEC 61131-3存儲(chǔ)器模型是每個(gè)層所隱藏的功能的最下面。到此關(guān)于PLC內(nèi)部的結(jié)構(gòu)已經(jīng)介紹完全。</p><p>　　一個(gè)完整的程序通常由內(nèi)部聯(lián)系的功能塊組成，它們可以以任意一種IEC語言寫成。一個(gè)功能塊程序也稱為程序組織單元。除了功能塊之外，程序也包括聲明語言。一個(gè)程序可以通過I/O通道與其他程序通信。提供通道與各結(jié)構(gòu)進(jìn)行交流。任務(wù)控制程序或某部分程序的執(zhí)行。</p><p>　　一

34、個(gè)任務(wù)控制一個(gè)或多個(gè)功能圖執(zhí)行。每個(gè)功能圖只執(zhí)行一次。一個(gè)程序要想執(zhí)行，必須被任務(wù)標(biāo)明，而且任務(wù)必須連續(xù)執(zhí)行，或有條件觸發(fā)。</p><p>　　變量在不同的軟件模型中聲明。一個(gè)在軟件元素定義的局部變量只能在軟件元素中使用。局部變量可以在功能圖，程序，結(jié)構(gòu)中定義。</p><p>　　一個(gè)全局變量可以被所有包含在內(nèi)的元素訪問。例如，一個(gè)全局組織變量可以被所有在結(jié)構(gòu)中的軟件元素訪問。一個(gè)全局