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1、学校名称外 文 翻 译专 业： 班级学号： 学生姓名： 指导教师： 二一一年六月学校名称本科生毕业设计原文1：Programmable logic controllers译文1：可编程逻辑控制器原文2：Foundation of PLC译文2：PLC基础专业班级：学生姓名：指导教师：学 院：2011年 6月原文1： Programmable logic controllersProgrammable logic controller(PLC) is eight 10- Year on behalf new generation industry that develop the control
2、 equip, and is an automatic 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 characteristics of obvious oneself on the design with the long- t
3、erm and continuous that circulate because of the special of the complexity, usage environment of the control object: The dependable is high, and the adaptability is wide, and have to correspond by letter the function, and weave the the convenience, construction mold piece . Gather the the control in
4、 the modern in the system, the PLC have already become a kind of importance of basic control unit, control the realm the inside in the industry applied the foreground is very and extensive. A programmable logic controller(PLC) is a solid-state devide used to control machine motion or process operati
5、on 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 response to stimuli at the inputs according to the logic prescribed by the stored program.The inputs are made up of limit switches,pushbuttons
6、,thumbwheels, switches,pulses,analog signals,ASCII serial data,and binary or BCD data from absolute position encoders.The outputs are voltage or current levers to drive end devices such as lolenids,motor staters,relays,lights,and so on.Other output devices such include analog devices,digital BCD dis
7、plays,ASCII compatible devices,servo variable-speed drives,and even computers.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 all their hardwired control panels
8、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.The automotive companies approached a number of control equipment manufacturers and asked them to develop a control sys
9、tem that would have a longer productive life without major rewiring,but would still be understandable to and repairable by plant personnel.The new product wa namd a“programmable controller” The processor part of the PLC contains a central processing unit and memory.The central processing unit(CPU) i
10、s 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 acceptable to processor logicThe processor scans the state of IO and updates outputs based on instruct
11、ions stored in the memory of the PLCFor example，the processor may be programmed so that if an input connected to a limit switch is true(1imit switch closed),then a corresponding output wired to an output module is to be energizedThis output might be asolenoid for exampleThe processor remembers this
12、command through its memory and compares on each scan to see if that limit is, in fact ,closed. If it is closed, the processor energizes the solenoid by turning on the output module.The output device, such as a solenoid or motor stater,is wired to an output mofules terminal,and itreceives its shift s
13、ignal from the processor, in effect the peocessor is performing a long and complicated series of logic decisions. 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, ra
14、ther than just if is on or off.For example,the processor may be programmes toencrease or decrease the steam flow to a boiler(analog output) based on a comparison of the actual temperature in the boiler(analog input) to the desired temperature. this is often performed by utilizing the built-in PID(pr
15、oportional,integral,derivative) capabilities of the processor.Proper power to the programmable controller is critical. Todays systems are available in a wide variety of electrical configurations. Virtually all are designed for use in single-phase power systems, and most are now beginning to be offer
16、ed with the optional ability to operate in a DC supply environment. AC designs are offered in either single voltage supplies, 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 power supply connection is required for a
17、 safe installation. Some programmable controller designs have individual grounding connections from rack to face- plates and other system components, so care must be taken to follow well electrical practice in system grounding during electrical installation. In certain applications, a 24 or 120 V DC
18、 power supply is required. This is common for installations that axe made where no AC power is available, such as remote electrical generation stations. It is also found where AC power is unreliable and where loss of control is considered an unacceptable situationEven the best of today s well-design
19、ed and manufactured 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-sized programmable controller systems available today are des
20、igned 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 accomplished in the design by providing individual modules of functionality installed in a chassis serviced from the front (all module types includ
21、ing power supplies). Front access is critical to proper maintenance. This allows easy inspection and replacement of the suspected bad module. Module health is determined by inspecting the LED indicators normally provided on the front of each module. Typical indicators will be on or off depending on
22、the design and individual condition of the module in question. Various CPU and I/O modules will have indicators showing I/O control communications status, memory integrity, power supply tolerance check, scan integrity, and others. On future controller designs, and even today on a few systems, it is
23、likely that English language messages will be displayed on the controller advising the user or maintenance personnel that a particular failure has occurred and recommended actions to take.The modular design and diagnostic indicators are, of course, important, but would be quite useless without well
24、designed documentation provided by the manufacturer for the programmable controller 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 repair. This will most often involve only the substitution of a re- placement board for the suspected failed unit. The user is urged to purchase a set of spare modules for the system in question as recommended by
26、the manufacturer. This is normally, at a minimum, a single replacement module for each CPU and programming device serviceable module, and spare I/O modules equal to 10% of the number in the system.Because a PLC is “software based”, its control logic functions can be changed by reprogramming its memo
27、ry. Keyboard 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 of stimuli .Hardware modifications are needed only if additional, changed,
28、or relocated input/output devices are involved.Programmable controller memory is formatted into bits, bytes, and words of memory. 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 u
29、se a word length of eight bits, but most have adopted a 16 bit word, even though they may use an 8 bit microprocessor.Depending on the specific design of the programmable controller, it will have a stated memory capacity. This is an indication, although not the only one, of the capability and power
30、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 memory 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
31、 twice the information can be stored in a 16 bit word than in an 8 bit word, it may not be immediately clear that some controllers utilize memory more efficiently than others. For example, a normally open contact and its associated reference address (e.g. Input 1), may use in 8 bit byte each for sto
32、rage. Combined, they consume one 16 bit word. Some controllers may use more memory than this for these instructions or others. In a large program, these inefficiencies can build on each other to cause a poor utilization of the system memory. A careful analysis of the various programmable controller
33、models is required to assess utilization efficiency. Normal practice calls for an additional 20% - 40% of memory size to be specified to allow for modifications and later expansion. This analysis, combined with knowledge of the application needs, will allow for an intelligent choice of programmable
34、controller.In fine, PLC conduct and actions the spot 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 industry equip. system control reques
35、t, is a modern industry control the inside compare forerunners control project, and apply the foreground to is extensive.译文1：可编程逻辑控制器可编程逻辑控制器（PLC）是八十年代发展起来的新一代工业控制装置，是自动控制、计算机和通信技术相结合的产物，是一种专门用于工业生产过程控制的现场设备。由于控制对象的复杂性，使用环境的特殊性和运行的长期连续性，使PLC在设计上有自己明显的特点：可靠性高，适应性广，具有通信功能，编程方便，结构模块化。在现代集散控制系统中，PLC已经成为
36、一种重要的基本控制单元，在工业控制领域中应用前景极其广泛。可编程逻辑控制器（PLC）是一种固态电子装置，它利用已存入的程序来控制机器的运行或工艺的工序。PLC通过输入/输出（I/O）装置发出控制信号和接受输入信号。PLC依据已存入程序所规定的逻辑控制输出装置响应输入装置的激励。输入装置由限位开关、按扭、手轮、开关、脉冲、模拟信号、ASCII系列数据和来自于绝对位置解码器的二进制或BCD数据组成。输出的是驱动电磁线圈、电动起动机、继电器、指示灯等终端设备的电压或电流电平。其他输出装置包括模拟装置、数字BCD显示、ASCII兼容装置、伺服变速驱动器、甚至计算机。当通用汽车公司和其他制造商们正在实验
37、看能否有另一种方法来销毁型号转变过程中机床的所有布线控制面板和其他生产设备时，PLC被研制成了（大约在1968年）。这种年例行工作是必要的，因为控制面板的重新布线比购买新的控制面板要贵得多。汽车的处理器部分由中央处理器和存储器组成。中央处理器（CPU）是处理器的“交通控制器”，存储器存储信息。从输入装置来的信号进入处理器后，经输入模块整理成处理逻辑单元可以接受的电压电平。处理器监测I/O的状态，然后依据存储在PLC存储器中指令更新输出。例如，处理器可被编程以便当连接限位开关的输入位真时（限位开关闭合），连在输出模块上的输出装置被接通，例如，这个输出装置可以是电磁线圈。处理器通过存储器记录下这个
38、指令并与每次检测相比较以确定限位开关是否真正闭合。如果闭合。处理器通过接通输出模块接通电磁线圈。诸如电磁线圈或电动起动机之类的输出装置被连接到输出模块的连接柱上，并从处理器接受它的位移信号。实际上，处理器在完成一系列长而复杂的逻辑判断。PLC按顺序并根据存储的程序来执行这样的判断。同样地，模拟I/O装置允许处理器依据信号的大小而不是其接通或关闭来做判断。例如，处理器可被编程为根据锅炉实际温度（模拟量输入）与所示需温度的比较来增加或减少流向锅炉的蒸汽（模拟量输出）。这通常是用处理器的内置PID（比例、积分、微分）能力来实现的。对于可编程序控制器来讲一个好的电源是很重要的。当今的系统可以从很多途径
39、获得电力配置。事实上，它们都被设计为用于单电源地系统，而且现在他们中地大多数还提供了可选择在直流环境下操作的能力。交流电源被设计成用于提供点电压的供应，如115v获230v交流电压在安全安装中要求良好的电源与地的连接。一些可编程序控制器的设计有从机架到表面金属极和其它系统中元器件之间单独的接地，所以在进行电气安装时，系统接地的电气连接一定要小心。在一般应用中，一般要求提供24v或120v的直流电。这在得不到交流电的电气安装中是很普遍的，比如象在前一代的电气配置中。而且交流是不可靠的，以及控制中的电力消退也被认为是不可接受的情况。当今即使是设计最好的、非常出色的可编程序控制器也需要定时的包烟与维
40、修。这部分我们主要来了解一下由可编程序控制器生产厂家提供的一些维修工具及技术。大多数大、中型可编程序控制器系统均被设计成可以通过很多各种各样方法进行单独维修，但这样就失去了对这部设备进行正规、深入培训的好处。这些在设计中通过提供安装在电路板上有件（所有的调节类型中均包含有电源的供应）服务的单独的功能基准装置已被完成。这种控制上的畅通对于良好的保养与维修是起决定性作用的。这样就可以更好的检查及更换被认为坏了的单位设施。单位基准设施的好坏一般是通过检查安装在每个基准装置前的LED指示器的指示来决定的。典型的指示器是依据设计及正在出问题的基准装置的状况来显示开与关（亮与灭）。各种各样的CPU及I/O
41、端口单位设施都有各自的指示装置用来显示I/O端口控制通讯的状态，存储的完整性，电源供应的极限检查，扫描的完整性以及其他等等。在未来的控制器甚至当今为数不多的系统设计中，控制器将会显示英文信息提醒使用者或维修人员一些常见的错误及建议做法。当然，基准单位的设计及特征指示是很重要的，没有生产厂家提供的好的有关存在问题的可编程序控制器的设计参考资料也没有用的。好的参考资料将会含有专门用于每个辅助系统的部分，包括CPU、I/O端口即可编程设施。每一部分均会一步一步深入的讲解系统的检查。它将会列出所有可能出现的问题及建议维修方法。这部分最常用到的是被认为坏了的单元的替换。用户将被建议购买一套由厂家推荐的备
42、用基准装置用于系统出问题的时候。一般至少有单独一套一般至少有单独一套CPU和可编程设施服务系统的备用设备，以及是系统所有I/O端口数量10%的备用I/O端口。因为PLC是“基于软件的”，其控制逻辑功能可通过对存储器再编程而改变。键盘编程装置使修改的程序的输入更方便，该程序可以被设计成使现有机器或工序以不同顺序运行，或响应不同水平的激励或激励组合。只有当涉及到附加的、更改的或从新定位的输入/输出装置时，需要修改硬件。可编程序控制器存储器的格式可以为位、字节和字。 一位为一个单独的存储元素，即1或0。一个字节由8位组成， 一个字（一般来说）由16位，两个字节组成。有些系统采用8位组成一个字的格式，
43、但大多数系统采用的是16位一个字，即使它们应用的为8位的微处理器。由于特殊的设计，可编程序控制器一般都具有固定的容量。这是系统性能好坏的一个标志（当然不止这一个）。大中型控制器一般具有存储器扩展的能力，即将一个存储器扩展到它的最大容量。小型控制器的存储容量则为固定的。存储容量应该以组成一个字的位数（8位或16位）和具体应用来衡量。显然地，16位字的存储器的存储容量是8位字的两倍，但为什么有的控制器可以比其他控制器更高效地利用存储器却鲜为人知。例如，一般一个外部联接和它相关的地址要用8位字节来存储。故它们要占用一个16位字。某些控制器进行同一种操作会采用比上述存储容量大的存储器或更多。在大型程序
44、中，这种低效会越积越多从而造成系统存储器运用上的浪费。各种各样的存储器都需要进行仔细的分析以确定应用的高效性。在实际运用中要留出额外20%40%的存储容量用于修改和扩展。这种分析结合应用要求方面的技巧对于可编程序控制器的选择也是很有帮助的。总之， PLC作为现场控制设备，能够可靠、准确地成控制操作，并且可以通过与上级工控机通信，组成分布式系统完成工业设备控制、控制要求，是现代工业控制中比较先进的控制方案，应用前景广泛。原文2：Foundation of PLCApplying programmable controllers is as critical to the user, as is
45、solving the problems that come with designing 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 development in the application area supported the
46、evolution of certain features and capabilities that are common today. Now we will examine the current scope of programmable controller applications, briefly look at the steps involved in implementing a system for a typical application, and consider some logical groupings of applications common today
47、, including basic, industry specific, and generic.We have seen a partial listing 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 simple a
48、nd 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 applications by major industry groups, and while some of the application areas are common to many of the groups, it provides a structured method to categorize the wide variety of applications. The structure will consist of two major groups-discrete part manufacturing and process-and several subgroups in each major group.1 The Central Processing Unit Although referred to as the brain
