基于PLC的电子计算器(内附中英文翻译)资料

电气工程学院课程设计说明书电气控制与PLC设计题目：电子计算器系别：电气工程年级专业： 12级检测学号： 121203021030学生姓名：滕禹铄指导教师：金梅教师职称：副教授电气工程学院《课程设计》任务书课程名称：电气控制与PLC基层教学单位：仪器科学与工程系指导教师：金梅学号121203021030 学生姓名滕禹铄（专业）班级检测一班设计题目电子计算器设计设计技术参数1.设计内容见附页（22）2.使用组态王实现上位控制3.公共实践（四层电梯）4.公共实践（邮件分拣）（选作）5.查阅资料（变频器）设计要求采用PLC进行设计。

画出系统图，采用梯形图编程，并给出相应的组态控制工程（附主画面）。

结合公共实践部分，完成设计说明书。

参考资料“电气控制”类图书及论文资料“可编程控制器”类图书及论文资料周次20周应完成内容分析设计要求、查资料、确定方案，设计梯形图、设计上位组态撰写课程设计说明书，答辩指导教师签字基层教学单位主任签字摘要可编程序控制器简称PLC，是微机技术与继电器常规控制技术相结合的产物，是在顺序控制器和微机控制器的基础上发展起来的新型控制器，是一种以微处理器为核心用作数字控制的专用计算机。

自1969年针对工业自动控制的特点和需要而丌发的第一台PLC问世以来，迄今己30多年，它的发展虽然包含了前期控制技术的继承和演变，但又不同于顺序控制器和通用的微机控制装置。

它不仅充分利用微处理器的优点来满足各种工业领域的实时控制要求，同时也照顾到现场电气操作维护人员的技能和习惯，摒弃了微机常用的计算机编程语言的表达方式，独具风格地形成一套以继电器梯形图为基础的形象编程语言和模块化的软件结构，使用户程序的编制清晰直观、方便易学，调试和查错都很容易。

用户买到所需PLC后，只需按说明书或提示，做少量的安装接线和用户程序的编制工作，就可灵活而方便地将PLC 应用于生产实践。

而且用户程序的编制、修改和调试不需要具有专门的计算机编程语言知识。

可编程控制技术简介1. 起源可编程控制器是60年代末在美国第一个出现的，当时叫可编程逻辑控制器PLC（Programmable Logic Controller），目的是用来取代继电器。

以执行逻辑判断、计时、计数等顺序控制功能。

提出PLC概念的是美国的通用汽车公司。

PLC的基本设计思想是把计算机功能完善、灵活、通用等优点和继电器控制系统的简单易懂、操作方便、价格便宜等优点结合起来，控制器的硬件是标准的、大家都能用的。

根据实际目标对象，将控制内容编成软件写入控制器的用户程序存储器里面,使控制器和被控对象方便的连接在一起。

70年代中期以后，PLC已广泛地使用微处理器作为中央处理器，输入输出模块和外围电路也都采用了中、大规模甚至超大规模的集成电路，这时的PLC已不仅仅只有简单逻辑判断功能，还同时具有数据处理功能、PID调节和数据通信功能。

国际电工委员会(IEC)颁布的可编程控制器标准草案中对可编程控制器作了如下的定义：可编程控制器是一种数字运算操作的电子系统，专门为在工业环境下应用而设计。

它采用了可编程序的存储器件，用来在其内部存储执行逻辑运算，顺序控制、定时、计数和算术运算等操作的命令，并通过数字式和模拟式的输入和输出口，控制各种类型的机械或生产进程。

可编程控制器及其有关外围设备，易于与工业控制系统联成一个整体，是易于扩充其功能的设计。

可编程控制器对用户来说，是一种没有接触点的设备，改变程序就能够改变生产工艺手续。

目前，可编程控制器已成为工厂自动化的非常强大的工具，得到了广泛的普及推广和应用。

可编程控制器是面向用户的专用工业控制计算机，具有许多明显的特点。

2.最初想法1968年，Richard E. Morley创造出了最新一代工业控制装置可编程逻辑控制器(PLC),现在，PLC 已经被广泛应用于工业领域，包括机械制造业、运输系统、化学过程设备、以及许多其他领域。

初期可编程控制器只是用一种类似于语言的软件逻辑于代替继电器硬件逻辑，并且使开发时间由6个月压缩到6天。

基于PLC全自动洗衣机系统设计Design of the PLC based full-automatic washing machine system可编程控制器programmable logic controller“PLC是一种专门为在工业环境下应用而设计的数字运算操作的电子装置。

它采用可以编制程序的存储器，用来在其内部存储执行逻辑运算、顺序运算、计时、计数和算术运算等操作的指令，并能通过数字式或模拟式的输入和输出，控制各种类型的机械或生产过程。

PLC及其有关的外围设备都应该按易于与工业控制系统形成一个整体，易于扩展其功能的原则而设计。

”"PLC is a specialized in industrial environment and design of the application of the electronic device digital computing operations. It USES can build programs used in its internal memory, storage to perform the logic operation, order processing, timing, counting and arithmetic operation instruction, and digital or analog through the input and output, the control of the various types of machinery orproduction process and its related. PLC peripheral devices should be easy and industrial control system according to form a whole, easy to expand its function principle and design."可编程控制器(PLC)是以计算机技术为核心的通用自动化控制装置,它的功能性强,可靠性高,编程简单,使用方便,体积小巧,近年来在工业生产中得到广泛的应用,被誉为当代工业自动化主要支柱之一。

许多不同过程的自动化，比如控制生产机械或工厂流水线，这些都是有可称为可编程逻辑控制器（PLC）的小型计算机来完成的。

可编程逻辑控制器是通用技术公司在1968年为了用电子控制器代接线的继电气系统而开发的。

随着可编程逻辑控制器的出现，集中控制工厂生产线的能力，尤其是在汽车工业上得到了重大的发展。

PLC的构架可编程逻辑控制器是一个无磁紧密型计算机，它包含了所有的必需的软件和连接程序的硬件接口。

他们通常用于自动化的控制应用。

（如：闭合回路控制）可以独立存在或者链接到分布的WorldFIP,MPI,PROFIBUS或者Ethernet..3-3A-1向我们展示了一个典型的PLC系统，它是创建在MIP和PROFIBUS上的。

一个典型的PLC组成由：●电源；●程序运行的CPU；●输入输出模块；●可选通信模块。

可用I/O模块支持很多的电气接口：●模拟模块（+/-10v,+/-1v,4-20mA,resistor.edc）；●温度测量模块(pt100,NI 100,etc)；●数字模块（±24V,220V,etc.）；●TTL模块（Beckhoff I/O模块，etc.）；●RS 232模块；●其他。

这些模块可以连接到PLC的内部总线上，也可以通过总线连接器和现场总线单元（如：PROFIBUS,WorldFIP or CAN）连接，并与其他PLC共享总线。

用户的硬件很难和PLC内部总线连接起来，解决的方案是使用特定接口卡（如：HMS的AnyBus卡）作为标准现场总线接口（如PROFIBUS,CAN和World FIP）继承用户硬件。

现在，PLC提供基于以太网的通信。

尽管基于TPC/IP和IEEE802.2,每个厂商的PLC协议不同。

因此，默认情况下，不同厂商的PLC不能通过以太网连接数据。

但是Schneider的PLC拥有接口库，可以用西门子的PLC实现RFC1006,也可以用OPC DX服务器，SCADA应用，或者特定接口卡，如APPLICOM one,作为网关。

英文The basic concepts of PLCPLC (Programmable Controller) is a computer in a family, is designed for industrial control applications manufactured. Early known as programmable logic control PLC (Programmable Logic Controller), referred to as PLC, which is mainly used to replace the relay logic control to achieve. As technology advances, the device's functionality has been greatly exceeded the scope of logic control, therefore, today, such a device known as programmable controllers, referred to as PC. However, in order to avoid a personal computer (Personal Computer) short confusion, it will be referred to as programmable logic controller PLC.PLC OriginIn the 60 years, automobile production line automatic control system are basically constituted by a relay control device. Each time the car was modified relay control devices are a direct result of the re-design and installation. With the development of production, car models update cycle becomes shorter, so that relay control devices often need tore-design and installation is very time-consuming, labor intensive, and costs expected, and even hindered the shorter update cycle. To change this situation, the U.S. General Motors Corporation in 1969, open tender, asking that the new control device to replace the relay control unit and made a tender 10 indicators, namely:1. Programming convenience, the site can modify the program;2. Easy maintenance, modular structure;3. Reliability is higher than relay control device;4. Smaller than relay control device;5. Data can be directly sent to the management computer;6. Costs can be competitive with the relay control device;7. Input can be AC 115V;8. Output AC 115V, 2A above, can directly drive solenoids, contactors, etc.;9. In the expansion, the original system as long as the small change;10. User program memory capacity can be expanded to at least 4K.In 1969, the U.S. Digital Equipment Corporation (DEC) developed the first PLC, General Motors auto assembly line in the United States on trial, was a success. This new type of industrial control equipment for its straightforward, easy operation, high reliability, universal and flexible, small size, long life and so on, to 1971, has been successfully applied to food, beverage, metallurgy, paper and other industrial . The emergence of new industrial control devices, but also by the rest of the world's attention. 1971, Japan imported from the United States this new technology, and soon developed a Japan's first PLC. In 1973, Western European countries have also developed their first PLC. China's development since 1974. In industrial applications since 1977.PLC DefinitionPLC's inception, although time is not long, but developing rapidly. In order to make the production and development of standardized, the United States National Electrical Manufacturers Association NEMA (National Electrical Manufactory Association) After four years of investigation, in 1984, officially named its first PC (ProgrammableController), and to the PC made the following definition: "PC is a digital electronic device, which uses a programmable memory store instructions. used to perform, such as logic, sequence, timing, counting and calculus and other functions, and digital or similar input / output module to control the various kinds of machinery or work procedures. a digital electronic computer if the function involved in the implementation of the PC, is regarded as PC, but does not include drum or similar mechanical sequence controller. "after the International Electrotechnical Commission (IEC) has promulgated of the PLC standard first draft, second draft, and in February 1987 it adopted a definition: "Programmable Logic Controller is a digital computing operation of an electronic system designed for applications in industrial environments designed for . It uses a class of programmable memory, for its internal storage procedures, the implementation of logical operations, sequential control, timing, counting and arithmetic operations such as user-oriented instructions, and, through digital or analog input / output control of all types of machinery or production processes. programmable logic controller and its related peripherals, will all be easy and industrial control systems into a single, easy-to expand its principle of functional design. "In short, the programmable controller is a computer, it is designed for industrial environment applications, design and manufacture of computers. It has a wealth of input / output interface, and has a strong drive capability. But the programmable controller products is not directed at a specific industrial application in practical applications, the hardware must be chosen according to the actual needs of configuration, the software must be designed according to the preparation of control requirements.PLC stage of developmentAlthough the PLC came not long, but with the emergence of microprocessors, large-scale, ultra-large scale integrated circuit technology, the rapid development and data communication technology continues to advance, PLC is also developing rapidly, its development process can be divided into roughly three phases:Early PLC (60 mid-late -70)Circuit has been improved to meet the requirements of industrial control field. Device device used mainly small and medium-scale discrete components and integrated circuits, memory with magnetic core memory. Were also taken some measures to improve its anti-jamming capability. Insoftware programming, using the majority of electrical engineers and technicians are familiar with relay control circuit of the way - ladder. Therefore, the early performance of PLC is superior to relay control device, its advantages, including simple and easy to understand, easy to install, small size, low energy consumption, there is trouble instigated can be reused. Which PLC-specific programming languages - Ladder has been in use ever since.The mid-PLC (70 in the mid -80 era, post-)In the 70's, the emergence of the microprocessor so that PLC has undergone tremendous changes. The United States, Japan, Germany and some manufacturers have began to use microprocessors as the PLC central processing unit (CPU). In this way, so that PLC may function greatly enhanced. The software side, in addition to maintaining its original logic operations, timing, counting and other functions, it also increased the arithmetic operations, data processing and transmission, communication, self-diagnostic functions. On the hardware side, in addition to maintaining their original switch module, it also increased the analog module, remote I / O Modules, all kinds of special function modules. And expanded memory capacity, so that the coil increase in the number of logic, it also provides a certain amount of data registers, so that PLC was able to expand the scope of application.Recent PLC (80 era, post-present)Into the 80s, the late, due to ultra-large scale integrated circuit technology, the rapid development of the microprocessor market prices have fallen considerably, making various types of PLC used in a general increase in the microprocessor when the times. Furthermore, in order to further improve the processing speed of PLC, the manufacturers have also developed a dedicated logic chip. This makes the PLC hardware and software functionality has undergone tremendous changes.Classification of PLCSmall PLCSmall PLC, I / O points generally below 128 points, which is characterized by small size, compact structure, the entire hardware integration, in addition to switching the amount of I / O, it also can be connected to analog I / O, and various other special functions module. It includes the implementation of logical operations, timing, counting, arithmetic operations, data processing and transmission, communications networking, and command a variety of applications.Medium-sized PLCMedium-sized PLC modular structure, its I / O points is generally between 256 ~ 1024 points. I / O approach In addition to the general common PLC outside the scanning approach, but also by direct approach, that is, scan the user program process, the direct read input, refresh the output. It joins a variety of special function modules,communication networking stronger, richer instruction set, memory, greater capacity, faster scanning speed.Large PLCGeneral I / O points at 1024 points or more known as a large PLC. Large-scale PLC software and hardware features strong, with strongself-diagnostic features. Strong communications networking capabilities, there are a variety of communications networking modules, can constitute a three communications networks to achieve factory production management automation. Large-scale PLC also can be used three CPU constitutes a voting-style system to make the machine more reliable.The basic structure of PLCPLC is essentially a specialized in industrial control computer, its hardware structure is basically the same as with the micro-computer, power supply, memory, I / O and timer alert status, and enables diagnosis of the user program syntax errors. When the PLC put into operation, the first way it scans the scene to receive the status of various input devices and data, and were deposited in I / O image area, and then one by one from the user program memory in the user program to read, after a command interpreter and press instruction logic or arithmetic implementation of the provisions of the results into the I / O image area or data registers. And all other users of program execution has finished, and finally I / O image area of all the output within the state or the output register data to the appropriate output device, and so on to run until stopped running. To further enhance the reliability of PLC in recent years, large PLC also constitute a redundant dual-CPU system, or the vote by three-CPU systems. In this way, even if a CPU failure, the entire system still running.MemoryMemory storage system software, known as the system program memory. Application software stored in memory as the user program memory.PLC memory types commonly used1. RAM (Random Assess Memory), which is a read / write memory (random access memory), its access to the fastest from the lithium battery.2. EPROM (Erasable Programmable Read Only Memory), which is a read-only memory can be erased. In the power cases, the entire contents of memory remain unchanged. (Continuous irradiation under UV-erasable memory content).3. EEPROM (Electrical Erasable Programmable Read Only Memory), which is a electrically erasable read-only memory. Using the programmer can be easily stored for its content be modified.PowerPLC's power throughout the system plays a very important role too. If you do not have a good, reliable power supply system may not work properly, so the PLC, the manufacturer of the power supply design andmanufacture of very great importance. General AC voltage fluctuation at +10% (+15%) range, and can not take other measures which will be directly connected to the AC power line PLC to go.PLC worksThe initial development and production of the PLC is mainly used to replace the traditional posed by the relay contactor control device, but the two operating mode is the same: Control unit run in parallel with the hard logic of the way, that is, if the relay coil power, or power outages, all of the contacts of the relay (including its normally open or normally closed contact) in the relay control circuit which will immediately place the same time, movements; PLC's CPU scan logic is applied in order to run user program way, that is, if an output coil or coils are connected or disconnected logic of the coil all the contacts (including its normally open or normally closed contact) is not an immediate action, must wait for the scan to the contact action only when the . In order to eliminate between runs in different ways due to differences caused by taking into account all kinds of contact relay control device operating time is generally more than 100ms, while the PLC user program scan time generally small 100ms, therefore, PLC used of a micro-computer is different from the normal operating mode --- scanning technology. So that for the I / O response-demanding situations, PLC and relay control device on the handling of the results there is no distinction between.ScanningInput sampling phase, the input sampling stage, PLC in order to scanning mode in turn to read all input states and data, and entered into the I / O image area in the corresponding unit too. After the input sample, transferred to the user program execution and output refresh period. In both phases, even if the input state and data changes, I / O image area in the state and the corresponding unit data will not change. Therefore, if the input is a pulse signal, then the pulse width must be greater than one scan cycle, in order to ensure that under any circumstances, this input can be read into.The user program implementation phase, the user program implementation phase, PLC is always a top-down in the order according to scan the user program (ladder diagram). A ladder for each scan when the scan is always the first ladder left of the control circuit formed by the contact, according to the first left and right, first on the order following the contacts formed by the control circuit logic operation , and then the results of logical operation, refresh the logic coils in the system RAM storage area in the state of the corresponding bit; or refresh the output coil in the I / O image area in the state of the corresponding bit; or determine whether to implement the ladder of the provisions of the special function instruction. That is, the user program execution, only the input point in the I / O mapping and data state of the regionwill not change, while the other output point and soft-devices in I / O image area or system RAM storage area status and data are likely to change, but also came in above the ladder, and the procedure implementation of the results would be ranked in the following any use of these coils or data ladder work; on the contrary, came in below the ladder, the be refreshed logic coil state or data can only be to the next row of a scan cycle in order to right the above procedures in their work.Output refresh periodWhen the scan after the end of user program, PLC enters the output refresh phase. In the meantime, CPU according to I / O image area corresponding to the state, and data refresh all of the output latch circuit, and then through the output circuit drives the appropriate peripherals. At this time, is the real output of PLC. Similarly, a number of ladder, its ranking is different from the results of the implementation is also different. In addition, the user program run using scanning results and relay control unit of the hard logic of the results of parallel runs differ. Of course, if the scan cycle time occupied for the entire operation can be ignored, then there is no difference between the two had. In general, PLC scan cycle, including self-diagnostics, communications and so on, as shown below, that is, a scan cycle is equal to self-diagnosis, communication, input sampling, user program execution, the output refresh so the sum of all time.PLC's I / O response timeIn order to enhance PLC, anti-jamming capability, improve its reliability, PLC input terminal of each switch have adopted technologies such as optical isolation. In order to achieve the relay control circuit of the hard logic of parallel control, PLC using micro-computer is different from the normal operating mode (scanning technology). These two main reasons for making PLC have I / O response than the general industrial microcomputer control system composed of more than full, its response time at least equal to one scan cycle, generally more than one scan cycle, or even longer. The so-called I / O response time refers to a particular input signals from the PLC changes to the system began to change in the output signal the time required.PLC's I / O System 360毕业设计网 I / O addressing modePLC hardware architecture mainly consists of two kinds of modular and modular. The former will be a major part of the PLC (including the I / O systems and power supplies, etc.) all installed in one chassis. The latter will be the major PLC hardware modules are made separately, and then by the user according to the selected module needs to be inserted on the slot PLC rack to form a PLC system. No matter what sort of hardware architecture, are used to connect industrial field must be established in various input / output point and the PLC, I / O correspondence betweenthe image area, that is to each input / output point to a clear set of addresses This correlation was used approach is called I / O addressing mode.I / O addressing methods are available as follows:Fixed I / O addressing modeThis I / O addressing mode by the PLC manufacturer in the design, production and PLC determined at the time, and each of its input / output point has a clear fixed address. In general, modular PLC using this I / O addressing mode.Switch setting I / O addressing modesThis I / O addressing mode by the user through the switch on the chassis and module configuration to determine the location of the.Software to set the I / O addressing modeThis I / O addressing mode is a user through the software to the preparation of I / O address assignment table to determined.译文PLC的基本概念可编程控制器(Programmable Controller)是计算机家族中的一员，是为工业控制应用而设计制造的。

可编程逻辑控制器〔PLC 〕1．PLC介绍众所周知，科技世界里只有一个永恒真理，那就是变化。

这在可编程逻辑控制器〔PLC〕及其各种应用的开展过程中尤为明显。

自从三十多年前将PLC引进以来，PLC 已经在广泛的工业领域中成为几十万控制系统的根底。

从本质上讲，PLC是一种用高度专业化语言编程的工业计算机，并继续受益于计算机和信息技术领域的技术进步，它的最突出之处是小型化和通信功能。

可编程逻辑控制器I/O通道规那么包括所有的输入触点和输出触点，扩展能力和最大数量的通道。

触点数量是输入点和输出点的总和。

PLC可以指定这些值的任何可能的组合。

扩展单元可以被堆栈或互相连接来增加总的控制能力。

最大数量的通道是在一个扩展系统中输入和输出通道的最大总数量。

PLC系统规那么包括扫描时间，指令数量，数据存储和程序存储。

扫描时间是 PLC需要的用来检测输入输出模块的时间。

指令是用于PLC软件〔例如数学运算〕的标准操作。

数据存储是存储数据的能力。

程序存储是控制软件的能力。

用于可编程逻辑控制器的输入设备包括DC，AC，中间继电器，热电偶，RTD，频率或脉冲，晶体管和中断信号输入；输出设备包括DC，AC，继电器，中间继电器，频率或脉冲，晶体管，三端双向可控硅开关元件；PLC的编程设备包括控制面板，手柄和计算机。

可编程逻辑控制器用各种软件编程语言来控制。

这些语言包括IEC61131-3，顺序执行表〔SFC〕，动作方块图〔FBD〕，梯形图〔LD〕，结构文本〔ST〕，指令序列〔IL〕，继电器梯形图〔RIL〕，流程图，C语言和Basic语言。

IEC61131-3编程环境能支持五种语言，用国际标准加以标准，分别为SFC，FBD，LD，ST和IL。

这便允许了多卖主兼容性和多种语言编程。

SFC是一种图表语言，它提供了编程顺序的配合，就能支持顺序选择和并列选择，二者择其一即可。

FBD用一种大的运行库，以图表形式建立了一些复杂的过程。

标准数学和逻辑运行可以与用户交流和接口运行相结合。

Programmable Logic Controllers (PLCs) 1 .About Programmable Logic Controllers (PLCs)PLCs (programmable logic controllers) are the control hubs for a wide variety of automated systems and processes. They contain multiple inputs and outputs that use transistors and other circuitry to simulate switches and relays to control equipment. They are programmable via software interfaced via standard computer interfaces and proprietary languages and network options.Programmable logic controllers I/O channel specifications include total number of points, number of inputs and outputs, ability to expand, and maximum number of channels. Number of points is the sum of the inputs and the outputs. PLCs may be specified by any possible combination of these values. Expandable units may be stacked or linked together to increase total control capacity. Maximum number of channels refers to the maximum total number of input and output channels in an expanded system. PLC system specifications to consider include scan time, number of instructions, data memory, and program memory. Scan time is the time required by the PLC to check the states of its inputs andoutputs. Instructions are standard operations (such as math functions) available to PLC software. Data memory is the capacity for data storage. Program memory is the capacity for control software.Available inputs for programmable logic controllers include DC, AC, analog, thermocouple, RTD, frequency or pulse, transistor, and interrupt inputs. Outputs for PLCs include DC, AC, relay, analog, frequency or pulse, transistor, and triac. Programming options for PLCs include front panel, hand held, and computer.Programmable logic controllers use a variety of software programming languages for control. These include IEC 61131-3, sequential function chart (SFC), function block diagram (FBD), ladder diagram (LD), structured text (ST), instruction list (IL), relay ladder logic (RLL), flow chart, C, and Basic. The IEC 61131-3 programming environmentprovides support for five languages specified by the global standard: Sequential Function Chart, Function Block Diagram, Ladder Diagram, Structured Text, and Instruction List. This allows for multi-vendor compatibility and multi-language programming. SFC is a graphical language that provides coordination of program sequences, supporting alternative sequence selections and parallel sequences. FBD uses a broad function library to build complex procedures in a graphical format. Standard math and logic functions may be coordinated with customizable communication and interface functions. LD is a graphic language for discrete control and interlocking logic. It is completely compatible with FBD for discrete function control. ST is a text language used for complex mathematical procedures and calculations less well suited to graphical languages. IL is a low-level language similar to assemblycode. It is used in relatively simple logic instructions. Relay Ladder Logic (RLL), or ladder diagrams, is the primary programming language for programmable logic controllers (PLCs). Ladder logic programming is a graphical representation of the program designed to look like relay logic. Flow Chart is a graphical language that describes sequential operations in a controller sequence or application. It is used to build modular, reusable function libraries. C is a high level programming language suited to handle the most complex computation, sequential, and data logging tasks. It is typically developed and debugged on a PC. BASIC is a high level language used to handle mathematical, sequential, data capturing and interface functions.Programmable logic controllers can also be specified with a number of computer interface options, network specifications and features. PLC power options, mounting options and environmental operating conditions are all also important to consider.2 .INTRODUCTIONFor simple programming the relay model of the PLC is sufficient. As more complex functions are used the more complex VonNeuman model of the PLC must be used. A VonNeuman computer processes one instruction at a time. Most computers operate this way, although they appear to be doing many things at once.Input is obtained from the keyboard and mouse, output is sent to the screen, and the disk and memory are used for both input and output for storage. It travels through buffering circuits before it enters the CPU. The CPU outputs data through other circuits. Memory and disks are used for storage of data that is not destined for output. If we look at a personal computer as a controller, it is controlling the user by outputting stimuli on the screen, and inputting responses from the mouse and the keyboard.A PLC is also a computer controlling a process. When fully integrated into an application the analogies become;inputs - the keyboard is analogous to a proximity switchinput -circuits - the serial input chip is like a 24Vdc input card computer - the 686 CPU is like a PLC CPU unitoutput - circuits - a graphics card is like a triac output cardoutputs - a monitor is like a lightstorage - memory in PLCs is similar to memories in personal computersIt is also possible to implement a PLC using a normal Personal Computer, although this is not advisable. In the case of a PLC the inputs and outputs are designed to be more reliable and rugged for harsh production environments.3 .OPERATION SEQUENCEAll PLCs have four basic stages of operations that are repeated many times per second. Initially when turned on the first time it will check it’s own hardware and software for faults. If there are no problems it will copy all the input and copy their values into memory, this is called the input scan. Using only the memory copy of the inputs the ladder logic program will be solved once, this is called the logic scan. While solving the ladder logic the output values are only changed in temporary memory. When the ladder scan is done the outputs will be updated using the temporary values in memory, this is called the output scan. The PLC now restarts the process by starting a self check for faults.The input and output scans often confuse the beginner, but they are important. The input scan takes a snapshot of the inputs, and solves thelogic. This prevents potential problems that might occur if an input that is used in multiple places in the ladder logic program changed while half way through a ladder scan. Thus changing the behaviors of half of the ladder logic program. This problem could have severe effects on complex programs that are developed later in the book. One side effect of the input scan is that if a change in input is too short in duration, it might fall between input scans and be missed.When the PLC is initially turned on the normal outputs will be turned off. This does not affect the values of the inputs.3 .1 The Input and Output ScansWhen the inputs to the PLC are scanned the physical input values are copied into memory. When the outputs to a PLC are scanned they are copied from memory to the physical outputs. When the ladder logic is scanned it uses the values in memory, not the actual input or output values. The primary reason for doing this is so that if a program uses an input value in multiple places, a change in the input value will not invalidate the logic. Also, if output bits were changed as each bit was changed, instead of all at once at the end of the scan the PLC would operate much slower.3 .2 The Logic ScanLadder logic programs are modelled after relay logic. In relay logic each element in the ladder will switch as quickly as possible. But in a program elements can only be examines one at a time in a fixed sequence. Consider the ladder logic in Figure 4, the ladder logic will be interpreted left-to-right, top-to-bottom. In the figure the ladder logic scan begins at the top rung. At the end of the rung it interprets the top output first, then the output branched below it. On the second rung it solves branches, before moving along the ladder logic rung.The logic scan sequence become important when solving ladder logic programs which use outputs as inputs. It also becomes important when considering output usage. Consider Figure 5, the first line of ladder logic will examine input A and set output X to have the same value. The second line will examine input B and set the output X to have the opposite value. So the value of X was only equal to A until the second line of ladder logic was scanned. Recall that during the logic scan the outputs are onlychanged in memory, the actual outputs are only updated when the ladder logic scan is complete. Therefore the output scan would update the real outputs based upon the second line of ladder logic, and the first line of ladder logic would be ineffective.4 . PLC STATUSThe lack of keyboard, and other input-output devices is very noticeable on a PLC. On the front of the PLC there are normally limited status lights. Common lights indicate;power on - this will be on whenever the PLC has powerprogram running - this will often indicate if a program is running, or if no program is runningfault - this will indicate when the PLC has experienced a major hardware or software problemThese lights are normally used for debugging. Limited buttons will also be provided for PLC hardware. The most common will be a run/program switch that will be switched to program when maintenance is being conducted, and back to run when in production. This switch normally requires a key to keep unauthorized personnel from altering the PLC program or stopping execution. A PLC will almost never have an on-off switch or reset button on the front. This needs to be designed into the remainder of the system.The status of the PLC can be detected by ladder logic also. It is common for programs to check to see if they are being executed for the first time, as shown in Figure 6. The ’first scan’ input will be true on the very first time the ladder logic is scanned, but false on every other scan. In this case the address for ’first scan’ in a PLC-5 is ’S2:1/14’. With the logic in the example the first scan will seal on ’light’, until ’clear’ is turned on. So the light will turn on after the PLC has been turned on, but it will turn off and stay off after ’clear’ is turned on. The ’first scan’ bit is also referred to at the ’first pass’ bit.5 . MEMORY TYPESThere are a few basic types of computer memory that are in use today.RAM (Random Access Memory) - this memory is fast, but it will lose its contents when power is lost, this is known as volatilememory. Every PLC uses this memory for the central CPU whenrunning the PLC.ROM (Read Only Memory) - this memory is permanent and cannot be erased. It is often used for storing the operating system forthe PLC.EPROM (Erasable Programmable Read Only Memory) - this is memory that can be programmed to behave like ROM, but it can be erasedwith ultraviolet light and reprogrammed.EEPROM (Electronically Erasable Programmable Read Only Memory) –This memory can store programs like ROM. It can be programmedand erased using a voltage, so it is becoming more popular thanEPROMs.All PLCs use RAM for the CPU and ROM to store the basic operating system for the PLC. When the power is on the contents of the RAM will be kept, but the issue is what happens when power to the memory is lost. Originally PLC vendors used RAM with a battery so that the memory contents would not be lost if the power was lost. This method is still in use, but is losing favor. EPROMs have also been a popular choice for programming PLCs. The EPROM is programmed out of the PLC, and then placed in the PLC. When the PLC is turned on the ladder logic program on the EPROM is loaded into the PLC and run. This method can be very reliable, but the erasing and programming technique can be time consuming. EEPROM memories are a permanent part of the PLC, and programs can be stored in them like EPROM. Memory costs continue to drop, and newer types (such as flash memory) are becoming available, and these changes will continue to impact PLCs.6 . SOFTWARE BASED PLCSThe dropping cost of personal computers is increasing their use in control, including the replacement of PLCs. Software is installed that allows the personal computer to solve ladder logic, read inputs from sensors and update outputs to actuators. These are important to mention here because they don’t obey the previous timing model. For example,if the computer is running a game it may slow or halt the computer. This issue and others are currently being investigated and good solutions should beexpected soon.7 . SUMMARY• A PLC and computer are similar with inputs, outputs, memory, etc.• The PLC continuously goes through a cycle including a sanity check, input scan, logic scan, and output scan.• While the logic is being scanned, changes in the inputs are not detected, and the outputs are not updated.• PLCs use RAM, and sometime EPROMs are used for permanent programs.中文翻译1．PLC介绍PLCS（可编程逻辑控制器）是用于各种自动控制系统和过程的可控网络集线器。

plc英语词汇对照表PLC相关词汇发音词性释义。

PLC[ˌpiː el ˈsiː]n.（名词）可编程逻辑控制器（Programmable Logic Controller）Input[ˈɪnpʊt]n.（名词）/v.（动词）输入；投入；把…输入计算机。

Output[ˈaʊtpʊt]n.（名词）/v.（动词）输出；产量；输出端；输出量；输出数据；（将数据）输出。

Relay[ˈriːleɪ]n.（名词）/v.（动词）继电器；接替人员，轮换者；传递；转播；转接（电话）；转播（电视或广播讯号）Sensor[ˈsensə(r)]n.（名词）传感器；敏感元件；探测设备。

Actuator[ˈæktʃueɪtə(r)]n.（名词）执行器；促动器；作动器；激励器。

Logic[ˈlɒdʒɪk]n.（名词）逻辑；逻辑学；逻辑性；推理方法；逻辑系统。

Programming[ˈprəʊɡræmɪŋ]n.（名词）编程；程序设计；（节目）编排，选编。

Instruction[ɪnˈstrʌkʃn]n.（名词）指令；指示；教导；用法说明；操作指南。

Address[əˈdres]n.（名词）/v.（动词）地址；演说；称呼；处理（问题）；向…说话；称呼（某人）；写明收件人姓名地址。

Data[ˈdeɪtə]n.（名词）数据；资料；材料（datum的复数）Bit[bɪt]n.（名词）位；比特（二进制信息单位）Byte[baɪt]n.（名词）字节；位组；8个比特。

Register[ˈredʒɪstə(r)]n.（名词）/v.（动词）寄存器；登记；注册；记录；挂号邮寄；正式提出（投诉等）Latch[lætʃ]n.（名词）/v.（动词）门闩；插销；碰锁；弹簧锁；锁住；闩上；抓住；占有。

Counter[ˈkaʊntə(r)]n.（名词）/v.（动词）计数器；柜台；（对意见、态度等的）反对；反驳；抵制；（拳击或摔跤比赛中的）击打，反击；计算；计数；（尤指按顺序）数数。