三江学院
毕业设计(论文)外文资料翻译
院系高职院
专业电气工程及其自动化
学生姓名谌忠兴
班级学号B125071005
外文出处https://www.doczj.com/doc/fb12508454.html,/view/9b794f6c25c52cc
58bd6be0f.html
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Programmable logic controller
A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of e lectromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtur es. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multipl e inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and esistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PL C is an example of a real time system since output results must be produced in response to input conditions within a bo unded time, otherwise unintended operation will result.
1.History
The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmabl e logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed.
Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The pro cess for pdating such facilities for the yearly model change-over was very time consuming and expensive, as electrician s needed to individually rewire each and every relay.
In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacemet for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedfor d, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the r esult. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this ne w product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley,who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronic s, and later acquired by German Company AEG and then by French Schneider Electric, the current owner.
One of the vey first 084 models built is now on display at Modicon's headquarters in North Andover, Massacet. It was presented to Modicon by GM,when the unit was retired after nearly twenty years of unintrrupted service. Modicon used the 84 moniker at the end of its product range until the 984made its appearance. The automotive industry is still o ne of the largest users of PLCs.
2.Development
Early PLCs were designed to replace relay logic systems. These PLCs were programmed in "ladder logic", which strongly resembles a schematic diagram of relay logic. This program notation was chosen to reduce training demands for the existing technicians. Other early PLCs used a form of instruction list programming, based on a stack-based logi c solver.
Modern PLCs can be programmed in a variety ofways, from ladder logic to more traditional programming langua ges such as BASIC and C. Another method is State Logic, a very high-level programming language designed to progra m PLCs based on state transition diagrams.
Many early PLCs did not have accompanying programming terminals that were capable of graphical representati on of the logic, and so the logic was instead represented as a series of logic expressions in some version of Boolean fo rmat, similar to Boolean algebra. As programming terminals evolved, it became more common for ladder logic to be u sed, for the aforementioned reasons. Newer formats such as State Logic and Function Block (which is similar to the w ay logic is depicted when using digital integrated logic circuits) exist, but they are still not as popular as ladder logic.
A primary reason for this is that PLCs solve the logic in a predictable and repeating sequence, and ladder logic allows the programmer (the person writing the logic) to see any issues with the timing of the logic sequence more easily than would be possible in other formats.
2.1Programming
Early PLCs, up to the mid-1980s, were programmed using proprietary programming panels or special-purpose pr ogramming terminals, which often had dedicated function keys representing the various logical elemnts of PLC progra ms. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were very minimal due to lack of memory capacity. The very oldest PLCs used non-volatile magnetic core memory.
More recently, PLCs are programmed using application software on personal computers. The computer is connec ted to the PLC through Ethernet, RS-232, RS-485 or RS-422 cablig. The programming software allows entry and editi ng of the 3 ladder-style logic. Generally the software provides functions for debugging and troubleshooting the PLC s oftware, for example, by highlighting portions of the logic to show current status during operation or via simulation. T he software willupload and download the PLC program, for backup and restoration purposes. In some models of progr ammable controller, the program is transferred from a personal computer to the PLC though a programming board whi ch writes the program into a removable chip such as an EEPROM or EPROM.
3.Functionality
The functionality of the PLC has evolved over the years to include sequential relay control, motion control, proces s control, distributed control systems and networking. The data handling, storage, processing power and communicatio n capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combi ned with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications . Regarding the practicality of these desktop computer based logic controllers, it is important to note that they have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperat ure, humidity, vibration, and longevity as the processors used in PLCs. In addition to the hardware limitations of deskto p based logic, operating systems such as Windows do not lend themselves to deterministic logic execution, with the res ult that the logic may not always respond to changes in logic state or input status with the extreme consistency in timin g as is expected from PLCs. Still, such desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs.
In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have be come more common and accepted. These are very much like PLCs, and are used in light industry where only a few poi nts of I/O (i.e. a few signals coming in from the real world and a few going out) are involved, and low cost is desired. T hese small devices are typically made in a common physical size and shape by several manufacturers, and branded by t he makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have between 8 and 12 digital inputs, 4 and 8 digital ou tputs, and up to 2 analog inputs. Size is usually about 4" wide, 3" high, and 3" deep. Most such devices include a tiny p ostage stamp sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visi ble at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-butto
n plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and e dit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button se t for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modu lar or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic.
4.PLC Topics
4.1.Features
The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and a ctuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of co mplex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a s imple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC. 4.2Syst em scale
A small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O. Modular PLCs have a chassis (also called a rack) into which are place d modules with different functions. The processor and selection of I/O modules is customised for the particular applicat ion. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special h igh speed serial I/O link is used so that racks can be distributed away from the processor, reducing the wiring costs for l arge plants.
4.3User interface
PLCs may need to interact with people for the purpose of configuration, alarm reporting or everyday control
A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphic al touch screens. More complex systems use a programming and monitoring software installed on a computer, with the PLC connected via a communication interface. 4.4Communications
PLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or Ethernet. Modbus, BA Cnet or DF1 is usually included as one of the communications protocols. Other options include various fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protoc ols
Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser.
PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows sep arate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the com munication link. These communication links are also often used for HMI devices such as keypads or PC-type workstati ons.
4.5Programming
PLC programs are typically written in a special application on a personal computer, then downloaded by a direct-c onnection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or s ome other non-volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays.
Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. A gra
phical programming notation called Sequential Function Charts is available on certain programmable controllers. Initia lly most PLCs utilized Ladder Logic Diagram Programming, a model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today.
IEC 61131-3 currently defines five programming languages for programmable control systems: FBD (Function block diagram), LD (Ladder diagram), ST6 (Structured text, similar to the Pascal programming language), IL (Instruct ion list, similar to assembly language) and SFC (Sequential function chart). These techniques emphasize logical organi zation of operations.
While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addres sing, memory organization and instruction sets mean that PLC programs are never perfectly interchangeable between d ifferent makers. Even within the same product line of a single manufacturer, different models may not be directly comp atible.
5.PLC compared with other control systems
PLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing w here the cost of developing and maintaining the automation system is high relative to the total cost of the automation, a nd where changes to the system would be expected during its operational life. PLCs contain input and output devices c ompatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers o n expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the ca se of mass-produced goods, customized control systems are economic due to the lower cost of the components, which c an be optimally chosen instead of a "generic" solution, and where the non-recurring engineering charges are spread ove r thousands or millions of units.
For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer di shwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.
A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and s o the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an ex ample; millions of units are built each year, and very few end-users alter the programming of these controllers. Howeve r, some specialty vehicles such as transit busses economically use PLCs instead of custom-designed controls, because t he volumes are low and the development cost would be uneconomic.
Very complex process control, such as used in the chemical industry, may require algorithms and performance be yond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customize d solutions; for example, aircraft flight controls.
Programmable controllers are widely used in motion control, positioning control and torque control. Some manufa cturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements.
PLCs may include logic for single-variable feedback analog control loop, a "proportional, integral, derivative" or " PID controller". A PID loop could be used to control the temperature of a manufacturing process, for example. Historic ally PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousan ds of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boun dary between DCS and PLC applications has become less distinct.
PLCs have similar functionality as Remote Terminal Units. An RTU, however, usually does not support control al gorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs and DCSs are increa
singly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PL Cs, although nearly all vendors also offer proprietary alternatives and associated development environments.
6.Digital and analog signals
Digital or discrete signals behave as binary switches, yielding simply an On or Off signal (1 or 0, True or False, re spectively). Push buttons, limit switches, and photoelectric sensors are examples of devices providing a discrete signal. Discrete signals are sent using either voltage or current, where a specific range is designated as On and another as Off. For example, a PLC might use 24 V DC I/O, with values above 22 V DC representing On, values below 2VDC represe nting Off, and intermediate values undefined. Initially, PLCs had only discrete I/O.
Analog signals are like volume controls, with a range of values between zero and full-scale. These are typically int erpreted as integer values (counts) by the PLC, with various ranges of accuracy depending on the device and the numbe r of bits available to store the data. As PLCs typically use 16-bit signed binary processors, the integer values are limited between -32,768 and +32,767. Pressure, temperature, flow, and8 weight are often represented by analog signals. Anal og signals can use voltage or current with a magnitude proportional to the value of the process signal. For example, an analog 0 - 10 V input or 4-20 mA would be converted into an integer value of 0 - 32767.
译文：
可编程逻辑控制器
可编程逻辑控制器（PLC）或可编程序控制器是用于机电过程自动化的数字计算机，例如控制机械厂生产线、游乐设施或照明装置。可编程控制器在许多工业和机器中使用。与通用的计算机不同的是，PLC是专为多个输入和输出管理，扩展温度范围、不受电磁噪音影响、抗震动和冲击所设计。控制器的操作程序通常存储在电池供电或非易失性的内存中。PLC是实时的系统，因为系统产生的输出结果必须在有限的时间内回馈到输入，否则会导致错误操作。 1.历史 PLC发明是针对于美国汽车制造行业的需要。可编程逻辑控制器最初通过了在软件版本更换硬连线的控制板生产模式更改时的汽车工业。在PLC之前，控制、程序化和安全联锁逻辑制造汽车是使用上百或上千的继电器、凸轮计时器、鼓定序仪和专用的闭环控制器来完成的。在每年更新模型等设施转变过程是非常耗时并且成本高昂的，这是因为电工需要单独地再接电线给每个中转。在1968
年 GM Hydramatic（自动输电分局）发布通用汽车公司的提议，电子替代布线中继系统。获奖的提案来自贝得福得，马萨诸塞的贝得福得同事。第一个PLC选定084，因为它是贝得福得同事的第八十四个项目。贝得福得同事建立了一家新的公司致力开发、生产、销售，和服务这一新产品：Modicon，代表模块化数字控制器。迪克·莫利，被认为是PLC之父，他是从事该项目的人之一。1977年古尔德电子公司当前所有者收购法国施耐德电气公司同德国公司AEG并售予该品牌为Modicon。
084模型之一首次被设在北部安多弗的Modicon总部马萨诸塞州。这是专门9 为通用汽车服务的，并且经过了近二十多年的不间断服务。直至984出现，Modicon使用的84名字才在其产品范围中结束。
汽车工业仍是PLC的最大用户之一。汽车工业仍是PLC的最大用户之一。
2.发展
早期的可编程控制器是设计来取代继电器逻辑系统。这些可编程控制器的“阶梯逻辑”是与继电器逻辑示意图非常类似的。选择此程序表示法的目的是为了减少对现有技术人员的培训需求。其他早期的可编程控制器使用指令列表编程，基于一个堆栈编程逻辑求解器进行求解。
现代可编程控制器在各种各样的方式可以被编程，从梯形逻辑语言到更加传统的编程语言例如BASIC和C语言。另一个方法是状态逻辑，被设计的一种非常高级编程语言根据状态转换图的可编程控制器编程。
很多早期可编程控制器没有可编程终端的逻辑图形表示法，逻辑反而是被描绘成一系列在一些版本的布尔格
式的逻辑表达式，类似于布尔代数。随着编程码发展，由于上述原因它变成更常见的梯形逻辑语言。更新的格式如国家逻辑和功能块（这是类似的逻辑描述使用数字逻辑集成电路时的方式）的存在，但它们仍没有梯形逻辑语言流行。一个主要原因是可编程控制器解决问题用一个可预测和重复的序列的逻辑，并且梯形逻辑语言可以用其他格式让程序员（写逻辑）的人看到逻辑的时间，所有问题更加容易地程序化。
2.1编程
早期的PLC，到80年代中期，都是用专有的编程版或专用编程终端，往往有专门的功能键，代表各种PLC程序逻辑元件。程序存储在盒式磁带盒上。由于缺少的内存容量很少用于打印设备。最古老的可编程控制器使用的是非易失性磁核心内存。
最期PLC在个人计算机上使用应用软件编程。计算机连接到PLC通过以太网RS-232,RS-485或RS-422缆线连接。编程软件允许输入梯式逻辑编程。通常，软件提供了用于调试和故障排除的功能，例如在操作过程中或通过仿真的逻辑部分PLC软件突出显示当前状态。该软件将上传和下载PLC程序以便备份和恢复。在某些型号的PLC中虽然程序写入一个可移动的芯片，如EEPROM或EPROM，但该方案还是得从个人电脑传输到PLC 编程版。
3.功能
PLC的功能经过多年的发展，包括连续的继电器控制，运动控制，过程控制，分布式控制系统和网络。一些现代PLC的数据处理，存储，处理能力和通信能力相当于台式电脑。PLC编程结合远程I/O硬件，一台通用台式计算机允许在某些应用中重叠使用某一可编程控制器。在重工业中PLC被认为没有这些桌面计算机为主的逻辑控制器的实际性强，因为PLC在台式计算机系统中运行不是很稳定，并且，因为台式计算机硬件没有被设计成耐温度、湿气、振动和耐用作为可编程控制器的处理器。除桌面基于逻辑的硬件局限之外，例如Windows操作系统不适合自己的确定性逻辑的执行，结果是PLC逻辑不可能总是对规定逻辑变化的输入状态与极端性预计的时间一致。尽管如此，这样桌面逻辑被应用在较不重要情况，像实验室自动化和小型设施中使用该应用程序的要求不高，因为他们的价格一般都远远低于昂贵的PLC。
在最近数年，小产品称为PLR（可编程逻辑继电器），并且因为名字相似，变得更常见并被接受。这些很像PLC 已经应用于轻工业，它只有少部分的输入/输出（例如一些真实的输入输出信号）参与，低成本，很理想。这些小设备尺寸和形状比较普通地几位制造商制作，并且由更大的PLC制作商来填满他们低端产品规格。俗名包括PICO控制器、纳米PLC和其他的小控制器。多数这些控制器有在8到12数字输入、4到8数字输出，多达2个模拟输入。尺寸通常是4英寸宽、3英寸高、3英寸深。大多数这样的设备有一个小邮票大小的液晶屏幕来
观看简化梯子逻辑的输入/输出点（只有一小部分程序被可见于给定的时间）和状况，并且这些屏幕由一个电磁四通摇臂按钮操纵加上四个不同的用于浏览和编辑的逻辑电钮，类似于录像机遥控按钮。控制器大多数有一个小插座为通过连接RS-232或RS-485到个人计算机，以便程序员可能为编程使用简单的窗口应用而不是被迫使用微小的LCD和电钮。不像普通PLC，通常是模块化，大大扩展,控制器通常不会取模块化并且不是可扩展的，但是他们提供稳健设计的确定性和执行逻辑的价值比PLC少。
4.可编程序控制器PLC
4.1未来发展
从其他计算机来看，主要区别是可编程控制器具有特殊条件（例如，灰尘、湿、热、冷）和具有广泛的输入/输出（I/O）安排的设施。这些是连接PLC的传感器和执行器。可编程控制器是读取限制开关、模拟过程变量（如温度和压力）以及位置复杂的定位系统。有些人利用机器系统来查看光源与照明。执行器使可编程控制器操作电子电机、气动或液压缸、磁继电器、电磁线圈的模拟输出。输入/输出的安排可以建立一个简单的可编程控制器、或可编程序控制器可以用外部的I/O模块连接插入的计算机网络。
4.2系统规模
一个小的PLC是固定数量的输入和输出生成的连接。如果基础模型具有足够的I/O通常可扩展。
模块化可编程控制器有一个机箱（也称为机架）在其中放置具有不同的功能模块。处理器和I/O模块的选择被定制为特定的应用程序。几个机架可以有一个单个的处理器，可能会有成千上万的输入和输出。一种特殊的高速串行I/O环节是机架减少多个线路使用分布式离散处理器。
4.3使用界面
可编程控制器的配置、报警报告或日常控件可能需要与人进行交互。一个简单的系统可能使用按钮和指示灯与用户进行交互。可以用图形触摸屏文本显示。更复杂的系统使用PLC通过通信接口连接到一台计算机上安装的编程和监测软件来使用。
4.4通信
可编程控制器被建于通常的9针RS-232，也可以选择485或以太网的通信端口由环境影响评估。协议、BACnet或东方是通常作为通信协议之一包含其中。其它选项包括各项如构架或现场总线。在自动化协议的列表中列出了其他可能使用的通信协议。
最现代的可编程控制器可以通过一个网络，以一些其它的系统（例如，运行监控、监测控制与数据采集系统）或网络浏览器的计算机进行通信。
可编程控制器在较大的I/O系统中使用可能会有处理器之间的对等，这允许独立的部分是一个复杂的过程,同时让独立的控制子系统的沟通联系协调。这些通信链接也经常用于人机界面设备（例如键盘或PC型工作站）。
4.5编程
PLC程序通常是个人的计算机上写入一个特殊的应用程序，然后通过连接电缆或以上PLC网络直接下载。该程序存储在PLC备用电池内存或一些其他非易失性闪存中。通常，一个单一的PLC可以进行编程，以替换数以千计的继电器。
根据IEC61131-3的标准可以使用基于标准的编程语言编程PLC。可在某些可编程控制器上调用顺序功能图图形编程表示法。最初大多数可编程控制器利用阶梯逻辑图的模式，模拟机电控制面板设备（如继电器与线圈的联系）。此模型今天仍然是常见的。
IEC61131-3当前定义的可编程控制系统的五个编程语言：FBD（功能块图）LD（梯形图）、ST（结构化文本，类似于帕斯卡尔的编程语言）、IL（教学列表，类似于汇编语言）和SFC（顺序功能图）。这些技术强调逻辑组织的行动。
虽然PLC编程的基本概念是共同所有的生产商，I/O处理、内存组织和指令集不同设置PLC程序意味着不会不完全的可互换。即使在同一个单一的制造商产品线内不同的模型可能不直接兼容。
5.PLC相比其它控制系统
可编程控制器是可适应一系列自动化任务。这些都是自动化的在制造中通常工业过程开发和维护自动化系统的成本在哪里高，相对于总成本和其寿命期间预计将对系统更改。可编程控制器包含输入和输出设备兼容工业试验设备和管制，小电气的设计问题对预期操作是必要的。PLC应用程序通常是高度定制系统，因此成本包装可编程序控制器（PLC）的费用比一个具体定制设计的小控制器要高。另外一方面在批量生产货物的情况下自定义的控制系统是组成、成本较低的最佳选择，而不是一个非反复出现工程费用“普通”的解决方案。
不同的技术方法有大量的并且很简单的固定自动化任务。例如消费者用的洗碗机的机电凸轮计时器生产数量成本只有几美元。
一种基于微控制器的设计是需要成百上千个单位（设计电源供应器，输入/输出硬件和必要的检测和认证）和开发成本可以分散到很多的销售，最终用户不需要更改该控件。汽车应用程序就是一个例子：数以百万计的内置单位每一年需要建造，很少最终用户更改这些控制器的编程。然而，一些其他车辆如交通公共汽车经常定制设计的控制,而不是用PLC，因为数量很低,发展成本会赚不到钱的。
像使用在化工中的过程控件就非常复杂，可能需要算法和甚至超出高性能可编程控制器。非常高速的能力范围的性能或精度控件也可能需要自定义的解决方案，例如飞机飞行的控件。
可编程序控制器广泛用于运动控制、定位控制和转矩控制。一些制造商生产运动控制单元与PLC集成、G-code （涉及数控机床）可以用于指导机器运作。
可编程控制器可能包括一个“比例，积分，微分”的单变量反馈模拟控制循环的逻辑或“控制器”。以PID 回路可用于控制温度为例。历史上PLC通常配置只有少数模拟控制回路，通常配置可编程控制器将使用分布式的控制系统（DCS）的过程成百上千的循环。可编程控制器功能已经很强大了，可编程序控制器（PLC）与集散控制系统之间的边界应用已经不是很明显了。
可编程控制器具有类似于远程终端设备的功能。RTU，然而通常不支持或控制回路的控制算法。随着硬件迅速变得更强大和更便宜，RTU、PLC和DCS正在越来越多地开始有重叠，职责，并与PLC卖许多供应商的特点类似，RTU反之亦然。业界基于IEC61131-3创建程序上运行的RTU和PLC功能块语言规范，尽管几乎所有供应商还提供专有的替代方案及相关的开发环境。
6.数字和模拟信号
数字或离散信号就像二进制开关，创造出一个简单的开或关信号（分别为1或0，真或假）。按钮、限制的交换机和光电传感器都是提供一个离散的信号的设备。离散信号发送使用电压或电流，在特定的范围，对指定，另一个为关闭。例如PLC可能24V直流I/O，使用值为以上22DC 代表上，2VDC下面的值表示关闭，和中间值未定义。最初，可编程控制器只有离散的I/O。
模拟信号就像音量控制范围从0开始。这些通常被解释为整数值（计数），PLC与各种范围的精度取决于设备和用于存储数据的位数。可编程控制器通常使用16位二进制符号的处理器，范围-32768和32767之间的整数值。通常由模拟信号表示压力、温度、流量和重量。模拟信号可以使用大小成比例电压或电流过程信号的值。例如一个模拟0-10V或4-20mA的输入将转换为一个整数值0-32767。
非洲生物工程卷。7（15），第2621至2629年2008年8月4https://www.doczj.com/doc/fb12508454.html,/AJB ISSN 1684-5315 2008学术期刊约旦污水处理厂处理性能及水回用的适宜性 无论是在城市还是农村环境，水资源的更有效地利用都有一个增长的趋势。在约旦，水的需求增加，水资源短缺，导致人们对废水回用产生了兴趣。在这项工作中，分别测定四个废水处理厂的水质特点，并对废水特性进行了评估。在选定的污水处理厂中测量其进出水水质的生化需氧量，化学需氧量，总悬浮固体，总溶解固体，氨氮，和溶解氧。经过处理后的出水水质与约旦的标准进行了比较。结果表明：在约旦城市废水中的生化需氧量，化学需氧量，总悬浮固体，NH4等污染物的浓度很高，所以它是一个较大的浪费。评估了四个污水处理厂的性能，常规和改良活性污泥表现出良好的性能，而低水质则是通过稳定塘产生的。活性污泥污水处理厂的出水水质符合约旦标准。为了防止其对人类健康和环境的影响，在重复使用前，二级出水需要进行深度处理。 关键词：废水，处理厂，水回用，废水特点，废水处理，约旦 前言 约旦人口迅速增加，在1950年到2006年从58万增长到560万。这一增长导致每年提高 3.1％的增长速度，并且从1948年巴勒斯坦连续移民，90年代从1967年科威特开始移民（统计处2006年）。约旦多年来一直面临着水资源短缺的问题，提高水资源的利用效率作为其努力的重要组成部分，从而来处理水资源短缺的问题。总平均降水总量约为8.5 × 109立方米/年，但这一数量的92％是通过蒸发损失掉的（铝Zboon，2002）。耗水量的增加，是人口增长和发展项目的必然结果，而水资源的有效利用却是年复一年的被限制。在2000年，每年的需水量，估计为1100万立方米，而从各种渠道的可供水量（地表水和地下水）却小于850 万立方米，这表明了250万立方米的缺水问题。这种水资源的短缺同时也影响了个人消费。例如，在1998年耗水量约为160m3/capita/y，预计在2020年将下降到90m3/capita/y，这是一个非常低的比较对于人均消费水平在1000立方米/年（铝Zboon，2002）城市农业需水量占总用水量的73％，而22％的水是用于国内需求，只有5％是用于工业部门（WAJ，2006）。 这种水资源的需求增加与限制相结合导致水资源的可利用量的发展。目前，世界各地的废水资源的再利用促进了废水有限水资源和
外文翻译 原文：The open system merit of Computer Numerical Control The open system merit is the system simple, the cost low, but the shortcoming is the precision is low. The reverse gap, the guide screw pitch error, stop inferiorly can affect the pointing accuracy by mistake. Following several kind of improvements measure may cause the pointing accuracy distinct improvement. 1. reverse gap error compensates The numerical control engine bed processing cutting tool and the work piece relative motion is depends upon the drive impetus gear,the guide screw rotation, thus the impetus work floor and so on moves the part to produce moves realizes. As traditional part gear, guide screw although the manufacture precision is very high, but always unavoidably has the gap. As a result of this kind of gap existence, when movement direction change, starts the section time to be able to cause inevitably actuates the part wasting time, appears the instruction pulse to push the motionless functional element the aspect. This has affected the engine bed processing precision, namely the instruction pulse and actual enters for the step does not tally,has the processing error therefore, the split-ring numerical control system all establishes generally has the reverse gap error compensatory function, with by makes up which wastes time the step reverse gap difference compensates is first actual reverse enters for the error, converts the pulse equivalent number it, compensates the subroutine as the gap the output, when the computer judgment appears when instruction for counter motion, transfers the gap to compensate the subroutine immediately, compensates the pulse after the output to eliminate the reverse gap to carry on again normally inserts makes up the movement. 2. often the value systematic characteristic position error compensates A kind of storehouse by transfers for the designer. Like this in the components design stage, the designer only must input the characteristic the parameter, the system direct production characteristic example model: We must save the related characteristic class in the database the structure information, the database table collection are use in saving this part of related information. According to the characteristic type definition need, we defined the characteristic class code table, the
Programmable logic controller A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result. 1.History The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay. In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner. One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84
污水处理英文翻译解析 河流污水处理的相关论述 1 前言 随着工业化和城市化的发展，水环境污染、水资源紧缺日益严重，水污染控制、水环境保护已刻不容缓。我国现在新建城市或城区采用雨污分流制，但老城市或老城区大多仍然是雨污合流的排水体制。许多合流污水是直接排放到水体。而将旧合流制改为分流制，受现状条件限制大许多。老城区建成年代较长，地下管线基本成型，地面建筑拥挤，路面狭窄，旧合流制改分流制难度较大。合流污水的一大特点是旱季和雨季的水质、水量变化大，雨季污水 BOD 浓度低，不利于生化处理。国家提出 2010 的我国城市污水处理率要求达到 40%, 因此研究有效的合流污水处理方法对加快城市污水处理步伐具有重要的意义。本文针对合流污水处理的有关情况，谈一些个人看法。 2 污水处理工艺要求 我国目前不少城市，新城区与老城区并存，合流制与分流制并存。因此，新建或扩建的污水处理厂，在满足城市总体规划和排水规划需要的同时，还应能达到如下要求: 1. 具备接纳旧城区合流污水的能力，具有较强的适应冲击负荷的能力。污水处理厂污水来源包括两部分，一是新城区分流污水，二是老城区合流污水。与合流污水相比，分流污水水质、水量变化幅度小得多，对污水处理厂调节缓冲的要求小得多。对于合流污 水，降雨前期因雨水冲刷街区，合流污水较脏，但水量相对较小，降雨后期水量较大，但污水中有机物浓度相对较小。因此，降雨前期合流污水，可考虑与分流污水一起经预处理后进入污水处理构筑物。降雨后期合流污水，除一部
分与分流污水一起经污水预处理构筑物进入污水处理构筑物外，另一部分可考虑通过雨污溢流构筑物进入雨污溢流沉定池后排入附近水体。为了对进入污水处理构筑物的合流污水高峰流量、水质波动进行缓冲调节，污水处理构筑物前端可设缓冲调节池以均衡水质、储存水量。 2. 具有可靠的 BOD、 COD、 SS 去除功能及氮磷去除功能，保证最终出水水质稳定。通常情况下，城市污水中难降解有机物较少， BOD、 COD 去除比较容易实现，而氮磷去除则较复杂。我国现行的污水排放标准对污水处理厂出水氮磷指标有严格的要求，故城市污水处理都必须达到氮磷的有效去除。在现行城市污水脱氮除磷工艺中， A2/0 采用较为广泛。针对 A2/0 工艺存在的问题目前出现了许多改进工艺，每种工艺又都存在各自的特点和局限。由于合流污水引起的水质、水量波动较大，对污水厂各处理单元产生冲击，为了适应受纳水体的要求，为使 BOD、COD 等指标进一步降低，进一步去除污水中的细菌及氮、磷等植物性营养物质，在污水厂与受纳水体之间可设氧化塘。 3. 具有灵活多变的运行方式，可根据收集的污水量、进水水质以及季节变化调整运行方式。常规 A2/0 工艺，很难做到灵活方便地调整运行方式。但 A2/0工艺从构成原理上讲，是在曝气段前 加厌氧段和缺氧段。这一原理用于氧化沟技术，便可形成各种适应不同水质、水量、季节变化的运行方式。污水厂可根据实际情况设两个以上的氧化沟，每个沟设一定数量的水力推进器，池底均匀分布微孔爆气器。通过调整氧化沟污水进水管阀门、曝气器的开及关的区域、内回流比大小、污泥回流比大小及水力推进器运行个数，便可形成串联、并联等若干种运行方式。每种运行方式具有各自区域大小不同的厌氧段、缺氮段、曝气段。当旱季污水量小则采用串联运行方式，雨季污水量大，则采用并联运行方式。夏季温度高，硝化反应速度快，则采用具有较小曝气区域、较小硝化段的运行方式，相应反硝化区域
附录Ⅰ： Wastewater Biological Treatment Processes The objective of wastewater treatment is to reduce the concentration of specific pollutants to the level at which the discharge of the effluent will not adversely affect the environment or pose a health threat. Moreover , reduction of these constituents need only be to some required level. For any given wastewater in a specific location , the degree and type of treatment are variables that require engineering decisions . often the degree of treatment depends on the assimilative capacity of the receiving water . DO sag curves can indicate how much BOD must be removed from wastewater so that the DO of receiving water is not depressed too far . The amount of BOD that must be removed is an effluent standard and dictates in large part the type of wastewater treatment required . To facilitate the discussion of wastewater , assume a “ typical wastewater ”and assume further that the effluent from this wastewater treatment must meet the following effluent standards : BOD≤15mg/L SS≤15mg/L P≤1mg/L Additional effluent standard could have been established , but for illustrative purposes we consider only these three . The treatment system selected to achieve these effluent standards includes 1. Primary treatment : physical processes that nonhomogenizable solids and homogenize the remaining effluent . 2. Secondary treatment : biological process that remove most of the biochemical demand for oxyen . 3. Tertiary treatment : physical , biological , and chemical processes to remove nutrients like phosphorus and inorganic pollutants , to deodorize and decolorize effluent water , and to carry out further oxidation .
毕业论文（设计）外文翻译 题目：可编程逻辑控制器技术 系部名称：信息工程系专业班级： 学生姓名：学号： 指导教师：教师职称： 2014 年3 月XX 日
译文 可编程逻辑控制器技术 引言 PLC（可编程逻辑控制器）实际是一个工业控制系统（近来我们看到更多的是用处理器来取代微控制器），在软件和硬件都配备的条件下，适合应用于工业环境。PLC 的发明是相当必要的，它代替了传统的依靠由继电接触器电路来控制电机。PLC 的工作原理是根据它的输入信号和工作状态来确定输出。用户通常是通过软件或编程输入一个程序，来输出所需要的结果。 如图 8-1 所示，PLC 是由典型的黑色构件组成。特别需要注意的是它的输入和输出， 因为在这些模块上，工业环境会给 CPU 一个输入线，所以很有必要将 CPU 模块隔离以保护其免遭有害的影响。程序单元通常是用计算机来编写程序（一般是梯形图）。 1.1CPU 的中央处理单元 中央处理单元（CPU）是一个 PLC 的主控制器。一般 CPU 本身是一个微控制器。通常这些都是 8 位微控制器，如 8051 ，现在的这些是 16 位和 32 位微控制器。潜规则是，你会发现用在 PLC 控制器上的微控制器多数是由日本生产的日立和富士通，欧洲的西门子控制器，和美国的摩托罗拉微控制器。CPU 也负责通讯，与 PLC 控制器的其它部分相互联系，如程序执行，内存操作，监督输入和设置输出。PLC 控制器拥有复杂的程序用于内存检查，以确保 PLC 内存不被损坏（内存检查是为了安全原因而作出的）。一般来说，CPU 单元多数用来检查 PLC 控制器本身，所以有可能出现的错误很早就会被发现。你可以简单地看任何 PLC 控制器,查看错误信号在发光二极管上的种种指示形式。 1.2内存 系统内存（今天主要是在 FLASH 技术上实现）用于一台 PLC 的过程控制系统。除了 这个操作系统它还包含用户程序将梯形图翻译成二进制的形式。 FLASH 存储器的内容仅在 用户程序改变下可以改变。PLC 控制器较早被用来代替闪存，EPROM 存储器代替了那些只能依靠紫外线灯等擦除内存并依靠程序员来编程的 FLASH 存储器。在 FLASH 技术的作用下这个过程被大大的缩短了。重组程序内存通过程序中的串行通讯用于应用程序开发。使用内存被划分成多个具有特殊功能的模块。存储器某些部分用来存储输入状态和输出状态。一个 输入信号的实际状态是用 1 或0 存储在一个特定的存储位。每一个输入信号和输出信号在内存里都有一个位与之相对应。内存的其他部分用来存储用户程序中使用的变量以及变量的内容。例如，定时器的值和计数器的值都将被存储在这部分内存里。 1.3PLC 控制器的编程 PLC 控制器可以通过计算机（常用的方式）进行编程，还可以通过手动编程器（控制台）编程。这实际上意味着如果你有需要的编程软件那么每个 PLC 控制器都可以通过计算机进行编程。今天的传输计算机是非常适合在工厂对 PLC 控制器进行编程的。这对工业有着非常重要的意义。一旦系统被刷新，重新读取正确的程序到 PLC 就很重要。还可以定期检查 PLC 中的程序是否改变了。这有助于避免在工厂车间发生危险状况（部分汽车制造商建立了通信网络，定期检查项目中的 PLC 控制器，以确保执行的程序是正确的）。
(文档含英文原文和中文翻译) 中英文资料对照外文翻译 Catalytic strategies for industrial water re-use Abstract The use of catalytic processes in pollution abatement and resource recovery is widespread and of significant economic importance [R.J. Farrauto, C.H. Bartholomew, Fundamentals of Industrial Catalytic Processes, Blackie Academic and Professional,1997.]. For water recovery and re-use chemo-catalysis is only just starting to make an impact although bio-catalysis is well established [J.N. Horan, BiologicalWastewater Treatment Systems; Theory and Operation, Chichester, Wiley,
1990.]. This paper will discuss some of the principles behind developing chemo-catalytic processes for water re-use. Within this context oxidative catalytic chemistry has many opportunities to underpin the development of successful processes and many emerging technologies based on this chemistry can be considered . Keywords: COD removal; Catalytic oxidation; Industrial water treatment 1.Introduction Industrial water re-use in Europe has not yet started on the large scale. However, with potential long term changes in European weather and the need for more water abstraction from boreholes and rivers, the availability of water at low prices will become increasingly rare. As water prices rise there will come a point when technologies that exist now (or are being developed) will make water recycle and re-use a viable commercial operation. As that future approaches, it is worth stating the most important fact about wastewater improvement–avoid it completely if at all possible! It is best to consider water not as a naturally available cheap solvent but rather, difficult to purify, easily contaminated material that if allowed into the environment will permeate all parts of the biosphere. A pollutant is just a material in the wrong place and therefore design your process to keep the material where it should be –contained and safe. Avoidance and then minimisation are the two first steps in looking at any pollutant removal problem. Of course avoidance may not be an option on an existing plant where any changes may have large consequences for plant items if major flowsheet revision were required. Also avoidance may mean simply transferring the issue from the aqueous phase to the gas phase. There are advantages and disadvantages to both water and gas pollutant abatement. However, it must be remembered that gas phase organic pollutant removal (VOC combustion etc.,) is much more advanced than the equivalent water COD removal and therefore worth consideration [1]. Because these aspects cannot be over-emphasised，a third step would be to visit the first two steps again. Clean-up is expensive, recycle and re-use even if you have a cost effective process is still more capital equipment that will lower your return on assets and make the process less financially attractive. At present the best technology for water recycle is membrane based. This is the only technology that will produce a sufficiently clean permeate for chemical process use. However, the technology cannot be used in isolation and in many (all) cases will require filtration upstream and a technique for handling the downstream retentate containing the pollutants. Thus, hybrid technologies are required that together can handle the all aspects of the water improvement process[6,7,8]. Hence the general rules for wastewater improvement are: 1. Avoid if possible, consider all possible ways to minimise.
1 Bit Logic In structi ons 1.1 Overview of Bit Logic In structi ons 1.1.1 Description Bit logic in structi ons work with two digits, 1 and 0. These two digits form the base of a nu mber system called the binary system. The two digits 1 and 0 are called binary digits or bits. In the world of con tacts and coils, a 1 in dicates activated or en ergized, and a 0 in dicates not activated or not en ergized. The bit logic in struct ions in terpret sig nal states of 1 and 0 and comb ine them accord ing to Boolea n logic. These comb in ati ons produce a result of 1 or 0 that is called the “result of logic operati on ” (RLO). The logic operations that are triggered by the bit logic instructions perform a variety of fun cti ons. There are bit logic in structio ns to perform the followi ng fun cti ons: ---| |--- Normally Ope n Co ntact (Address) ---| / |--- Normally Closed Con tact (Address) ---(SAVE) Save RLO into BR Memory XOR Bit Exclusive OR ---()Output Coil ---(# )--- Midli ne Output ---|NOT|--- In vert Power Flow The followi ng in structio ns react to an RLO of 1: ---(S ) Set Coil ---(R ) Reset Coil SR Set-Reset Flip Flop RS Reset-Set Flip Flop Other in structi ons react to a positive or n egative edge tran siti on to perform the followi ng functions: ---(N)--- Negative RLO Edge Detectio n ---(P)--- Positive RLO Edge Detectio n NEG Address Negative Edge Detectio n POS Address Positive Edge Detectio n
河流污水处理的相关论述 1 前言 随着工业化和城市化的发展，水环境污染、水资源紧缺日益严重，水污染控制、水环境保护已刻不容缓。我国现在新建城市或城区采用雨污分流制，但老城市或老城区大多仍然是雨污合流的排水体制。许多合流污水是直接排放到水体。而将旧合流制改为分流制，受现状条件限制大许多。老城区建成年代较长，地下管线基本成型，地面建筑拥挤，路面狭窄，旧合流制改分流制难度较大。合流污水的一大特点是旱季和雨季的水质、水量变化大，雨季污水ＢＯＤ浓度低，不利于生化处理。国家提出2010 的我国城市污水处理率要求达到4０%，因此研究有效的合流污水处理方法对加快城市污水处理步伐具有重要的意义。本文针对合流污水处理的有关情况，谈一些个人看法。 2污水处理工艺要求 我国目前不少城市，新城区与老城区并存, 合流制与分流制并存。因此，新建或扩建的污水处理厂,在满足城市总体规划和排水规划需要的同时, 还应能达到如下要求: 1. 具备接纳旧城区合流污水的能力，具有较强的适应冲击负荷的能力。污水处理厂污水来源包括两部分，一是新城区分流污水，二是老城区合流污水。与合流污水相比,分流污水水质、水量变化幅度小得多，对污水处理厂调节缓冲的要求小得多。对于合流
污水，降雨前期因雨水冲刷街区,合流污水较脏, 但水量相对较小, 降雨后期水量较大，但污水中有机物浓度相对较小。因此, 降雨前期合流污水,可考虑与分流污水一起经预处理后进入污水处理构筑物。降雨后期合流污水，除一部分与分流污水一起经污水预处理构筑物进入污水处理构筑物外, 另一部分可考虑通过雨污溢流构筑物进入雨污溢流沉定池后排入附近水体。为了对进入污水处理构筑物的合流污水高峰流量、水质波动进行缓冲调节，污水处理构筑物前端可设缓冲调节池以均衡水质、储存水量。 2. 具有可靠的BOD、COD、ＳS 去除功能及氮磷去除功能, 保证最终出水水质稳定。通常情况下, 城市污水中难降解有机物较少，BOD、ＣOD 去除比较容易实现,而氮磷去除则较复杂。我国现行的污水排放标准对污水处理厂出水氮磷指标有严格的要求，故城市污水处理都必须达到氮磷的有效去除。在现行城市污水脱氮除磷工艺中，Ａ２／０采用较为广泛。针对Ａ2/0工艺存在的问题目前出现了许多改进工艺，每种工艺又都存在各自的特点和局限。由于合流污水引起的水质、水量波动较大，对污水厂各处理单元产生冲击，为了适应受纳水体的要求, 为使BOD、CＯD 等指标进一步降低,进一步去除污水中的细菌及氮、磷等植物性营养物质，在污水厂与受纳水体之间可设氧化塘。 ３.具有灵活多变的运行方式，可根据收集的污水量、进水水质以及季节变化调整运行方式。常规A2/０工艺,很难做到灵活方便地调整运行方式。但A2／0工艺从构成原理上讲, 是在曝
1 Bit Logic Instructions 1.1 Overview of Bit Logic Instructions 1.1.1 Description Bit logic instructions work with two digits, 1 and 0. These two digits form the base of a number system called the binary system. The two digits 1 and 0 are called binary digits or bits. In the world of contacts and coils, a 1 indicates activated or energized, and a 0 indicates not activated or not energized. The bit logic instructions interpret signal states of 1 and 0 and combine them according to Boolean logic. These combinations produce a result of 1 or 0 that is called the “result of logic operation” (RLO). The logic operations that are triggered by the bit logic instructions perform a variety of functions. There are bit logic instructions to perform the following functions: ---| |--- Normally Open Contact (Address) ---| / |--- Normally Closed Contact (Address) ---(SAVE) Save RLO into BR Memory XOR Bit Exclusive OR ---( ) Output Coil ---( # )--- Midline Output ---|NOT|--- Invert Power Flow The following instructions react to an RLO of 1: ---( S ) Set Coil ---( R ) Reset Coil SR Set-Reset Flip Flop RS Reset-Set Flip Flop Other instructions react to a positive or negative edge transition to perform the following functions: ---(N)--- Negative RLO Edge Detection ---(P)--- Positive RLO Edge Detection NEG Address Negative Edge Detection POS Address Positive Edge Detection
附录 Abstract: Programmable controller in the field of industrial control applications, and PLC in the application process, to ensure normal operation should be noted that a series of questions, and give some reasonable suggestions. Key words: PLC Industrial Control Interference Wiring Ground Proposal Description Over the years, programmable logic controller (hereinafter referred to as PLC) from its production to the present, to achieve a connection to the storage logical leap of logic; its function from weak to strong, to achieve a logic control to digital control of progress; its applications from small to large, simple controls to achieve a single device to qualified motion control, process control and distributed control across the various tasks. PLC today in dealing with analog, digital computing, human-machine interface and the network have been a substantial increase in the capacity to become the mainstream of the field of control of industrial control equipment, in all walks of life playing an increasingly important role. ⅡPLC application areas Currently, PLC has been widely used in domestic and foreign steel, petroleum, chemical, power, building materials, machinery manufacturing, automobile, textile, transportation, environmental and cultural entertainment and other industries, the use of mainly divided into the following categories: 1. Binary logic control Replace traditional relay circuit, logic control, sequential control, can be used to control a single device can also be used for multi-cluster control and automation lines. Such as injection molding machine, printing machine, stapler machine, lathe, grinding machines, packaging lines, plating lines and so on. 2. Industrial Process Control In the industrial production process, there are some, such as temperature, pressure, flow, level and speed, the amount of continuous change (ie, analog), PLC using the appropriate A / D and D / A converter module, and a variety of control algorithm program to handle analog, complete closed-loop control. PID closed loop control system adjustment is generally used as a conditioning method was more. Process control in metallurgy, chemical industry, heat treatment, boiler control and so forth have a very wide range of applications 3. Motion Control PLC can be used in a circular motion or linear motion control. Generally use a dedicated motion control module, for example a stepper motor or servo motor driven single-axis or multi-axis position control module, used in a variety of machinery, machine tools, robots, elevators and other occasions. 4. Data Processing PLC with mathematics (including matrix operations, functions, operation, logic operation), data transfer, data conversion, sorting, look-up table, bit manipulation functions, you can complete the data collection, analysis and processing.Data