plc外文文献译文

1、Programmable logic controllerA programmable logic controller (PLC) is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusementrides, or lighting fixtures. PLC is used in many industries and machines.The PLC was invented

2、in response to the needs of the American automotive manufacturing industry. 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. In

3、1968 GM Hydramatic issued a request for proposal for an electronic replacement for hard-wired relay 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, an

4、d servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. 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 of the very first 084 models that was presented to Modicon by GM, wh

5、en the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range until the 984 made its appearance.Early PLCs were designed to replace relay logic systems.These PLCs were programmed in "ladder logic", which strongly res

6、embles a schematic diagram of relay logic. Other early PLCs used a form of instruction list programming, based on a stack-based logic solver.Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and C. Another method is State Lo

7、gic, a very high-level programming language designed to program PLCs based on state transition diagrams.The functionality of the PLChave sequential relay control, motion control, process control, distributed control systems and the practicality of these desktop computer based logic controllers, it i

8、s 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 temperature,In more recent years, s

9、mall products called PLRs (programmable logic relays), are used in light industry where only a few points of I/O . a few signals coming in from the real world and a few going out) are involved,and low cost is desired.Popular names include PICO Controller, NANO PLC, and other namesimplying very small

10、 controllers. the PLRsare usually not modular 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 pared with other control systemsPLCs are well-adapted to a range of automation tasks. These are t

11、ypically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operationallife. PLCs contain input and output devices compatible with

12、industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLCis low compared to the cost of a specific custom-built c

13、ontroller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a "generic" solution, and where the non-recurring engineering charges are spread over thousands

14、 or millions of units.A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over manysales, and where the end-user w

15、ould not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit busses economically use PLCs instead of custom-designed controls, bec

16、ause the volumes are low and the development cost would be uneconomic.Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNCmachine) can be used to i

17、nstruct machine movements.PLCsmayinclude 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. Historically PLCswere usually

18、configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has become less distinct.PLCs have similar functionalit

19、y as Remote Terminal Units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomesmore powerful and cheaper, RTUs, PLCs and DCSs are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features and vice v

20、ersa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development spects for PLC.The main difference from other computers is that P

21、LCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Someuse machine vis

22、ion. Onthe 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 simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.scale

23、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 PLCshave a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O m

24、odules is customised for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special high speed serial I/O link is used so that racks can be distributed away from the processor, reducing the wiring costs for large plant

25、erfacePLCs 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 graphical touch screens. More complex systems use a programming and mon

26、itoring software installed on a computer, with the PLC connected via a communication interface.PLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or Ethernet. Modbus, BACnet or DF1is usually included as one of the communications protocols. Other options include var

27、ious fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protocols.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

28、web browser.PLCs used in larger I/O systems mayhave peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link.These communication links are also often used f

29、or HMI devices such as keypads or PC-type workstations.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、游乐设施或照明的装置。 可编程控制器可在许多工业和机器中使用。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1968年GM Hydramatic发布通用汽车公

30、司的提议，电子替 代布线中继系统。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。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。这是专门为通用汽车服务的，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。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。其他早期 的可编程控制器使用指令列表

31、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 BASICS 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。3 .功能PLC的功能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。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。在近些年，小产品称为 PLR （可编程逻辑继电器）已经应用于轻 工业，

32、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。俗名包括 PICO控制器、纳米PLCffi其他的 小控制器。PLR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。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（PL。

33、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。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。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