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1、外文文献原稿和译文原 稿About Programmable Logiccontrollers（PLCs） PLCs (programmable controller) is used in a variety of automatic control system and process control hub.They contain multiple input and output, input and output is used to transistors and other circuit, analog switch and relay to control the equi
2、pment.PLC software interface, standard calculator interface, specialized language programming and network equipment. Programmable logic controller I/O channel rules including all input output contact and contact, to expand capacity and the largest number of channels.Contact number is the sum of inpu
3、t and output points.PLC can specify any combination of these values.Extension units can be stack or connected to each other to increase the total control.The largest number of channels are in an extension system, the total number of maximum input and output channels.PLC system rules include scanning
4、 time, number of instructions, data storage and storage program.Scan time is used to monitor input and output module of PLC need time.Standard operation instruction is used in PLC software.Data storage is the ability to store data.Program memory is the ability to control software. Used for programma
5、ble controller input devices including DC, AC, intermediate relay, thermocouple, RTD, frequency or pulse, transistors and interrupt signal input;Output devices include DC, AC, intermediate relay, frequency or pulse, transistor, three-terminal two-way thyristor switch components;PLC programming equip
6、ment including control panel, handle and computer. Programmable control is used to control a variety of software programming language.These languages including iec61131-3, sequential table (SFC), action block diagram (FBD), ladder diagram (LD), and the structure of the text (ST), instruction sequenc
7、es (IL), relay ladder diagram (RIL), flow charts, C language and Basic language.Iec61131-3 programming environment can support five languages, with international standards to regulate, SFC, respectively, FBD, LD, ST and IL.This allows more vendor compatibility and a variety of languages.SFC is a kin
8、d of graph language, it provides the programming in order to cooperate, can support the order selection and tied for choice, to choose between them.Runtime FBD with a big, established the complicated process, in the form of graphs.Standard mathematical and logical operation can be combined with user
9、 interaction and interface operation.LD is suitable for discrete control and interlock logic diagram language.It is fully compatible with FBD on discrete control.ST is a kind of text language, used for complex mathematical and computational process, language is not applicable to chart.IL is similar
10、to the combination of coding low-level languages.It is used in relatively simple logical instructions.Relay ladder diagram and ladder diagram is used for programmable controller is an important programming language.Ladder diagram programming is designed to relay logic diagram representation of the p
11、rogram.Flow chart is a graphic language, for use in a controller or operations described in the order of application software, it is used to establish a standard component of recycled runtime.C language is a high-level programming language, suitable for processing the most complicated calculation, a
12、 continuous data acquisition task.It typically run in PC debugging.BASIC language is used to handle the number of consecutive data acquisition and interface operation of high-level language. Programmable controller also specification of many computer interface equipment, network rules and characteri
13、stics.PLC energy equipment and running environment is also very important.The development history of programmable controller In 1968, general motors (GM), according to the needs of the development of the market situation and put forward the many varieties, small batch, new car brand model strategy.T
14、o implement this strategy, relying on the original industrial control device obviously not, and there must be a kind of new industrial control device, it can be with the change of the products, flexible and easily change control scheme to difficult to meet the different requirements of control. In 1
15、969, the famous American digital equipment corporation (DEC) according to the function requirements of GM, developed the new industrial control device, and the GM of a vehicle to run automated production line for the first time to succeed.According to this new type of industrial control devices can
16、be programmed to change control scheme this characteristic, and the situation of the specialized for Logic control, says the new industrial control device for the Programmable control (Programmable Logic Controller), hereinafter referred to as PLC. From 1968 to now, the PLC has experienced four generation: most of the first generation of PLC with a machine development, with the core memory storage, only the logic control function.In the
