PLC英文文献+翻译

自动化专业本科毕业设计英文翻译

学院(部)：

专业班级：

学生姓名：

指导教师：

年月日

Programmable Logic Controller

ONE：PLC overview

Programmable controller is the first in the late1960s in the United States,then called PLC programmable logic controller(Programmable Logic Controller)is used to replace relays.For the implementation of the logical judgment, timing, sequence number, and other control functions. The concept is presented PLC General Motors Corporation. PLC and the basic design is the computer functional improvements,flexible,generic and other advantages and relay control system simple and easy to operate, such as the advantages of cheap prices combined controller hardware is standard and overall.According to the practical application of target software in order to control the content of the user procedures memory controller,the controller and connecting the accused convenient target.

In the mid-1970s, the PLC has been widely used as a central processing unit microprocessor,import export module and the external circuits are used, large-scale integrated circuits even when the Plc is no longer the only logical (IC) judgment functions also have data processing, PID conditioning and data communications functions.International Electro technical Commission(IEC)standards promulgated programmable controller for programmable controller draft made the following definition: programmable controller is a digital electronic computers operating system,specifically for applications in the industrial design environment. It used programmable memory, used to implement logic in their internal storage operations, sequence control, timing, counting and arithmetic operations, such as operating instructions,and through digital and analog input and output, the control of various types of machinery or production processes.Programmable controller and related peripherals, and industrial control systems easily linked to form a whole, to expand its functional design. Programmable controller for the user,is a non-contact equipment,the procedures can be changed to change production processes. The programmable controller has become a powerful tool for factory automation, widely popular replication.

Programmable controller is user-oriented industries dedicated control computer, with many distinctive features.

First, high reliability,anti-interference capability;

Second，programming visual, simple;

Third,adaptability good;

Fourth functional improvements,strong functional interface. TWO：History of PLC

Programmable Logic Controllers(PLC), a computing device invented by Richard E.Morley in 1968,have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities,and many others.At that time, the PLC replaced the hardwired logic with soft-wired logic or so-called relay ladder logic(RLL),a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6days[Moody and Morley, 1999].

Although PC based control has started to come into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price,and superior reliability in harsh environments. Moreover,according to a study on the PLC market of Frost and Sullivan [1995],an increase of the annual sales volume to 15 million PLC per year with the hardware value of more than8 billion US dollars has been predicted,though the prices of computing hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a5-billion industry at the present time.

Though PLCs are widely used in industrial practice,the programming of PLC based control systems is still very much relying on trial-and-error.Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating

If houses were built like software projects,a single woodpecker could destroy civilization.”

Particularly,practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder

logic programs. Though the hardware costs of PLC are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLC can be used.

In general,the productivity in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice.Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLC-programming requires a simultaneous consideration of hardware and software. The software design becomes,thereby, more and more the major cost driver.In many industrial design projects,more than of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs.

In addition,current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. A further problem, impelling the need for a systematic design methodology,is the increasing software complexity in large-scale projects.

The objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves high-level description based on state transition models that treat automation control systems as discrete event systems, a stepwise design process,and set of design rules providing guidance and measurements to achieve a successful design.The tangible outcome of this research is to find a way to reduce the uncertainty in managing the control software development process, that is, reducing programming and debugging time and their variation,increasing flexibility of the automation systems, and enabling software reusability through modularity. The goal is to overcome shortcomings of current programming strategies that are based on the experience of the individual software developer.

Three：now of PLC

From the structure is divided into fixed PLC and Module PLC, the two kinds of PLC including CPU board,I/O board, display panel, memory block, power, these elements into a do not remove overall.

Module type PLC including CPU module, I/O modules, memory,the power modules, bottom or a frame, these modules can be according to certain rules combination configuration.

In the user view,a detailed analysis of the CPU's internal unnecessary, but working mechanism of every part of the circuit.The CPU control works,by it reads CPU instruction, interprets the instruction and executes instructions. But the pace of work by shock signal control.

Unit work under the controller command used in a digital or logic operations.In computing and storage register of computation result,it is also among the controller command and work. CPU speed and memory capacity is the important parameters fot PLC.its determines the PLC speed of work, IO PLC number and software capacity,so limits to control size.

Central Processing Unit (CPU)is the brain of a PLC controller.CPU itself is usually one of the microcontrollers.Aforetime these were 8-bit microcontrollers such as 8051, and now these are16-and 32-bit microcontrollers.Unspoken rule is that you’ll find mostly Hitachi and Fujicu microcontrollers in PLC controllers by Japanese makers, Siemens in European controllers, and Motorola microcontrollers in American ones. CPU also takes care of communication,interconnectedness among other parts of PLC controllers,program execution, memory operation, overseeing input and setting up of an output.

System memory (today mostly implemented in FLASH technology) is used by a PLC for a process control system. Aside form. this operating system it also contains a user program translated foram ladder diagram to a binary form. FLASH memory contents can be changed only in case where user program is being changed. PLC controllers were used earlier instead of PLASH memory and have had EPROM memory instead of FLASH memory which had to be erased with UV lamp and programmed on programmers.With the use of FLASH technology this process was greatly shortened. Reprogramming a program memory is done through a serial cable in a program for application development.

User memory is divided into blocks having special functions. Some parts of a memory are used for storing input and output status.The real

本文来源：https://www.bwwdw.com/article/dknm.html