【正文】 n link. These munication links are also often used for HMI devices such as keypads or PCtype workstations. PLC programs are typically written in a special application on a personal puter, then downloaded by a directconnection cable or over a work to the PLC. The program is stored in the PLC either in batterybackedup RAM or some other nonvolatile flash memory. Often, a single PLC can be programmed to replace thousands of relays. Under the IEC 611313 standard, PLCs can be programmed using standardsbased programming languages. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. Initially 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 mon today. IEC 611313 currently defines five programming languages for programmable control systems: FBD (Function block diagram), LD (Ladder diagram), ST 6 (Structured text, similar to the Pascal programming language), IL (Instruction list, similar to assembly language) and SFC (Sequential function chart). These techniques emphasize logical anization of operations. While the fundamental concepts of PLC programming are mon to all manufacturers, differences in I/O addressing, memory anization and instruction sets mean that PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly patible. pared with other control systems PLCs are welladapted to a range of automation tasks. These are typically 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 operational life. PLCs contain input and output devices patible with industrial pilot devices and controls。 外文文獻(xiàn)譯文 設(shè)計 (論文 )題目 : 可編程邏輯控制器 專業(yè)與班級 : 學(xué)生姓名 : 指導(dǎo)教師 : 2021 年 3 月 18 日 1 Programmable logic controller A programmable logic controller (PLC) or programmable controller is a digital puter 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 generalpurpose puters, 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 batterybacked or nonvolatile 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. 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 rewiring of hardwired control panels when production models changed. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was acplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closedloop controllers. The process for updating such facilities for the yearly model changeover 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 hardwired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates39。 eightyfourth project, was the result. Bedford Associates started a new pany 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 Modicon39。 little electrical design is required, and the design problem