外文文献译文设计(论文)题目:可编程逻辑控制器专业与班级:学生姓名:指导教师:2010年3月18日ProgrammablelogiccontrollerAprogrammablelogiccontroller(PLC)orprogrammablecontrollerisaHYPERLINK"http://en.wikipedia.org/wiki/Digital_computer"digitalcomputerusedforHYPERLINK"http://en.wikipedia.org/wiki/Automation"automationofHYPERLINK"http://en.wikipedia.org/wiki/Electromechanical"electromechanicalprocesses,suchascontrolofmachineryonfactoryHYPERLINK"http://en.wikipedia.org/wiki/Assembly_line"assemblylines,amusementrides,orlightingfixtures.PLCsareusedinmanyindustriesandmachines.Unlikegeneral-purposecomputers,thePLCisdesignedformultipleinputsandoutputarrangements,extendedtemperatureranges,immunitytoelectricalnoise,andresistancetovibrationandimpact.Programstocontrolmachineoperationaretypicallystoredinbattery-backedorHYPERLINK"http://en.wikipedia.org/wiki/Non-volatile_memory"non-volatilememory.APLCisanexampleofaHYPERLINK"http://en.wikipedia.org/wiki/Real-time_computing"realtimesystemsinceoutputresultsmustbeproducedinresponsetoinputconditionswithinaboundedtime,otherwiseunintendedoperationwillresult.1.HistoryThePLCwasinventedinresponsetotheneedsoftheAmericanautomotivemanufacturingindustry.Programmablelogiccontrollerswereinitiallyadoptedbytheautomotiveindustrywheresoftwarerevisionreplacedthere-wiringofhard-wiredcontrolpanelswhenproductionmodelschanged.BeforethePLC,control,sequencing,andsafetyinterlocklogicformanufacturingautomobileswasaccomplishedusinghundredsorthousandsofHYPERLINK"http://en.wikipedia.org/wiki/Relay"relays,HYPERLINK"http://en.wikipedia.org/wiki/Cam_timer"camtimers,andHYPERLINK"http://en.wikipedia.org/wiki/Drum_sequencer"drumsequencersanddedicatedclosed-loopcontrollers.TheprocessforupdatingsuchfacilitiesfortheyearlymodelHYPERLINK"http://en.wikipedia.org/wiki/Changeover"change-overwasverytimeconsumingandexpensive,asHYPERLINK"http://en.wikipedia.org/wiki/Electrician"electriciansneededtoindividuallyrewireeachandeveryrelay.In1968GMHydramatic(th