资源描述：
《可编程序控制器 外文文献翻译大学论文.doc》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。
1、英语原文：ProgrammablelogiccontrollerAprogrammablelogiccontroller(PLC)orsimplyprogrammablecontrollerisadigitalcomputerusedforautomationofindustrialprocesses,suchascontrolofmachineryonfactoryassemblylines.Unlikegeneral-purposecomputers,thePLCisdesignedformultipleinputs
2、andoutputarrangements,extendedtemperatureranges,immunitytoelectricalnoise,andresistancetovibrationandimpact.Programstocontrolmachineoperationaretypicallystoredinbattery-backedornon-volatilememory.APLCisanexampleofarealtimesystemsinceoutputresultsmustbeproducedinr
3、esponsetoinputconditionswithinaboundedtime,otherwiseunintendedoperationwillresult..FeaturesThemaindifferencefromothercomputersisthatPLCarearmoredforseverecondition(dust,moisture,heat,cold,etc)andhavethefacilityforextensiveinput/output(I/O)arrangements.Theseconnec
4、tthePLCtosensorsandactuators.PLCreadlimitswitches,analogprocessvariables(suchastemperatureandpressure),andthepositionsofcomplexpositioningsystems.Someevenusemachinevision.Ontheactuatorside,PLCoperateelectricmotors,pneumaticorhydrauliccylinders,magneticrelaysorsol
5、enoids,oranalogoutputs.Theinput/outputarrangementsmaybebuiltintoasimplePLC,orthePLCmayhaveexternalI/OmodulesattachedtoacomputernetworkthatplugsintothePLC.PLCwereinventedasreplacementsforautomatedsystemsthatwouldusehundredsorthousandsofrelays,camtimers,anddrumsequ
6、encers.Often,asinglePLCcanbeprogrammedtoreplacethousandsofrelays.Programmablecontrollerswereinitiallyadoptedbytheautomotivemanufacturingindustry,wheresoftwarerevisionreplacedthere-wiringofhard-wiredcontrolpanelswhenproductionmodelschanged.12ManyoftheearliestPLCex
7、pressedalldecisionmakinglogicinsimpleladderlogicwhichappearedsimilartoelectricalschematicdiagrams.Theelectricianswerequiteabletotraceoutcircuitproblemswithschematicdiagramsusingladderlogic.Thisprogramnotationwaschosentoreducetrainingdemandsfortheexistingtechnicia
8、ns.OtherearlyPLCusedaformofinstructionlistprogramming,basedonastack-basedlogicsolver.ThefunctionalityofthePLChasevolvedovertheyearstoincludesequentialrelaycont
