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1、外文文献原稿和译文原稿AboutProgrammableLogiccontrollers（PLCs）PLCs(programmablecontroller)isusedinavarietyofautomaticcontrolsystemandprocesscontrolhub.Theycontainmultipleinputandoutput,inputandoutputisusedtotransistorsandothercircuit,analogswitchandrelaytocontroltheequipment.PLCsoftwar
2、einterface,standardcalculatorinterface,specializedlanguageprogrammingandnetworkequipment.ProgrammablelogiccontrollerI/Ochannelrulesincludingallinputoutputcontactandcontact,toexpandcapacityandthelargestnumberofchannels.Contactnumberisthesumofinputandoutputpoints.PLCcanspecif
3、yanycombinationofthesevalues.Extensionunitscanbestackorconnectedtoeachothertoincreasethetotalcontrol.Thelargestnumberofchannelsareinanextensionsystem,thetotalnumberofmaximuminputandoutputchannels.PLCsystemrulesincludescanningtime,numberofinstructions,datastorageandstoragepr
4、ogram.ScantimeisusedtomonitorinputandoutputmoduleofPLCneedtime.StandardoperationinstructionisusedinPLCsoftware.Datastorageistheabilitytostoredata.Programmemoryistheabilitytocontrolsoftware.UsedforprogrammablecontrollerinputdevicesincludingDC,AC,intermediaterelay,thermocoupl
5、e,RTD,frequencyorpulse,transistorsandinterruptsignalinput;OutputdevicesincludeDC,AC,intermediaterelay,frequencyorpulse,transistor,three-terminaltwo-waythyristorswitchcomponents;PLCprogrammingequipmentincludingcontrolpanel,handleandcomputer.Programmablecontrolisusedtocontrol
6、avarietyofsoftwareprogramminglanguage.Theselanguagesincludingiec61131-3,sequentialtable(SFC),actionblockdiagram(FBD),ladderdiagram(LD),andthestructureofthetext(ST),instructionsequences(IL),relayladderdiagram(RIL),flowcharts,ClanguageandBasiclanguage.Iec61131-3programmingenv
7、ironmentcansupportfivelanguages,withinternationalstandardstoregulate,SFC,respectively,FBD,LD,STandIL.Thisallowsmorevendorcompatibilityandavarietyoflanguages.SFCisakindofgraphlanguage,itprovidestheprogramminginordertocooperate,cansupporttheorderselectionandtiedforchoice,toch
8、oosebetweenthem.RuntimeFBDwithabig,establishedthecomplicatedprocess,intheformofgra
