外文文献翻译可编程逻辑控制器PLCWord格式文档下载.docx
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外文文献翻译可编程逻辑控制器PLC@#@可编程逻辑控制器PLC外文文献翻译@#@(含:
@#@英文原文及中文译文)@#@文献出处:
@#@KinnaD.ProgrammableLogicControllers(PLC)[J].FusionEngineering&@#@Design,2015,2(12):
@#@72-83.@#@英文原文@#@ProgrammableLogicControllers(PLC)@#@KinnaDarl@#@1Motivation@#@ProgrammableLogicControllers(PLC),acomputingdeviceinventedbyRichardE.Morleyin1968,havebeenwidelyusedinindustryincludingmanufacturingsystems,transportationsystems,chemicalprocessfacilities,andmanyothers.Atthattime,thePLCreplacedthehardwiredlogicwithsoft-wiredlogicorso-calledrelayladderlogic(RLL),aprogramminglanguagevisuallyresemblingthehardwiredlogic,andreducedtherebytheconfigurationtimefrom6monthsdownto6days[MoodyandMorley,1999].@#@AlthoughPCbasedcontrolhasstartedtocomeintoplace,PLCbasedcontrolwillremainthetechniquetowhichthemajorityofindustrialapplicationswilladhereduetoitshigherperformance,lowerprice,andsuperiorreliabilityinharshenvironments.Moreover,accordingtoastudyonthePLCmarketofFrostandSullivan[1995],anincreaseoftheannualsalesvolumeto15millionPLCsperyearwiththehardwarevalueofmorethan8billionUSdollarshasbeenpredicted,thoughthepricesofcomputinghardwareissteadilydropping.TheinventorofthePLC,RichardEMorley,fairlyconsidersthePLCmarketasa5-billionindustryatthepresenttime.@#@Ingeneral,theproductivityingeneratingPLCisfarbehindcomparedtootherdomains,forinstance,VLSIdesign,whereefficientcomputeraideddesigntoolsareinpractice.ExistentsoftwareengineeringmethodologiesarenotnecessarilyapplicabletothePLCbasedsoftwaredesignbecausePLC-programmingrequiresasimultaneousconsiderationofhardwareandsoftware.Thesoftwaredesignbecomes,thereby,moreandmorethemajorcostdriver.Inmanyindustrialdesignprojects,morethan50%ofthemanpowerallocatedforthecontrolsystemdesignandinstallationisscheduledfortestinganddebuggingPLCprograms[Rockwell,1999].@#@PLCs(programmablelogiccontrollers)arethecontrolhubsforawidevarietyofautomatedsystemsandprocesses.Theycontainmultipleinputsandoutputsthatusetransistorsandothercircuitrytosimulateswitchesandrelaystocontrolequipment.Theyareprogrammableviasoftwareinterfacedviastandardcomputerinterfacesandproprietarylanguagesandnetworkoptions.@#@ProgrammablelogiccontrollersI/Ochannelspecificationsincludetotalnumberofpoints,numberofinputsandoutputs,abilitytoexpand,andmaximumnumberofchannels.Numberofpointsisthesumoftheinputsandtheoutputs.PLCsmaybespecifiedbyanypossiblecombinationofthesevalues.Expandableunitsmaybestackedorlinkedtogethertoincreasetotalcontrolcapacity.Maximumnumberofchannelsreferstothemaximumtotalnumberofinputandoutputchannelsinanexpandedsystem.@#@PLCsystemspecificationstoconsiderincludescantime,numberofinstructions,datamemory,andprogrammemory.ScantimeisthetimerequiredbythePLCtocheckthestatesofitsinputsandoutputs.Instructionsarestandardoperations(suchasmathfunctions)availabletoPLCsoftware.Datamemoryisthecapacityfordatastorage.Programmemoryisthecapacityforcontrolsoftware.@#@Programmablelogiccontrollersuseavarietyofsoftwareprogramminglanguagesforcontrol.TheseincludeIEC61131-3,sequentialfunctionchart(SFC),functionblockdiagram(FBD),ladderdiagram(LD),structuredtext(ST),instructionlist(IL),relayladderlogic(RLL),flowchart,C,andBasic.TheIEC61131-3programmingenvironmentprovidessupportforfivelanguagesspecifiedbytheglobalstandard:
@#@SequentialFunctionChart,FunctionBlockDiagram,LadderDiagram,StructuredText,andInstructionList.Thisallowsformulti-vendorcompatibilityandmulti-languageprogramming.SFCisagraphicallanguagethatprovidescoordinationofprogramsequences,supportingalternativesequenceselectionsandparallelsequences.FBDusesabroadfunctionlibrarytobuildcomplexproceduresinagraphicalformat.Standardmathandlogicfunctionsmaybecoordinatedwithcustomizablecommunicationandinterfacefunctions.LDisagraphiclanguagefordiscretecontrolandinterlockinglogic.ItiscompletelycompatiblewithFBDfordiscretefunctioncontrol.STisatextlanguageusedforcomplexmathematicalproceduresandcalculationslesswellsuitedtographicallanguages.ILisalow-levellanguagesimilartoassemblycode.Itisusedinrelativelysimplelogicinstructions.RelayLadderLogic(RLL),orladderdiagrams,istheprimaryprogramminglanguageforprogrammablelogiccontrollers(PLCs).Ladderlogicprogrammingisagraphicalrepresentationoftheprogramdesignedtolooklikerelaylogic.FlowChartisagraphicallanguagethatdescribessequentialoperationsinacontrollersequenceorapplication.Itisusedtobuildmodular,reusablefunctionlibrar