毕业设计论文中英文资料翻译PLC overview

英文资料翻译题目PLCoverview英文原文资料PLCoverviewProgrammablecontrolleristhefirstinthelate1960sintheUnitedStates,thencalledPlcprogrammablelogiccontroller(ProgrammableLogicController)isusedtoreplacerelays.Fortheimplementationofthelogicaljudgment,timing,sequencenumber,andothercontrolfunctions.TheconceptispresentedPlcGeneralMotorsCorporation.Plcandthebasicdesignisthecomputerfunctionalimprovements,flexible,genericandotheradvantagesandrelaycontrolsystemsimpleandeasytooperate,suchastheadvantagesofcheappricescombinedcontrollerhardwareisstandardandoverall.Accordingtothepracticalapplicationoftargetsoftwareinordertocontrolthecontentoftheuserproceduresmemorycontroller,thecontrollerandconnectingtheaccusedconvenienttarget.Inthemid-1970s,thePlchasbeenwidelyusedasacentralprocessingunitmicroprocessor,importexportmoduleandtheexternalcircuitsareused,large-scaleintegratedcircuitsevenwhenthePlcisnolongertheonlylogical(IC)judgmentfunctionsalsohavedataprocessing,PIDconditioninganddatacommunicationsfunctions.InternationalElectrotechnicalCommission(IEC)standardspromulgatedprogrammablecontrollerforprogrammablecontrollerdraftmadethefollowingdefinition:programmablecontrollerisadigitalelectroniccomputersoperatingsystem,specificallyforapplicationsintheindustrialdesignenvironment.Itusedprogrammablememory,usedtoimplementlogicintheirinternalstorageoperations,sequencecontrol,timing,countingandarithmeticoperations,suchasoperatinginstructions,andthroughdigitalandanaloginputandoutput,thecontrolofvarioustypesofmachineryorproductionprocesses.Programmablecontrollerandrelatedperipherals,andindustrialcontrolsystemseasilylinkedtoformawhole,toexpanditsfunctionaldesign.Programmablecontrollerfortheuser,isanon-contactequipment,theprocedurescanbechangedtochangeproductionprocesses.Theprogrammablecontrollerhasbecomeapowerfultoolforfactoryautomation,widelypopularreplication.Programmablecontrollerisuser-orientedindustriesdedicatedcontrolcomputer,withmanydistinctivefeatures.First,highreliability,anti-interferencecapability;Second，programmingvisual,simple;Third,adaptabilitygood;Fourthfunctionalimprovements,strongfunctionalinterface.TWO、HistoryofPLCProgrammableLogicControllers(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.ThoughPLCsarewidelyusedinindustrialpractice,theprogrammingofPLCbasedcontrolsystemsisstillverymuchrelyingontrial-and-error.Alikesoftwareengineering,PLCsoftwaredesignisfacingthesoftwaredilemmaorcrisisinasimilarway.Morleyhimselfemphasizedthisaspectmostforcefullybyindicating`Ifhouseswerebuiltlikesoftwareprojects,asinglewoodpeckercoulddestroycivilization.”Particularly,practicalproblemsinPLCprogrammingaretoeliminatesoftwarebugsandtoreducethemaintenancecostsofoldladderlogicprograms.ThoughthehardwarecostsofPLCsaredroppingcontinuously,reducingthescantimeoftheladderlogicisstillanissueinindustrysothatlow-costPLCscanbeused.Ingeneral,theproductivityingeneratingPLCisfarbehindcomparedtootherdomains,forinstance,VLSIdesign,whereefficientcomputeraideddesigntoolsareinpractice.ExistentsoftwareengineeringmethodologiesarenotnecessarilyapplicabletothePLCbasedsoftwaredesignbecausePLC-programmingrequiresasimultaneousconsiderationofhardwareandsoftware.Thesoftwaredesignbecomes,thereby,moreandmorethemajorcostdriver.Inmanyindustrialdesignprojects,morethanofthemanpowerallocatedforthecontrolsystemdesignandinstallationisscheduledfortestinganddebuggingPLCprograms.Inaddition,currentPLCbasedcontrolsystemsarenotproperlydesignedtosupportthegrowingdemandforflexibilityandreconfigurabilityofmanufacturingsystems.Afurtherproblem,impellingtheneedforasystematicdesignmethodology,istheincreasingsoftwarecomplexityinlarge-scaleprojects.TheobjectiveofthisthesisistodevelopasystematicsoftwaredesignmethodologyforPLCoperatedautomationsystems.Thedesignmethodologyinvolveshigh-leveldescriptionbasedonstatetransitionmodelsthattreatautomationcontrolsystemsasdiscreteeventsystems,astepwisedesignprocess,andsetofdesignrulesprovidingguidanceandmeasurementstoachieveasuccessfuldesign.Thetangibleoutcomeofthisresearchistofindawaytoreducetheuncertaintyinmanagingthecontrolsoftwaredevelopmentprocess,thatis,reducingprogramminganddebug