PLC英文文献+翻译.docx

PLC英文文献+翻译.docx

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PLC英文文献+翻译

自动化专业本科毕业设计英文翻译

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ProgrammableLogicController

ONE：

PLCoverview

Programmablecontrolleristhefirstinthelate1960sintheUnitedStates,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：

HistoryofPLC

ProgrammableLogicControllers（PLC）,acomputingdeviceinventedbyRichardE.Morleyin1968,havebeenwidelyusedinindustryincludingmanufacturingsystems,transportationsystems,chemicalprocessfacilities,andmanyothers.Atthattime,thePLCreplacedthehardwiredlogicwithsoft-wiredlogicorso-calledrelayladderlogic（RLL）,aprogramminglanguagevisuallyresemblingthehardwiredlogic,andreducedtherebytheconfigurationtimefrom6monthsdownto6days[MoodyandMorley,1999].

AlthoughPCbasedcontrolhasstartedtocomeintoplace,PLCbasedcontrolwillremainthetechniquetowhichthemajorityofindustrialapplicationswilladhereduetoitshigherperformance,lowerprice,andsuperiorreliabilityinharshenvironments.Moreover,accordingtoastudyonthePLCmarketofFrostandSullivan[1995],anincreaseoftheannualsalesvolumeto15millionPLCperyearwiththehardwarevalueofmorethan8billionUSdollarshasbeenpredicted,thoughthepricesofcomputinghardwareissteadilydropping.TheinventorofthePLC,RichardEMorley,fairlyconsidersthePLCmarketasa5-billionindustryatthepresenttime.

ThoughPLCsarewidelyusedinindustrialpractice,theprogrammingofPLCbasedcontrolsystemsisstillverymuchrelyingontrial-and-error.Alikesoftwareengineering,PLCsoftwaredesignisfacingthesoftwaredilemmaorcrisisinasimilarway.Morleyhimselfemphasizedthisaspectmostforcefullybyindicating

Ifhouseswerebuiltlikesoftwareprojects,asinglewoodpeckercoulddestroycivilization.”

Particularly,practicalproblemsinPLCprogrammingaretoeliminatesoftwarebugsandtoreducethemaintenancecostsofoldladder

logicprograms.ThoughthehardwarecostsofPLCaredroppingcontinuously,reducingthescantimeoftheladderlogicisstillanissueinindustrysothatlow-costPLCcanbeused.

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,reducingprogramminganddebuggingtimeandtheirvariation,increasingflexibilityoftheautomationsystems,andenablingsoftwarereusabilitythroughmodularity.Thegoalistoovercomeshortcomingsofcurrentprogrammingstrategiesthatarebasedontheexperienceoftheindividualsoftwaredeveloper.

Three：

nowofPLC

FromthestructureisdividedintofixedPLCandModulePLC,thetwokindsofPLCincludingCPUboard,I/Oboard,displaypanel,memoryblock,power,theseelementsintoadonotremoveoverall.

ModuletypePLCincludingCPUmodule,I/Omodules,memory,thepowermodules,bottomoraframe,thesemodulescanbeaccordingtocertainrulescombinationconfiguration.

Intheuserview,adetailedanalysisoftheCPU'sinternalunnecessary,butworkingmechanismofeverypartofthecircuit.TheCPUcontrolworks,byitreadsCPUinstruction,interpretstheinstructionandexecutesinstructions.Butthepaceofworkbyshocksignalcontrol.

Unitworkunderthecontrollercommandusedinadigitalorlogicoperations.Incomputingandstorageregisterofcomputationresult,itisalsoamongthecontrollercommandandwork.CPUspeedandmemorycapacityistheimportantparametersfotPLC.itsdeterminesthePLCspeedofwork,IOPLCnumberandsoftwarecapacity,solimitstocontrolsize.

CentralProcessingUnit（CPU）isthebrainofaPLCcontroller.CPUitselfisusuallyoneofthemicrocontrollers.Aforetimethesewere8-bitmicrocontrollerssuchas8051,andnowtheseare16-and32-bitmicrocontrollers.Unspokenruleisthatyou’llfindmostlyHitachiandFujicumicrocontrollersinPLCcontrollersbyJapanesemakers,SiemensinEuropeancontrollers,andMotorolamicrocontrollersinAmericanones.CPUalsotakescareofcommunication,interconnectednessamongotherpartsofPLCcontrollers,programexecution,memoryoperation,overseeinginputandsettingupofanoutput.

Systemmemory（todaymostlyimplementedinFLASHtechnology）isusedbyaPLCforaprocesscontrolsystem.Asideform.thisoperatingsystemitalsocontainsauserprogramtranslatedforamladderdiagramtoabinaryform.FLASHmemorycontentscanbechangedonlyincasewhereuserprogramisbeingchanged.PLCcontrollerswereusedearlierinsteadofPLASHmemoryandhavehadEPROMmemoryinsteadofFLASHmemorywhichhadtobeerasedwithUVlampandprogrammedonprogrammers.WiththeuseofFLASHtechnologythisprocesswasgreatlyshortened.Reprogrammingaprogrammemoryisdonethroughaserialcableinaprogramforapplicationdevelopment.

Usermemoryisdividedintoblockshavingspecialfunctions.Somepartsofamemoryareusedforstoringinputandoutputstatus.Thereal

statusofaninputisstoredeitheras“1”oras“0”inaspecificmemorybit/eachinputoroutputhasonecorrespondingbitinmemory.Otherpartsofmemoryareusedtostorevariablecontentsforvariablesusedinusedprogram.Forexample,timevalue,orcountervaluewouldbestoredinthispartofthememory.

PLCcontrollercanbereprogrammedthroughacomputer（usualway）,butalsothroughmanualprogrammers（consoles）.ThispracticallymeansthateachPLCcontrollercanprogrammedthroughacomputerifyouhavethesoftwareneededforprogramming.Today’stransmissioncomputersareidealforreprogrammingaPLCcontrollerinfactoryitself.Thisisofgreatimportancetoindustry.Oncethesystemiscorrected,itisalsoimportanttoreadtherightprogramintoaPLCagain.ItisalsogoodtocheckfromtimetotimewhetherprograminaPLChasnotchanged.Thishelpstoavoidhazardoussituationsinfactoryrooms（someautomakershaveestablishedcommunicationnetworkswhichregularlycheckprogramsinPLCcontrollerstoensureexecutiononlyofgoodprograms）.

AlmosteveryprogramforprogrammingaPLCcontrollerpossessesvarioususefuloptionssuchas:

forcedswitchingonandoffofthesysteminput/outputs（I/Olines）,programfollowupinrealtimeaswellasdocumentingadiagram.Thisdocumentingisnecessarytounderstandanddefinef