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外文翻译-- PLC概述.doc

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外文翻译-- PLC概述.doc

英文原文1PLCOVERVIEWPROGRAMMABLECONTROLLERISTHEFIRSTINTHELATE1960SINTHEUNITEDSTATES,THENCALLEDPLCPROGRAMMABLELOGICCONTROLLERPROGRAMMABLELOGICCONTROLLERISUSEDTOREPLACERELAYSFORTHEIMPLEMENTATIONOFTHELOGICALJUDGMENT,TIMING,SEQUENCENUMBER,ANDOTHERCONTROLFUNCTIONSTHECONCEPTISPRESENTEDPLCGENERALMOTORSCORPORATIONPLCANDTHEBASICDESIGNISTHECOMPUTERFUNCTIONALIMPROVEMENTS,FLEXIBLE,GENERICANDOTHERADVANTAGESANDRELAYCONTROLSYSTEMSIMPLEANDEASYTOOPERATE,SUCHASTHEADVANTAGESOFCHEAPPRICESCOMBINEDCONTROLLERHARDWAREISSTANDARDANDOVERALLACCORDINGTOTHEPRACTICALAPPLICATIONOFTARGETSOFTWAREINORDERTOCONTROLTHECONTENTOFTHEUSERPROCEDURESMEMORYCONTROLLER,THECONTROLLERANDCONNECTINGTHEACCUSEDCONVENIENTTARGETINTHEMID1970S,THEPLCHASBEENWIDELYUSEDASACENTRALPROCESSINGUNITMICROPROCESSOR,IMPORTEXPORTMODULEANDTHEEXTERNALCIRCUITSAREUSED,LARGESCALEINTEGRATEDCIRCUITSEVENWHENTHEPLCISNOLONGERTHEONLYLOGICALICJUDGMENTFUNCTIONSALSOHAVEDATAPROCESSING,PIDCONDITIONINGANDDATACOMMUNICATIONSFUNCTIONSINTERNATIONALELECTROTECHNICALCOMMISSIONIECSTANDARDSPROMULGATEDPROGRAMMABLECONTROLLERFORPROGRAMMABLECONTROLLERDRAFTMADETHEFOLLOWINGDEFINITIONPROGRAMMABLECONTROLLERISADIGITALELECTRONICCOMPUTERSOPERATINGSYSTEM,SPECIFICALLYFORAPPLICATIONSINTHEINDUSTRIALDESIGNENVIRONMENTITUSEDPROGRAMMABLEMEMORY,USEDTOIMPLEMENTLOGICINTHEIRINTERNALSTORAGEOPERATIONS,SEQUENCECONTROL,TIMING,COUNTINGANDARITHMETICOPERATIONS,SUCHASOPERATINGINSTRUCTIONS,ANDTHROUGHDIGITALANDANALOGINPUTANDOUTPUT,THECONTROLOFVARIOUSTYPESOFMACHINERYORPRODUCTIONPROCESSESPROGRAMMABLECONTROLLERANDRELATEDPERIPHERALS,ANDINDUSTRIALCONTROLSYSTEMSEASILYLINKEDTOFORMAWHOLE,TOEXPANDITSFUNCTIONALDESIGNPROGRAMMABLECONTROLLERFORTHEUSER,ISANONCONTACTEQUIPMENT,THEPROCEDURESCANBECHANGEDTOCHANGEPRODUCTIONPROCESSESTHEPROGRAMMABLECONTROLLERHASBECOMEAPOWERFULTOOLFORFACTORYAUTOMATION,WIDELYPOPULARREPLICATIONPROGRAMMABLECONTROLLERISUSERORIENTEDINDUSTRIESDEDICATEDCONTROLCOMPUTER,WITHMANYDISTINCTIVEFEATURESFIRST,HIGHRELIABILITY,ANTIINTERFERENCECAPABILITY;SECOND,PROGRAMMINGVISUAL,SIMPLE;THIRD,ADAPTABILITYGOOD;FOURTHFUNCTIONALIMPROVEMENTS,STRONGFUNCTIONALINTERFACE2HISTORYOFPLCPROGRAMMABLELOGICCONTROLLERSPLC,ACOMPUTINGDEVICEINVENTEDBYRICHARDEMORLEYIN1968,HAVEBEENWIDELYUSEDININDUSTRYINCLUDINGMANUFACTURINGSYSTEMS,TRANSPORTATIONSYSTEMS,CHEMICALPROCESSFACILITIES,ANDMANYOTHERSATTHATTIME,THEPLCREPLACEDTHEHARDWIREDLOGICWITHSOFTWIREDLOGICORSOCALLEDRELAYLADDERLOGICRLL,APROGRAMMINGLANGUAGEVISUALLYRESEMBLINGTHEHARDWIREDLOGIC,ANDREDUCEDTHEREBYTHECONFIGURATIONTIMEFROM6MONTHSDOWNTO6DAYSMOODYANDMORLEY,1999ALTHOUGHPCBASEDCONTROLHASSTARTEDTOCOMEINTOPLACE,PLCBASEDCONTROLWILLREMAINTHETECHNIQUETOWHICHTHEMAJORITYOFINDUSTRIALAPPLICATIONSWILLADHEREDUETOITSHIGHERPERFORMANCE,LOWERPRICE,ANDSUPERIORRELIABILITYINHARSHENVIRONMENTSMOREOVER,ACCORDINGTOASTUDYONTHEPLCMARKETOFFROSTANDSULLIVAN1995,ANINCREASEOFTHEANNUALSALESVOLUMETO15MILLIONPLCSPERYEARWITHTHEHARDWAREVALUEOFMORETHAN8BILLIONUSDOLLARSHASBEENPREDICTED,THOUGHTHEPRICESOFCOMPUTINGHARDWAREISSTEADILYDROPPINGTHEINVENTOROFTHEPLC,RICHARDEMORLEY,FAIRLYCONSIDERSTHEPLCMARKETASA5BILLIONINDUSTRYATTHEPRESENTTIMETHOUGHPLCSAREWIDELYUSEDININDUSTRIALPRACTICE,THEPROGRAMMINGOFPLCBASEDCONTROLSYSTEMSISSTILLVERYMUCHRELYINGONTRIALANDERRORALIKESOFTWAREENGINEERING,PLCSOFTWAREDESIGNISFACINGTHESOFTWAREDILEMMAORCRISISINASIMILARWAYMORLEYHIMSELFEMPHASIZEDTHISASPECTMOSTFORCEFULLYBYINDICATINGIFHOUSESWEREBUILTLIKESOFTWAREPROJECTS,ASINGLEWOODPECKERCOULDDESTROYCIVILIZATIONPARTICULARLY,PRACTICALPROBLEMSINPLCPROGRAMMINGARETOELIMINATESOFTWAREBUGSANDTOREDUCETHEMAINTENANCECOSTSOFOLDLADDERLOGICPROGRAMSTHOUGHTHEHARDWARECOSTSOFPLCSAREDROPPINGCONTINUOUSLY,REDUCINGTHESCANTIMEOFTHELADDERLOGICISSTILLANISSUEININDUSTRYSOTHATLOWCOSTPLCSCANBEUSEDINGENERAL,THEPRODUCTIVITYINGENERATINGPLCISFARBEHINDCOMPAREDTOOTHERDOMAINS,FORINSTANCE,VLSIDESIGN,WHEREEFFICIENTCOMPUTERAIDEDDESIGNTOOLSAREINPRACTICEEXISTENTSOFTWAREENGINEERINGMETHODOLOGIESARENOTNECESSARILYAPPLICABLETOTHEPLCBASEDSOFTWAREDESIGNBECAUSEPLCPROGRAMMINGREQUIRESASIMULTANEOUSCONSIDERATIONOFHARDWAREANDSOFTWARETHESOFTWAREDESIGNBECOMES,THEREBY,MOREANDMORETHEMAJORCOSTDRIVERINMANYINDUSTRIALDESIGNPROJECTS,MORETHANOFTHEMANPOWERALLOCATEDFORTHECONTROLSYSTEMDESIGNANDINSTALLATIONISSCHEDULEDFORTESTINGANDDEBUGGINGPLCPROGRAMSINADDITION,CURRENTPLCBASEDCONTROLSYSTEMSARENOTPROPERLYDESIGNEDTOSUPPORTTHEGROWINGDEMANDFORFLEXIBILITYANDRECONFIGURABILITYOFMANUFACTURINGSYSTEMSAFURTHERPROBLEM,IMPELLINGTHENEEDFORASYSTEMATICDESIGNMETHODOLOGY,ISTHEINCREASINGSOFTWARECOMPLEXITYINLARGESCALEPROJECTSTHEOBJECTIVEOFTHISTHESISISTODEVELOPASYSTEMATICSOFTWAREDESIGNMETHODOLOGYFORPLCOPERATEDAUTOMATIONSYSTEMSTHEDESIGNMETHODOLOGYINVOLVESHIGHLEVELDESCRIPTIONBASEDONSTATETRANSITIONMODELSTHATTREATAUTOMATIONCONTROLSYSTEMSASDISCRETEEVENTSYSTEMS,ASTEPWISEDESIGNPROCESS,ANDSETOFDESIGNRULESPROVIDINGGUIDANCEANDMEASUREMENTSTOACHIEVEASUCCESSFULDESIGNTHETANGIBLEOUTCOMEOFTHISRESEARCHISTOFINDAWAYTOREDUCETHEUNCERTAINTYINMANAGINGTHECONTROLSOFTWAREDEVELOPMENTPROCESS,THATIS,REDUCINGPROGRAMMINGANDDEBUGGINGTIMEANDTHEIRVARIATION,INCREASINGFLEXIBILITYOFTHEAUTOMATIONSYSTEMS,ANDENABLINGSOFTWAREREUSABILITYTHROUGHMODULARITYTHEGOALISTOOVERCOMESHORTCOMINGSOFCURRENTPROGRAMMINGSTRATEGIESTHATAREBASEDONTHEEXPERIENCEOFTHEINDIVIDUALSOFTWAREDEVELOPER3NOWOFPLCFROMTHESTRUCTUREISDIVIDEDINTOFIXEDPLCANDMODULEPLC,THETWOKINDSOFPLCINCLUDINGCPUBOARD,I/OBOARD,DISPLAYPANEL,MEMORYBLOCK,POWER,THESEELEMENTSINTOADONOTREMOVEOVERALLMODULETYPEPLCINCLUDINGCPUMODULE,I/OMODULES,MEMORY,THEPOWERMODULES,BOTTOMORAFRAME,THESEMODULESCANBEACCORDINGTOCERTAINRULESCOMBINATIONCONFIGURATIONINTHEUSERVIEW,ADETAILEDANALYSISOFTHECPUSINTERNALUNNECESSARY,BUTWORKINGMECHANISMOFEVERYPARTOFTHECIRCUITTHECPUCONTROLWORKS,BYITREADSCPUINSTRUCTION,INTERPRETSTHEINSTRUCTIONANDEXECUTESINSTRUCTIONSBUTTHEPACEOFWORKBYSHOCKSIGNALCONTROLUNITWORKUNDERTHECONTROLLERCOMMANDUSEDINADIGITALORLOGICOPERATIONINCOMPUTINGANDSTORAGEREGISTEROFCOMPUTATIONRESULT,ITISALSOAMONGTHECONTROLLERCOMMANDANDWORKCPUSPEEDANDMEMORYCAPACITYISTHEIMPORTANTPARAMETERSFORPLC,ITSDETERMINESTHEPLCSPEEDOFWORK,IOPLCNUMBERANDSOFTWARECAPACITY,SOLIMITSTOCONTROLSIZECENTRALPROCESSINGUNITCPUISTHEBRAINOFAPLCCONTROLLERCPUITSELFISUSUALLYONEOFTHEMICROCONTROLLERSAFORETIMETHESEWERE8BITMICROCONTROLLERSSUCHAS8051,ANDNOWTHESEARE16AND32BITMICROCONTROLLERSUNSPOKENRULEISTHATYOU’LLFINDMOSTLYHITACHIANDFUJICUMICROCONTROLLERSINPLCCONTROLLERSBYJAPANESEMAKERS,SIEMENSINEUROPEANCONTROLLERS,ANDMOTOROLAMICROCONTROLLERSINAMERICANONESCPUALSOTAKESCAREOFCOMMUNICATION,INTERCONNECTEDNESSAMONGOTHERPARTSOFPLCCONTROLLERS,PROGRAMEXECUTION,MEMORYOPERATION,OVERSEEINGINPUTANDSETTINGUPOFANOUTPUTSYSTEMMEMORYTODAYMOSTLYIMPLEMENTEDINFLASHTECHNOLOGYISUSEDBYAPLCFORAPROCESSCONTROLSYSTEMASIDEFORMTHISOPERATINGSYSTEMITALSOCONTAINSAUSERPROGRAMTRANSLATEDFORMALADDERDIAGRAMTOABINARYFORMFLASHMEMORYCONTENTSCANBECHANGEDONLYINCASEWHEREUSERPROGRAMISBEINGCHANGEDPLCCONTROLLERSWEREUSEDEARLIERINSTEADOFPLASHMEMORYANDHAVEHADEPROMMEMORYINSTEADOFFLASHMEMORYWHICHHADTOBEERASEDWITHUVLAMPANDPROGRAMMEDONPROGRAMMERSWITHTHEUSEOFFLASHTECHNOLOGYTHISPROCESSWASGREATLYSHORTENEDREPROGRAMMINGAPROGRAMMEMORYISDONETHROUGHASERIALCABLEINAPROGRAMFORAPPLICATIONDEVELOPMENTUSERMEMORYISDIVIDEDINTOBLOCKSHAVINGSPECIALFUNCTIONSSOMEPARTSOFAMEMORYAREUSEDFORSTORINGINPUTANDOUTPUTSTATUSTHEREALSTATUSOFANINPUTISSTOREDEITHERAS“1”ORAS“0”INASPECIFICMEMORYBIT/EACHINPUTOROUTPUTHASONECORRESPONDINGBITINMEMORYOTHERPARTSOFMEMORYAREUSEDTOSTOREVARIABLECONTENTSFORVARIABLESUSEDINUSEDPROGRAMFOREXAMPLE,TIMEVALUE,ORCOUNTERVALUEWOULDBESTOREDINTHISPARTOFTHEMEMORYPLCCONTROLLERCANBEREPROGRAMMEDTHROUGHACOMPUTERUSUALWAY,BUTALSOTHROUGHMANUALPROGRAMMERSCONSOLESTHISPRACTICALLYMEANSTHATEACHPLCCONTROLLERCANPROGRAMMEDTHROUGHACOMPUTERIFYOUHAVETHESOFTWARENEEDEDFORPROGRAMMINGTODAY’STRANSMISSIONCOMPUTERSAREIDEALFORREPROGRAMMINGAPLCCONTROLLERINFACTORYITSELFTHISISOFGREATIMPORTANCETOINDUSTRYONCETHESYSTEMISCORRECTED,ITISALSOIMPORTANTTOREADTHERIGHTPROGRAMINTOAPLCAGAINITISALSOGOODTOCHECKFROMTIMETOTIMEWHETHERPROGRAMINAPLCHASNOTCHANGEDTHISHELPSTOAVOIDHAZARDOUSSITUATIONSINFACTORYROOMSSOMEAUTOMAKERSHAVEESTABLISHEDCOMMUNICATIONNETWORKSWHICHREGULARLYCHECKPROGRAMSINPLCCONTROLLERSTOENSUREEXECUTIONONLYOFGOODPROGRAMSALMOSTEVERYPROGRAMFORPROGRAMMINGAPLCCONTROLLERPOSSESSESVARIOUSUSEFULOPTIONSSUCHASFORCEDSWITCHINGONANDOFFOFTHESYSTEMINPUT/OUTPUTSI/OLINES,PROGRAMFOLLOWUPINREALTIMEASWELLASDOCUMENTINGADIAGRAMTHISDOCUMENTINGISNECESSARYTOUNDERSTANDANDDEFINEFAILURESANDMALFUNCTIONSPROGRAMMERCANADDREMARKS,NAMESOFINPUTOROUTPUTDEVICES,ANDCOMMENTSTHATCANBEUSEFULWHENFINDINGERRORS,ORWITHSYSTEMMAINTENANCEADDINGCOMMENTSANDREMARKSENABLESANYTECHNICIANANDNOTJUSTAPERSONWHODEVELOPEDTHESYSTEMTOUNDERSTANDALADDERDIAGRAMRIGHTAWAYCOMMENTSANDREMARKSCANEVENQUOTEPRECISELYPARTNUMBERSIFREPLACEMENTSWOULDBENEEDEDTHISWOULDSPEEDUPAREPAIROFANYPROBLEMSTHATCOMEUPDUETOBADPARTSTHEOLDWAYWASSUCHTHATAPERSONWHODEVELOPEDASYSTEMHADPROTECTIONONTHEPROGRAM,SONOBODYASIDEFROMTHISPERSONCOULDUNDERSTANDHOWITWASDONECORRECTLYDOCUMENTEDLADDERDIAGRAMALLOWSANYTECHNICIANTOUNDERSTANDTHOROUGHLYHOWSYSTEMFUNCTIONSELECTRICALSUPPLYISUSEDINBRINGINGELECTRICALENERGYTOCENTRALPROCESSINGUNITMOSTPLCCONTROLLERSWORKEITHERAT24VDCOR220VACONSOMEPLCCONTROLLERSYOU’LLFINDELECTRICALSUPPLYASASEPARATEMODULETHOSEAREUSUALLYBIGGERPLCCONTROLLERS,WHILESMALLANDMEDIUMSERIESALREADYCONTAINTHESUPPLYMODULEUSERHASTODETERMINEHOWMUCHCURRENTTOTAKEFROMI/OMODULETOENSURETHATELECTRICALSUPPLYPROVIDESAPPROPRIATEAMOUNTOFCURRENTDIFFERENTTYPESOFMODULESUSEDIFFERENTAMOUNTSOFELECTRICALCURRENTTHISELECTRICALSUPPLYISUSUALLYNOTUSEDTOSTARTEXTERNALINPUTOROUTPUTUSERHASTOPROVIDESEPARATESUPPLIESINSTARTINGPLCCONTROLLERINPUTSBECAUSETHENYOUCANENSURESOCALLED“PURE”SUPPLYFORTHEPLCCONTROLLERWITHPURESUPPLYWEMEANSUPPLYWHEREINDUSTRIALENVIRONMENTCANNOTAFFECTITDAMAGINGLYSOMEOFTHESMALLERPLCCONTROLLERSSUPPLYTHEIRINPUTSWITHVOLTAGEFROMASMALLSUPPLYSOURCEALREADYINCORPORATEDINTOAPLC4PLCDESIGNCRITERIAASYSTEMATICAPPROACHTODESIGNINGPLCSOFTWARECANOVERCOMEDEFICIENCIESINTHETRADITIONALWAYOFPROGRAMMINGMANUFACTURINGCONTROLSYSTEMS,ANDCANHAVEWIDERAMIFICATIONSINSEVERALINDUSTRIALAPPLICATIONSAUTOMATIONCONTROLSYSTEMSAREMODELEDBYFORMALLANGUAGESOR,EQUIVALENTLY,BYSTATEMACHINESFORMALREPRESENTATIONSPROVID

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