Programmable logic controller.docx
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Programmable logic controller.docx
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Programmablelogiccontroller
Programmablelogiccontroller
Theearlymachinesweremadeupofcams,gears,levers,andsomeotherbasicmechanicalequipment.Withtheincreasingcomplexityofthemachine,alsoneedamorecomplexcontrolsystemtocontroltheconnectionfunctionmodulesofthissystemincludesthecontrolswitchandrelay,thesemodulesaccordingtotheneedsofsomelogicfunctionsandsomespecifictypesofmachineoperationgroupareconnectedintoawhole,whichisnotaneedtochangethehardwarebutwiththeimprovementofproductiontechnologycanbeeasilyportedtonewproducts,withthemajorityofequipmentupgradescaneasilycontrolmachines,changecircuitswitchingandswitchinglogicisverycumbersomeandtimeconsuming,fortheproductionofanewcircuittochangethecontrolschemeandreconnectisinevitable,modifyitverythedifficultiesanddesignuptospendalotoftime,somesmallproblemsintheprocessofinstallingthedesignwillbecometheleadlineSystemsneedtoberedesignedforkeyfactorsmustberemodifythecontrolcircuit,theAmericanautoindustryleadthedevelopmentandpromotionofthenewtechnology,becamealeadingfigureintheindustryasawhole,thisnewtechnologyinthelate1960sandearly1970sobtainedvigorousdevelopment,fromthebirthprogrammingcontroller,alsoknownasPLC,automobilemanufacturingindustryfacingmanufacturingprocessofall-roundimprovement,suchasimprovementsinsomeaspectsmustbelinkedtootheraspects,PLCprovidesasimplemethodbyreprogramminginsteadofthelineofthewholesystemasawholechange.
IntheprogramdevelopmentduringthedevelopmentofthePLCsystemisnotaneasything,forthedesignofPLCprogramminglanguageisaverytroublesomething,thisworkrequiresanexperiencedprogrammerandtrainedwithregularitytocomplete,earlydevicefunctionsonlybyfrequentchangeofrelaytoachievePLC,PLCnowgradually,therapiddevelopmentinrecentyearshasbecomeacomplexandhighlyversatilecontrolsystemcomponents,eachmodulehastheabilitytoperformcomplexmathematicalfunctionsincludingintegralanddifferentialoperation,thesefunctionsarethroughafastmicroprocessor,oldPLCdiscreteinputandoutput(i.e.switchinputsignal)today,thesystemcanreceiveandgenerateanalogvoltageandcurrent,widelevelandpulsesignal,thePLCdesignprocessisverydifficult,Unlikeintheexistingcomputertechnologybasedonthedesignofthenewcomputercaneasilywithstandtheexternalenvironmentsuchasvibration,shock,temperaturerise,andtheinterferenceofelectromagneticnoise.
Withmoreandmoremanufacturersinvolvedinthecompany'sproductionanddevelopment,PLCfunctionexpandrapidly,programminglanguagealsogreatrich,thisisthedevelopmentofeverynewthingmustgothroughtheprocess,alsovariousmanufacturerstendtodeveloptheirownladderlogiclanguage(foraPLCprogramminglanguage).ThiscomplexPLClanguagecannotapplicabletoalltypesofequipment.However,withtheothercomputerlanguageslike,oncethisladderlanguagehasbeenwidelyused,thenthelanguagebeingusedinmostoftheequipmentonthepossibilityisbig,mostofthesystemdesignerswillfindproductionofaparticularmanufacturerofproductsforthewritingsystem.
Itshouldbenotedthattheprogrammablelogiccontrollerisoftenreferredtoas"PLC"or"programmablecontroller".Althoughtheterm"programmablelogiccontroller"hasbeenwidelyaccepted,itisnotliketheabbreviation"personalcomputer",becausetheabbreviation"personalcomputer"usuallyreferstothepersonalcomputerused.InthisarticlewewillseethatPLCdoesnotmeanpersonalcomputer.
Canbeprogrammablecontrolleristhepersonalcomputerusersasfreemanyconfigurationoptions,aspersonalcomputersselectedwhichisbettersomecompletelyrelyontheirownexperience,asacontrollerofalotofsetupoptionstogoodcontrolitmadehimworkneedstorelyontheirownexperience.。
ModularPLCincludingthesystemcomponentsare:
1processor
Processor(sometimesreferredtoasCPU)isaprogramofthecentralprocessorcanexecute,whichisfullofthemodulewithanumberofspecificfeatures,thesefeaturessomeprocessingmorecomplexmathematicaloperationsandsomeofthePIDcontrolloopandprogrammablecommandprocessoriscomposedofamicroprocessor,asystemmemory,serialcommunicationportandprinter,PLCLANlinksandexternalprogrammingequipmentsystemthroughtheI/Oportsupply.
2Architecture
Generally,themetalframeandtheprintedcircuitboardareconnectedwiththePLCinputandoutputmoduleandtheprocessor,andthenumberofthemountingframesrequiredforthesystemisrealizedaccordingtothespecifiedmodule.Theassemblyframeprovidesdataandpowerthroughthemotherboardandthemoduleconnectionprocessor.Withoutpowersupplystructuretopreservethemodularpowersupply,theprocessorofthesystemisindependentlyinstalledandthecablerackareconnectedtogether,frameassemblycanismounteddirectlytothepanel,orcanbeinstalledinthestandardwidthof19andmultiplemountingframebetweenislinkedtoensurethatadapttothelargenumberofI/Omoduleinthewholesystem.
3inputandoutputmodules
Theinputandoutput(I/O)modulesareconnectedtoaparticularapplicationprogrambasedonthespecifiedinputandoutputsignals,whichcanbedividedintodiscretecategories,analoghigh-speedcountersorregistertypes.
DiscreteI/Omodulesaregenerallyableto8-bitor16bitdataprocessing,insomecases,switchinputandoutputmoduleisspecifiedasaninputoroutput,butmanufacturersgenerallyprovideafreeallocationofinputsandoutputscanbecuredwithinthesamemodule.
Analoginputandoutputmoduleisfeasibleandapplicabletotheexpectedresolutionandvoltageorcurrentrange,thesehavebecomethegeneraldiscreteinputoroutputmodule,somemanufacturersbetweenthesamemoduleprovidesanaloginputandoutput,tosimulatethePLCcanalsobeaccepteddirectlythermocoupletemperaturemeasurementandmonitoring.
PulseinputtoPLCcanbeacceptedusinghighspeedcountermodule.Thismodulecanbeusedtomeasurethefrequencyoftheinputsignalfromthetachometerorfrequencygenerator.Thesemodulescanalsocounttheincomingpulsesifrequired.Ingeneral,boththefrequencyandcountofthesamemodule,ifbotharerequiredintheapplication.
Theregisterinputandoutputmodulestransmitinformationfrom16or8bits,andfromaprogrammablecontroller.Thesewordsareusuallynumbers(BCDcodeorbinary)whicharetheinputdatafromtheencoderswitchorencodersystemtobegeneratedbythePLCoutputdisplaydevice
4,powersupply
Thespecifiedpowerdependsonthemanufacturer'sprogrammablecontrollerusedintheapplication.Asmentionedabove,insomecases,thepowersupplytoprovidetherequiredpowerofthesystemasapartoftheprocessormodule.Ifthepowersupplyisaseparatemodule,itmustbeabletoprovideagreatercapacitythanthesumofallthecurrentsneededfortheothermodules.Fortheinternalprocessormoduleofpowersupplysystem,mayhavesomemodules,inthesystem,muchpower,ratherthanfromtheprocessor,becausevoltageorcurrentrequirements,onlythroughtheadditionofapowersupply.Thisisgenerallytrueiftheanalogorexternalcommunicationmodule,astheserequirementsoftheDCpowersupply,inthecaseoftheanalogmodule,mustbewellregulated.
5,programmingunit
Theprogrammingunitallowstheengineerortechnicalpersonneltoenterandedittheprogramexecution.Initssimplestform,itcanbeahandhelddevicethatshowsthestepsorfunctionsoftheinputanddisplaydevices(lightemittingdiodesorliquidcrystaldisplays)tothekeyboardinputprogram,asshowninfig..Moreadvancedsystemsuseasinglepersonalcomputer,whichallowsprogrammerstowrite,view,edit,anddownloadtheprogramintoaprogrammablecontroller.Thisisachievedbythemanufacturerwithproprietarysoftwareavailablefromtheprogrammablecontroller.Thesoftwarealsoallowstheprogrammerorengineertomonitortheprogramasitisrunningtheprogram.Withthismonitoringsystem,suchasinternalcoils,registers,timersandotheritemsthatarenotvisibleexternallycanbemonitoredtodeterminethecorrectoperation.Inaddition,theinternalregisterdatacanbechanged,ifrequiredtofinetunetheprogramoperation.Thismaybeadvantageouswhendebuggingaprogram.Communicationwiththesystem'sprogrammablecontrollerisacableconnectedtoaparticularprogrammingportonthecontroller.Connectedtopersonalcomputerscanbeinstalledthroughaserialportorfromaspecialcard.
Programmablecontrollerisakindofspecialcomputer.Becauseitisacomputer,ithasallthebasiccomponentsofacomputer,acentralprocessingunit,memory,inputinterfaceandoutputinterface.Thecentralprocessingunit(CPU)isanimportantpartofprogrammablelogiccontroller(PLC)control.Itcanexplainthesameproceduresandcommandsdirectlyfrommemoryandbehaviortothosecommands.Thisunitinthecurrentprogrammablelogiccontroller(PLC)isamicroprocessorbasedsystem.Processormoduleofcentralprocessingunit(CPU)insystemmodule.
Memorysystemsareusuallyoftwotypes,read-onlymemoryandrandomaccessmemory.ROM'smemorycontainsprograminformationthatallowsthecentralprocessortointerpretandactontheladderlogicprogramstoredintheRAMstore.RAMstorageisusuallyremovedinordernottolosethepoweroftheladderprogrammingsystem.Thebatterycanbeastandardtypeofdrybatterycharge.Nowtheprogrammablecontroller(PLC)unitwithelectricallyprogrammable
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