自動(dòng)控制理論概述英語(yǔ)

ThedevelopmentandapplicationofPLC

Abstract:

ThefullnameofPLCisprogrammablecontroller,itisdefinedasadigitalcomputingoperationsoftheelectronicsystem,specificallydesignedforapplicationinindustrialenvironments.It’smainstructurebypowersupply,thecentralprocessingunit,memory,inputandoutputinterfacecircuit,functionmodules,andcommunicationmodules.becauseofPLChasstrongcommonality,useconvenient,wideadaptability,easytoprogrammandothercharacteristics,it’susedwidelyinthemilitary,thenationaldefense,aerospace,transportationandindustrialproduction.Thereforeitcannotbereplacedintheforeseeablefuture.Asweknow,PLChasmanyschools,PLCdevelopinginChinaisveryquickly,especiallyintheapplication.

Keyword:

Developmentprocess,controlfunction,application,trend

Summary:

TheProgrammableLogicController(PLC),itusesaProgrammablememoryforitsinternalstorageprocedures,toperformtheLogicoperation,sequencecontrol,timing,countingandarithmeticoperation。andthroughthedigitaloranaloginput/outputtocontrolvarioustypesofmachineryorproductionprocessintheindustrialautomationcontrolfield.PLChastheimportantpositionintheindustryandhasanirreplaceableroleinthefuture.

Fromnowon,theworld'sbestPLCproductionismainlycontainedGermany'sSiemens,Japan'sMitsubishi,HoneywellcompanyinUSA,PLCisdividedintowholetypeandmoduletypeaccordingtothestructure.accordingtotheapplicationenvironmentintoon-siteinstallationandcontrolroominstallation;what’smore,aCPUwordlengthcanbedividedinto4,8,16,32,64bites.Fromtheapplicationpointofview,itusuallycanbechooseincontrolledfunctionorinputandoutputpoints.

Inthisrespect,PLCcontrolfunctionsalsousedinmanyindustrialfields,anditsfuturedevelopmentiscloselyrelatedtotheindustrialdevelopment.

PLCthedevelopmenthistoryandmainschools

Intheindustrialproductionprocess,alargenumberofswitchordercontrol,orderofactioninaccordancewithlogicalconditions,andcontrollingthemotionofchainprotection,andalargenumberofdiscretedataacquisitioninaccordancewiththelogicalrelationship.Traditionally,thesefunctionsareachievedbypneumaticorelectricalcontrolsystems.U.S.GM(GeneralMotors)proposedtoreplacethefollowingelectricalcontroldevicerequirementsin1968,thesecondyear,theU.S.Digitaldevelopedatechnology-basedintegratedcircuitsandelectroniccontroldevices,it’sthefirsttimeusedinelectricalcontrol,Thisisthefirstgenerationofprogrammablelogiccontroller,calledtheProgrammableController(PC).Inordertofacilitatethedevelopmentofthepersonalcomputer(referredtoasPC)toreflectthefeaturesoftheprogrammablecontroller,whichtobecalledtheProgrammableLogicController(PLC),andnow,thePLCsometimesreferredtothePC.

PLCcontrolfunctions

Firsttheoperationfunction

Simplearithmeticfunctionsoftheprogrammablelogiccontrollerincludinglogicoperations,timingandcountingfunctions;commonprogrammablelogiccontrolleroperationfeaturesalsoincludetheshiftdatatocomparethecomputingcapabilities;morecomplexcalculationfunctionalgebra,anddatatransfer;large-scaleprogrammablelogiccontrollerandanalogPIDoperationandotheradvancedcomputingcapabilities.Withtheadventofopensystems,programmablelogiccontrollerhaveacommunicationfunction,someproductswiththesamemachineorthehostcomputercommunication,someproductswiththefactoryorenterprisenetworkfordatacommunicationsfunctions.Sodesignselectionshouldbefromtherequirementsofpracticalapplication,therationaluseofcomputingcapabilitiesisrequired.Mostapplicationsonlyneedthelogicoperationandtimingcount,someapplicationsrequiredatatransmissionand,whenusedinanalogdetectionandcontrol,tousealgebra,numericalconversionandPIDoperation.Todisplaythedatarequiredfordecodingandencodingoperations.

Secondthecontrolfunction

Off-lineprogrammingmethod:programmablelogiccontrollerandprogrammerpublicaCPU,aprogrammingconsoleinprogrammingmodel,CPUforaprogrammingconsoleprovidestheservice,nottheequipmentcontrol.Completeprogramming,aprogrammingconsoleswitchtothemodeofoperation,totheCPUcontrolequipment,notforprogramming.Off-lineprogrammingmethodscanreducethesystemcost,buttouseanddebuggingnotconvenient.Theonlineprogrammingway:theCPUandaprogrammingconsolehavetheirownCPU,thehostCPUresponsibleforon-sitecontrol,andinascanningcycleandprogrammerfordataexchange,programmeroftheonlineprogramsordatasenttothehost,thenextscanningcycle,accordingtothenewhostsreceivedprogramsrunning.Thiswaycostishigher,butsystemcommissioningandconvenientoperation,inlargeandmedium-sizedprogrammablelogiccontrolleroftenused.

Thirdcommunicationfunction

WiththefunctionofPLCnetworkcommunication,itmakesthePLCandPLC,betweenthePLCandthePCandotherintelligencetoexchangeinformationbetweendevices,formaunifiedwhole,scatteredrealizecentralcontrol.MostofthePLChaveRS-232interface,andsomebuilt-insupporttheircommunicationprotocolinterfaces.

Programmablelogiccontrollersystemofcommunicationnetworkisthemainformofthefollowingseveralkindsofforms:

1),PC-basedstation,multipleprogrammablelogiccontrollerofthesamemodelfromthestation,composedofsimpleprogrammablelogiccontrollernetwork;

2),aprogrammablelogiccontroller-basedstation,programmablelogiccontrollerofthesamemodelastheslaveconstitutesamaster-slaveprogrammablelogiccontrollernetwork;

3),programmablelogiccontrollernetworkthroughaspecificnetworkinterfacetoconnecttolargeDCSDCSsubnet;

4),adedicatedprogrammablelogiccontrollernetwork(manufacturersdedicatedprogrammablelogiccontrollercommunicationsnetwork).

Fourthprogrammingfunction

Fivestandardizedprogramminglanguage:sequencediagram(SFC),functionladderdiagram(LD),functionmodulechart(FBD)threegraphicallanguageandstatementtable(IL),structuretext(ST)twotextlanguage.Theselectionofprogramminglanguageshouldabidebyitsstandards(IEC6113123),meanwhile,stillshouldsupportavarietyofprogramminglanguageforms,suchasC,Basicetc,inordertomeetthespecialcontrolthecontrolrequirementsoftheoccasion.

Fifthdiagnosisfunction

Programmablelogiccontrollerdiagnosisfunctionincludingthehardwareandsoftwareofthediagnosis.Hardwarediagnosisthroughthehardwarelogictodeterminethefaultlocationhardware,softwareandthediagnosistheirfairshareofthediagnosisdiagnosis.ThroughthesoftwaretointernalperformanceandPLCfunctionwithinthediagnosisisadiagnosis,throughthesoftwareofprogrammablelogiccontrollersCPUandexternalinput/outputcomponentsuchasinformationexchangefunctionthediagnosisisadiagnosis.

Sixthprocessingspeed

Programmablelogiccontrollerusingscanningmode.Real-timedemandfromview,processingspeedshouldbethesoonerthebetter,ifthesignallasttimelessthanscanningtime,theprogrammablelogiccontrollerwillscanlessthanthissignal,causingsignallossofdata.

Processingspeedandtheuserprogramlength,theCPUprocessingspeed,andsoftwarequalityandsoon.Atpresent,theprogrammablelogiccontrollerofthecontactsfastresponse,highspeed,allthebinaryinstructiontimeabout0.2~0.4Ls,andtherefore,canadapttothecontrolrequirementishigh,thecorrespondingrequirementfastapplications.Scanningperiod(processorscanningcycle)shouldmeet:smallprogrammablelogiccontrollerscanningtimenotmorethan0.5ms/K;Largeandmedium-sizedprogrammablelogiccontrollerscanningtimenotmorethan0.2ms/K.

**thedevelopmenttrendofindustrialprogrammablelogiccontroller(plc)

plcautomationsystemelectroniccontroldeviceasoneoftheIPCinthemajorindustrialcountriesiseasytocontrol,highreliability,easytograsp,smallsize,andaffordable.Accordingtostatistics,plcmanufactureroftheworldtodayisabout150,producingover300varieties.2000annualsalesofapproximately$8.6billion,accountingfor50%ofIPC'smarketshare,plc,playsanessentialroleintheIPCmarket,andmaintainthemomentumcontinuestorise.

plc,whenintroducedintoChinainthelate1960s,usedonlyfordiscretecontrol,itsfunctionistooperatethecontactorreceiveddiscreteoutput,onlytheearliestcompletionoftheoperationofrelayladderlogic.Thenewgenerationplcpidregulatoryfunction,anditsapplicationfromtheswitchcontrolextendedtothefieldofanalogcontrol,widelyusedinaerospace,metallurgy,lightindustry,buildingmaterialsandotherindustries.PLCasindustrialPC,andamemberofthemajorindustrialcountriesinbecomeautomationsystemofbasicelectronicdevice.Ithasconvenientcontrol,highreliabilityandeasytomaster,smallvolume,pricesforetc.Characteristics.Accordingtothestatistics,themodernworldPLCmanufacturerabout150home,producingmorethan300varieties.In2000,salesofaroundus$8.6billion,accountingfor50%ofthemarketshareofindustrialcomputer,PLCwillbeinthemajorityofindustrialPCmarket,andkeeprisingtrend.

thePLCintheindustrialanddomestic

PLCintheindustry,whichiswidelyusedinthemanufacturingsectorarealsoappreciated.PLCisoneofthethreepillarsofthemodernindustrialautomationandcontrol,thethreepillarsarePLC,CAD,androbotics.Itworkswhentheprogrammablelogiccontrollerwasputintooperation,thecourseoftheirworkisgenerallydividedintothreestages,namely,theinputsample,theuserprogramexecutionandoutputrefreshthreestages.Completionofthethreestagesiscalledascancycle.Duringtheentireoperation,theCPUoftheprogrammablelogiccontrollerscanspeed,repeattheabovethreestages.PLCcyclescanisdifferentfromthemostimportantfeatureofcomputerandothercontrolequipment.InthelifeofseveralcommonPLCapplicationatypicalcase:acrossroadsoftrafficlights,automaticcontrolsystemofgreenhouse,elevator,automaticcontrolandsoon.Arealsomanyapplicationsinindustry,suchasmultiplewindturbines,pumpaut