崔开,plc英文文献翻译

TheoreticalComputerScience253(2001)61{93:Inthisarticle,wepresentthedesignandimplementationofaflexiblemanufacturingsystem(FMS)controlplatformbasedonaprogrammablelogiccontroller(PLC)andapersonalcomputer(PC)-basedvisualman-machineinterface(MMI)anddataacquisition(DAS)unit.ThekeyaspectofanFMSisitsflexibilitytoadapttochangesinademandingprocessoperation.ThePLCprovidesfeasiblesolutionstoFMSapplications,usingPC-basedMMI/DAS,wherebyPLCsareoptimizedforexecutingrapidsequentialcontrolstrategies.PCsrunningMMI/DASfront-endsmakeintuitiveoperationinterfaces,fullofpowerfulgraphicsandreportingtools.InformationfromthePCcanbedistributedthroughacompany’slocalareanetworkorwebusingclient-servertechnologies.Currently,withtheconvergenceofunderlyingmicroprocessortechnologyandsoftwareprogram-mingtechniques,manyusersfindthatPLCsprovideacost-effectivesolutiontoreal-timecontrolinsmall-tomedium-sizedprocessplants,especiallywhencombinedwithsupervisoryPCsusinghybridsystems.ThemajorworkofthisarticledemonstratesthatPLCsareresponsivetorapidandrepetitiouscontroltasks,usingPCsthatpresenttheflowofinformationautomationandacceptoperatorinstructions,therebyprovidingtheuseratooltomodifyandmonitortheprocessastherequirementschange.KeyWords:PLC、FMS、PC.1．IntroductionInavarietyofproductmanufacturingindustries,themostautomatedformofproductionisaFlexiblemanufacturingsystem(FMS),firstintroducedin1970s.SincetheFMSscanprovideahighpotentialforproductivityimprovementinbatchmanufacturing,thenumberofFMSsisgrowingsubstantially(GrooverandZimmers,1984).Theaccelerationthroughouttheworldisduetoincreasedglobalcompetition,reducedmanufacturingcycletimes,andcutsinproductioncosts.Generally,anFMSconsistsofagroupofmachinesorotherautomatedworkstations,whichformintomodularsubsystems,suchasCNCmachines,robots,visionsystems,andaprocessstation.Theseareinterconnectedbyamaterialshandlingsystemandusuallydrivenbyacomputer(Maleki,1991).Eachmodularsystemrequiresanindividualmodularcontrolsystem,withdifferentcomponentsbeingcontrolledbyindividualcontrollerunits.Allofthemodularsubsystemsarecontrolledbycomputersasusual.Thesecontrollersperformtheirintendedtasksundersupervisionofahigherlevelcontroller.Tothesystem,boththecontroldevicesaswellastheflowofinformationneedtobeautomated.ThekeyaspectofanFMSisitsabilitytoadapttochangesinthecontroltasks.Thisflexibilityincludesthequantitiesandvarietiesofparttypeswhichitcanproduce,theorderinwhichoperationsmaybeperformed,anditsabilitytoreroutepartsbackintoflowpaths.Intheend,thecontrolplatformshouldhavethecapabilitytoautomatetheflowofinformation.Typically,therearethreetypesofcontrolplatformsusedinFMSs:minicomputers,microcomputers,andPLCs(Maleki,1991).Theminicomputersarebestsuitedforcomplexlarge-scale,continuous,regulatorycontrolapplications.ThePLCsareusedforrapidandrepetitiouslogiccontrol.Personalcomputers(PCs)aresuitedforoperatorinterfacefunctions.Primarily,PLCsaredesignedtoreplacehardwiringrelays,tooperateinanindustrialenvironment,tobeeasilymodifiedbyplantengineersandmaintenancepersonnel,andtobemaintainedbyplantelectricians.Currently,withtheconvergenceofunderlyingmicroprocessortechnologyandsoftwareprogramming,manyusersfindthatPLCsprovideacost-effectivesolutiontoreal-timecontrolinsmall-tomedium-sizedprocessplants,especiallywhencombinedwithsupervisoryPCsusinghybridsystems.Thepurposeofthisarticleistoaddressthestate-of-the-arttechnologyofFMSs.ThedesignandconstructionofanFMSusingPLC-controlledandPC-basedvisualman-machineinterface(MMI)anddataacquisitionsystem(DAS)arepresented.Itisorganizedasfollows.Section2beginswiththedescriptionoftheFMSonthefactoryflooroftheCenterforManufacturingSystemsattheNewJerseyInstituteofTechnology(NJIT).Section3showstheoperationaldescriptionoftheFMS.Sections4and5presenttheapplicationsofPLC-controlledandPC-basedMMI/DASfortheFMSatNJIT.Section6containsasummaryoftheadvantagesofthisPLC-controlledandPC-basedMMI/DASforFMSapplication.2.DescriptionoftheFMSSIhandlingconveyorsystemThisconsistsoffourcarts,A,B,C,andD,withfixturesmountedoneach,twotransfertables,TT1andTT2,anddualconveyorswhichtransportmaterialstoeachworkstation.Figure1.Flexiblemanufacturingsystem.NASAIICNCmillingmachineThemillingmachineacceptsrectangularsolidblanksandmachineseachpartofdifferenttypesaccordingtoitscomputercontroller.GEP50robotAsharedrobotisusedtoloadandunloadthematerialbetweentheCNCmillingmachineandtheconveyorsystem,andbetweenthepartspresentationstationandconveyorsystem.ItcontainsfivecomputerprogramsassignablebythePLC.ThecomputerprogramsdirecttherobottoloadthematerialbetweenthepartspresentationstationandthecartsandbetweentheCNCmachineandthecarts.Thelasttwoprogramsplacethecompletedpartsintheacceptorrejectarea.PartspresentationstationThisstationincludesagravity-chute,whichsuppliesrectangularsolidblanksasrawmaterials.Thisstationalsocontainstwobintypes,oneeachforaccept