机电 自动化控制类 英文文献.docx
《机电 自动化控制类 英文文献.docx》由会员分享,可在线阅读,更多相关《机电 自动化控制类 英文文献.docx(11页珍藏版)》请在冰豆网上搜索。
机电自动化控制类英文文献
TheoreticalComputerScience253(2001)61{93
DevelopingaHybridProgrammableLogicControllerPlatformforaFlexibleManufacturingSystem
HenningDierks1
UniversityofOldenburg,FachbereichInformatik,Postfach2503,2900Oldenburg,Germany
Abstract:
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.Introduction
Inavarietyofproductmanufacturingindustries,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.DescriptionoftheFMS
SIhandlingconveyorsystem
Thisconsistsoffourcarts,A,B,C,andD,withfixturesmountedoneach,twotransfertables,TT1andTT2,anddualconveyorswhichtransportmaterialstoeachworkstation.
Figure1.Flexiblemanufacturingsystem.
NASAIICNCmillingmachine
Themillingmachineacceptsrectangularsolidblanksandmachineseachpartofdifferenttypesaccordingtoitscomputercontroller.
GEP50robot
AsharedrobotisusedtoloadandunloadthematerialbetweentheCNCmillingmachineandtheconveyorsystem,andbetweenthepartspresentationstationandconveyorsystem.ItcontainsfivecomputerprogramsassignablebythePLC.ThecomputerprogramsdirecttherobottoloadthematerialbetweenthepartspresentationstationandthecartsandbetweentheCNCmachineandthecarts.Thelasttwoprogramsplacethecompletedpartsintheacceptorrejectarea.
Partspresentationstation
Thisstationincludesagravity-chute,whichsuppliesrectangularsolidblanksasrawmaterials.Thisstationalsocontainstwobintypes,oneeachforacceptedpartsandrejectedparts.
Computervisionsystem
Thevisionsystemprovidesforthevisualautomatedinspectionoftheparts.Itisamenu-driven,64-levelgrayscale,edgedetectionsystem.
Drillingmachine
AnIBM7535industrialrobotwithanautomateddrillasanend-effectordrillsvariousholesinthepartsasdirected.
Insummary,theFMShastworobots,oneCNCmill,amaterialtransferconveyorsystemincludingtransportationcartsandpositioninglimitswitches,andavisionsystem,whicharesupervisedbyaGE-SeriesSixPLCandmonitoredbyaPC-basedvisualMMI/DAS.
3.Operationaldescription
TheworkingcycleforthisFMSproceedsinthefollowingmanner:
1.Initially,allfourcartsontheconveyorsystemareemptyandavailablefortherawmaterialstobeloadedontothemfromthepartspresentationstation.
2.TheGErobotloadsfourparts,onebyone,ontothefourcartsontheconveyorsystem.Thecartsmoveclockwiseastheyarebeingloaded.
3.Figure2showsthepositionsacquiredbythefourcartsoncethefourpartsofdifferenttypeshavebeenloaded.
4.TheIBMrobotdrillsvariousholesoneachblankpartasthecartstopsatthedrillingmachine.
5.TheGErobotmovestotheconveyor,removesthepartfromthecartatpositionX1,andloadsitintothefixturelocatedontheCNCmachinetable.
6.OncethepartisloadedontheCNCmillingmachine,therobotretracts,andthemillingmachinemillstherectangularpartasrequired.
7.Afterthemillingoperation,therobotarmmovestothemillingmachinetoremovethepartthatwasmachinedfromtheholdingfixture.
Figure2.Loadingstateoftheconveyorsystem.
8.Therobotreturnsthefinishedparttothesamecartontheconveyor.
9.Asignalissenttothevisioncameratoinspectthepart.
10.Thevisionsystemanalyzesthepartandoutputsasignalthatdirectstherobottoacceptorrejectthepart.
11.Therobotrunseitheranacceptprogramtoplacethepartintheacceptbinorrunsarejectprogramtoplacethepartintherejectbin.
12.TheGErobotgoestothepartspresentationstationandloadsanewblankpartintothecart.
13.Thecartisreleasedtothesystemandthenextcycleisstarted.
4.ControlofanFMSwithaPLC
ThesignificantfeaturesoftheFMScontrolsystemareasfollows:
1.Thesystemiseasytoconfigureandtomodifytoaccommodatechangesandupdates,becauseoftheladderlogiccapabilityofthesystem.
2.Inasimilarmanner,thesystemiseasytoprogramanddocument.
3.Thesystemcanbeeasilymaintained,andtroubleshootingisdecreasedbecauseon-linediagnosticsareprovidedtopinpointproblemsanddecreasemaintenance.
4.Naturally,thesystemisreadilyinterfacedwiththecomputer.
ThePLCisageneralpurposeindustrialcomputerwhichiswidelyusedinindustrialprocesscontrol.Itiscapableofstoringinstructionstoimplementcontrolfunctionssuchassequencing,timing,counting,arithmetic,datamanipulation,andcommunicationtocontrolindustrialmachinesandprocesses.ThePLCischosentoperformanFMScontroltaskbasedonthefollowingfeatures:
1)goodreliability;
2)lessspacerequiredandoperatesinanindustrialenvironment;
3)easiertomaintainbyplantengineerortechnician;
4)canbereprogrammedifcontrolrequirementschange;
5)cancommunicateandnetworkwithothercomputers.
Inthisapplication,aGE-SeriesSixPLCisequippedwithamemorybank,andtheI/Oracksareloadedwiththefollowinginputandoutputinterfaces:
120VACinputmoduleswith8ports/module,24VDCinputmoduleswith8ports/module,and120VACoutputmoduleswith8ports/module.
5.PC-basedvisualoperatorinterfaceunit
Withtheconvergenceofmicroprocessortechnologyandsoftwaretechniques,thePChasbecomeveryusefulinoperatorinterfaceapplications.PCsrunningMMI/DASfront-endsmakepowerful,intuitiveoperationinterfaces,fullofusefulgraphicsandreportingtools.InformationfromthesePCscanbedistributedthroughacompany’slocalare