机电自动化控制类英文文献.docx
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机电自动化控制类英文文献.docx
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机电自动化控制类英文文献
TheoreticalComputerScience253(2001)61{93
www。
elsevier。
com/locate/tcs
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'slocalarea
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