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

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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