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