建筑电气英文论文.docx

建筑电气英文论文.docx

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建筑电气英文论文

ARCHITECTURALANDCOLLABORATIVECONTROLSYSTEMSACOMPLEMENTARYSYMBIOSIS

-Lookingattoday’scontrolsystemonecanfindawidevarietyofimplementations.Frompurearchitecturaltocollaborativecontrolsystem（CCS）toolkitstohomegrownsystemsandanyvariationin-between.DecisionsonthetypeofimplementationshouldbedrivenbytechnicalargumentsRealityshowsthatfinancialandsociologicalreasonsformthecompletepicture.Anydecisionhasit’sadvantagesandit’sdrawbacks.Reliability,gooddocumentationandsupportareargumentsforindustrialcontrols.Financialargumentsdrivedecisionstowardscollaborativetools.Keepingthehandsonthesourcecodeandbeingabletosolveproblemsonyourownandfasterthanindustryaretheargumentforhomegrownsolutionsoropensourcesolutions.Theexperienceofmanyyearsofoperationsshowsthatwhichsolutionistheprimaryonedoesnotmatter,therearealwaysareaswhereatleastpartoftheotherimplementationsexist.Asaresultheterogeneoussystemshavetobemaintained.Thesupportfordifferentprotocolsisessential.Thispaperdescribesourexperiencewithindustrialcontrolsystems,PLCcontrolledturnkeysystems,theCCStoolkitEPICSandtheoperabilitybetweenallofthem.

-INTRODUCTION

ProcesscontrolsingeneralstartedatDESYintheearly80thwiththeinstallationofthecryogeniccontrolsystemfortheacceleratorHERA（Hadron-Elektron-Ring-Anlage）.Anewtechnologywasnecessarybecausetheexistinghardwarewasnotcapabletohandlestandardprocesscontrolssignalslike4to20mAinputandoutputsignalsandthesoftwarewasnotdesignedtorunPIDcontrolloopsatastablerepetitionrateof0.1seconds.Inadditionsequenceprogramswerenecessarytoimplementstartupandshutdownproceduresforthecomplexcryogenicprocesseslikecoldboxesandcompetecompressorstreets.

Soonitwasnecessarytoaddinterfacestofieldbusesandtoaddcomputingpowertocryogeniccontrols.SincetheinstalledD/3system[1]onlyprovidedandocumentedserialconnectiononamultibusboard,thedecisionwasmadetoimplementaDMAconnectiontoVMEandtoemulatethemultibusboard’sfunctionality.ThenecessarycomputingpowerfortemperatureconversionscamefromaMotorolaMVME167CPUandthefieldbusadaptertotheinhouseSEDACfieldbuswasrunningonanadditionalMVME162.TheoperatingsystemwasVxWorksandtheapplicationwastheEPICStoolkit.

SincethisimplementationwassuccessfulitwasalsoimplementedfortheutilitycontrolswhichwerelookingforagenericsolutiontosupervisetheirdistributedPLC’s.

ASELECTIONOFPROCESSCONTROLSYSTEMSATDESY

DCS（D/3）

AsaresultofamarketsurveytheD/3systemfromGSEwasselectedfortheHERAcryogenicplant.ThedecisionwasfortunatebecauseoftheDCScharacteroftheD/3.Thepossibilitytoexpandthesystemonthedisplay-andontheI/OsidehelpedtosolvetheincreasingcontroldemandsforHERA.ThelimitingfactorforthesizeofthesystemisnotthetotalnumberofI/Obutthetrafficonthecommunicationnetwork.Thistrafficisdeterminedbythetotalamountofarchiveddatanotbythedataconfiguredinthealarmsystem.Thetechnicalbackgroundofthislimitationisthefactthatarchiveddataarepolledfromthedisplayserverswhereasthealarmsarepushedtoconfigureddestinationslikealarm-files,（printer）queuesordisplays.

SCADASystemswithDCSFeatures（Cube）

ThefactthattheD/3systemmentionedabovehadsomehardcodedlimitationswithrespecttotheY2Kproblemwasforcingustolookforanupgradeorareplacementoftheexistingsystem.AsaresultofacallfortenderthecompanyOrsiwiththeirproductCubecameintoplay[2].Theprojectincludedacompletereplacementoftheinstalledfunctionality.ThisincludedtheD/3aswellastheintegrationoftheDESYfieldbusSEDACandthetemperatureconversioninVME.Theprojectstartedpromising.Butsoontechnicalandorganizationalproblemswerepushingthescheduletoit’slimitswhichweredeterminedbytheHERAshutdownscheduledatthattime.Thefinalacceptancetestatthevendorssiteshoweddramaticperformanceproblems.Twofactorscouldbeidentifiedasthecauseoftheseproblems.ThefirstonewasrelatedtotheunderestimatedCPUloadofthe6thgradepolynomialtemperatureconversionrunningat1Hz.ThesecondonewastheadditionalCPUloadcausedbythecomplexfunctionalityoftheexistingD/3system.Hereitwasunderestimatedthateachdigitalandanaloginputandoutputchannelhadit’sownalarmlimitsintheD/3system.InaSCADAlikesystemasCubethebasefunctionalityofachannelistoreadthevalueandmakeitavailabletothesystem.Anyadditionalfunctionalitymustbeadded.Lastnotleasttheloadonthenetworkforpollingallthealarmlimits–typicallyforaSCADAsystem–wasalsodrivingthenetworktoit’slimits.

FinallythecontractwithOrsiwascancelledandanupgradeoftheD/3systemwastheonlypossiblesolution.Itwasfinallycarriedoutinmarch2003.

InanycaseitshouldbementionedthattheCubeapproachhadtheadvantageofahomogeneousconfigurationenvironment（fortheCubefrontendcontrollers）–comparedwithheterogeneousenvironmentsfor‘pure’SCADAsystems.

SCADA（PVSS-II）

TheH1experimentattheHERAacceleratordecidedtousePVSS-IIforanupgradeoftheirslowcontrolsystems[3].TheexistingsystemsweredevelopedbyseveralmembersoftheH1collaborationandweredifficulttomaintain.ThedecisiontousePVSSasareplacementwasdrivenbytheresultsofanextensivesurveycarriedoutatCERNbytheJointControlsProject[4].PVSSisa‘pure’SupervisoryAndDataAcquisitionSystem（SCADA）.ItprovidesasetofdriversforseveralfieldbusesandgenericsocketlibrariestoimplementcommunicationoverTCP/IP.Thecoreelementisthesocalledeventmanager.Itcollectsthedata（mostlybypolling）fromtheI/Odevicesandprovidesaneventservicetotheattachedmanagementserviceslike:

controlmanager,databasemanager,userinterface,APImanagerandthebuiltinHTTPserver.ThePVSSscriptinglibraryallowstoimplementcomplexsequencesaswellascomplexgraphics.ComparedwithotherSCADAsystemsPVSScomeswithonebasicfeature:

itprovidesatrueobjectorientedAPItothedevice’sdata.

OnemajordisadvantageofSCADAsystemsisthefactthattwodatabases,theoneforthePLCandtheonefortheSCADAsystemmustbemaintained.Integratedenvironmentstrytoovercomethisrestriction.

EPICS

EPICShasemergedatDESYfromaproblemsolvertoafullyintegratedcontrolsystem.Startingfromthedatacollectorandnumbercruncherforthecryogeniccontrolsystem,EPICSmadeit’swaytobecomethecoreapplicationfortheDESYutilitygroup.InadditionitisusedwhereverdataisavailablethroughVMEboardsorbymeansofIndustryPack（IP）modules.ForthosecryogenicsystemswhicharenotcontrolledbytheD/3systemEPICSisusedwithit’scompletefunctionality.Intotalabout50InputOutputController（IOC）areoperationalprocessingabout25thousandrecords.

1EPICSasaSCADASystem

Theutilitygroup（water,electricalpower,compressedair,heatingandairconditioning）isusingavarietyofPLC’sspreadoutoverthewholeDESYsite.EPICSisusedtocollectthedatafromthesePLC’soverProfibus（FMSandDP）andoverEthernet（SiemensH1andTCP）.TheIOC’sprovidetheinterfacestothebusesandcollectthedata.ThebuiltinalarmcheckingoftheEPICSrecordsisusedtostoreandforwardalarmstatestothealarmhandler（alh）oftheEPICStoolkit.Inadditiontoolslikethechannelarchiverandthegraphicdisplay（dm2k）areused.Thedefaultnameresolution（byUDPbroadcast）andthedirectoryserver（nameserver）areusedtoconnect

clientandserverapplicationsoverTCP.AllofthesearebasicallySCADAfunctions.

Thetextualrepresentationofallconfigurationfiles（fortheIOC,thegraphictool,thealarmhandlerandthearchiver）providesaflexibleconfigurationscheme.AtDESYtheutilitygrouphasdevelopedasetoftoolstocreateIOCdatabasesandalarmconfigurationfilesfromOracle.ThiswaythecontrolsgroupprovidestheservicetomaintaintheEPICStoolsandtheIOC’swhiletheuserscanconcentrateontheequipmentbeingcontrolled.

2EPICSasaDCSSystem

BesidesthebasiccomponentsofaSCADAsystemEPICSalsoprovidesafullflavouredInputOutputController（IOC）.TheIOCprovidesallofthefunctionaDCSsystemrequires,suchas:

astandardsetofpropertiesimplementedineachrecord,builtinalarmcheckingprocessedduringtheexecutionofeachrecord;controlrecordslikePIDetc.;configurationtoolsfortheprocessingengine.TheflexiblenamingschemeandthedefaultdisplayandalarmpropertiesforeachrecordeasetheconnectionbetweentheoperatortoolsandtheIOC’s.Theflexibledataacquisitionsupportsthepollmodeaswellasthepublishsubscribemode.Thelatterreducesthetrafficdrastically.

PLC’s

PLC’sprovidenowadaysthesamerichfunctionalityasitwasknownfromstandalonecontrolsystemsinthepast.BesidesthebasicfeaturesliketheperiodicexecutionofadefinedsetoffunctionstheyalsoallowextensivecommunicationoverEthernetincludingembeddedhttpserversanddifferentsetsofcommunicationprograms.Besidesthecommunicationprocessors,displayprocessorscanbelinkedtoPLC’stoprovidelocaldisplayswhichcanbecomprisedastouchpanelsforoperatorinterventionandvaluesettings.

ThesekindofPLC’sareattractiveforturnkeysystemswhicharecommissionedatthevendorssiteandlaterintegratedintothecustomerscontrolsystem.

IntelligentI/O

NewdevelopmentsinI/Odevicesallowto‘cluster’I/Oinevensmallergroupsand