工业控制系统自动化中英文翻译大学本科方案设计书

工业控制系统和协同控制系统INDUSTRIALANDCOLLABORATIVECONTROLSYSTEMSACOMPLEMENTARYSYMBIOSIS-Lookingattoday?scontrolsystemonecanfindawidevarietyofimplementations.Frompureindustrialtocollaborativecontrolsystem(CCS)toolkitstohomegrownsystemsandanyvariationin-between.DecisionsonthetypeofimplementationshouldbedrivenbytechnicalargumentsRealityshowsthatfinancialandsociologicalreasonsformthecompletepicture.Anydecisionhasit?sadvantagesandit?sdrawbacks.Reliability,gooddocumentationandsupportareargumentsforindustrialcontrols.Financialargumentsdrivedecisionstowardscollaborativetools.Keepingthehandsonthesourcecodeandbeingabletosolveproblemsonyourownandfasterthanindustryaretheargumentforhomegrownsolutionsoropensourcesolutions.Theexperieneeofmanyyearsofoperationsshowsthatwhichsolutionistheprimaryonedoesnotmatter,therearealwaysareaswhereatleastpartoftheotherimplementationsexist.Asaresultheterogeneoussystemshavetobemaintained.Thesupportfordifferentprotocolsisessential.Thispaperdescribesourexperiencewithindustrialcontrolsystems,PLCcontrolledturnkeysystems,theCCStoolkitEPICSandtheoperabilitybetweenallofthem.INTRODUCTIONthProcesscontrolsingeneralstartedatDESYintheearly80withtheinstallationofthecryogeniccontrolsystemfortheacceleratorHERA(Hadron-Elektron-Ring-Anlage).Anewtechnologywasnecessarybecausetheexistinghardwarewasnotcapabletohandlestandardprocesscontrolssignalslike4to20mAinputandoutputsignalsandthesoftwarewasnotdesignedtorunPIDcontrolloopsatastablerepetitionrateof0.1seconds.Inadditionsequenceprogramswerenecessarytoimplementstartupandshutdownproceduresforthecomplexcryogenicprocesseslikecoldboxesandcompetecompressorstreets.Soonitwasnecessarytoaddinterfacestofieldbusesandtoaddcomputingpowertocryogeniccontrols.SincetheinstalledD/3system[1]onlyprovidedandocumentedserialconnectiononamultibusboard,thedecisionwasmadetoimplementaDMAconnectiontoVMEandtoemulatethemultibusboard?sfunctionality.ThenecessarycomputingpowerfortemperatureconversionscamefromaMotorolaMVME167CPUandthefieldbusadaptertotheinhouseSEDACfieldbuswasrunningonanadditionalMVME162.TheoperatingsystemwasVxWorksandtheapplicationwastheEPICStoolkit.SincethisimplementationwassuccessfulitwasalsoimplementedfortheutilitycontrolswhichwerelookingforagenericsolutiontosupervisetheirdistributedPLC?s.ASELECTIONOFPROCESSCONTROLSYSTEMSATDESYDCS(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.Thefinalacceptaneetestatthevendorssiteshoweddramaticperformaneeproblems.Twofactorscouldbeidentifiedasthecauseoftheseproblems.ThefirstonewasrelatedtotheunderestimatedCPUloadofthe6gradepolynomialtemperatureconversionrunningat1Hz.ThesecondonewastheadditionalCPUloadcausedbythecomplexfunctionalityoftheexistingD/3system.Hereitwasunderestimatedthateachdigitalandanaloginputandoutputchannelhadit?sownalarmlimitsintheD/3system.InaSCADAlikesystemasCubethebasefunctionalityofachannelistoreadthevalueandmakeitavailabletothesystem.Anyadditionalfunctionalitymustbeadded.Lastnotleasttheloadonthenetworkforpollingallthealarmlimits—typicallyforaSCADAsystem-wasalsodrivingthenetworktoit?slimits.FinallythecontractwithOrsiwascancelledandanupgradeoftheD/3systemwastheonlypossiblesolution.Itwasfinallycarriedoutinmarch2003.InanycaseitshouldbementionedthattheCubeapproachhadtheadvantageofahomogeneousconfigurationenvironment(fortheCubefrontendcontrollers)-comparedwithheterogeneousenvironmentsfor,pure?SCDAsystems.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.EPICSEPICShasemergedatDESYfromaproblemsolvertoafullyintegratedcontrolsystem.Startingfromthedatacollectorandnumbercruncherforthecryogeniccontrolsystem,EPICSmadeit?swaytobecomethecoreapplicationfortheDESYutilitygroup.InadditionitisusedwhereverdataisavailablethroughVMEboardsorbymeansofIndustryPack(IP)modules.ForthosecryogenicsystemswhicharenotcontrolledbytheD/3systemEPICSisusedwithit?scompletefunctionality.Intotalabout50InputOutputController(IOC)areoperationalprocessingabout25thousandrecords.EPICSasaSCADASystemTheutilitygroup(water,electricalpower,compressedair,heatingandairconditioning)isusingavarietyofPLC?sspreadoutoverthewholeDESYsite.EPICSisusedtocollectthedatafromthesePLC?soverProfibus(FMSandDP)andoverEthernet(SiemensH1andTCP).TheIOC?sprovidetheinterfacestothebusesandcollectthedata.ThebuiltinalarmcheckingoftheEPICSrecordsisusedtostoreandforwardalarmstatestothealarmhandler(alh)oftheEPICStoolkit.Inadditiontoolslikethechannelarchiverandthegraphicdisplay(dm2k)areused.Thedefaultnameresolution(byUDPbroadcast)andthedirectoryserver(nameserver)areusedtoconnectclientandserverapplicationsoverTCP.AllofthesearebasicallySCADAfunctions.Thetextualrepresentationofallconfigurationfiles(fortheIOC,thegraphictool,thealarmhandlerandthearchiver)providesaflexibleconfigurationscheme.AtDESYtheutilitygrouphasdevelopedasetoftoolstocreateIOCdatabasesandalarmconfigurationfilesfromOracle.ThiswaythecontrolsgroupprovidestheservicetomaintaintheEPICStoolsandtheIOC?swhiletheuserscanccentrateontheequipmentbeingcontrolled.EPICSasaDCSSystemBesidesthebasiccomponentsofaSCADAsystemEPICSalsoprovidesafullflavouredInputOutputController(IOC).TheIOCprovidesallofthefunctionaDCSsystemrequires,suchas:astandardsetofpropertiesimplementedineachrecord,builtinalarmcheckingprocessedduringtheexecutionofeachrecord;controlrecordslikePIDetc.;configurationtoolsfortheprocessingengine.TheflexiblenamingschemeandthedefaultdisplayandalarmpropertiesforeachrecordeasetheconnectionbetweentheoperatortoolsandtheIOC?s.Theflexibledataacquisitionsupportsthepollmodeaswellasthepublishsubscribemode.Thelatterreducesthetrafficdrastically.PLC?sPLC?sprovidenowadaysthesamerichfunctionalityasitwasknownfromstandalonecontrolsystemsinthepast.BesidesthebasicfeaturesliketheperiodicexecutionofadefinedsetoffunctionstheyalsoallowextensivecommunicationoverEthernetincludingembeddedhttpserversanddifferentsetsofcommunicationprograms.Besidesthecommunicationprocessors,displayprocessorscanbelinkedtoPLC?stoprovidelocaldisplayswhichcanbecomprisedastouchpanelsforoperatorinterventionandvaluesettings.ThesekindofPLC?sareattractiveforturnkeysystemswhicharecommissionedatthevendorssiteandlaterintegratedintothecustomerscontrolsystem.IntelligentI/ONewdevelopmentsinI/Odevicesallowto,cluster?I/OinevensmallergroupsandconnectthesesclusteredI/Ochannelsdirectlytothecontrolsystem.PLC?sarenotanymorenecessaryfordistributedI/O.SimplecommunicationprocessorsforanykindoffieldbusesorforEthernetallowaneasyintegrationintotheexistingcontrolsinfrastructure.LittlelocalenginescanrunIEC61131programs.ThedifferencesbetweenPLC?sandintelligentI/Osubsystemsfadeaway.FUNCTIONALITYTheeverlastingquestionwhycontrolsystemsforacceleratorsandotherhighlyspecializedequipmentareoftenhomegrownoratleastdevelopedinacollaborationbutonlyinrarecasescommercialshallnotbeansweredhere.Wetrytosummarizeherebasicfunctionalitiesofdifferentcontrolsapproaches.Front-endControllerOneofthecoreelementsofacontrolsystemisthefront-endcontroller.PLC?scanbeusedtoimplementmostofthefunctionstocontroltheequipment.Thedisadvantageisthecomplicatedaccesstothecontrolsproperties.ForinstaneeallofthepropertiesofacontrolloopliketheP,IandDparameter,butalsothealarmlimitsandotheradditionalpropertiesmustbeaddressedindividuallyinordertoidentifytheminthecommunicationprotocolandlastnotleastinthedisplay-,alarm-andarchiveprograms.InadditionanykindofmodificationsoftheseembeddedpropertiesisdifficulttotrackbecausetwoormoresystemsareinvoIved.ThismightbeonestrongargumentwhycontrolloopsaremainlyimplementedontheIOClevelratherthanPLC?s.I/OandControlLoopsComplexcontrolalgorithmsandcontrolloopsarethedomainofDCSalikecontrolsystems.Thesupportforsetsofpredefineddisplayandcontrolspropertiesisessential.Ifnotalreadyavailable(likeinDCSsystems)suchsetsofgenericpropertiesaretypicallyspecifiedthroughoutacompletecontrolsystem(seenamespaces).Sequenee/StateprogramsSequeneeprogramscanrunonanyprocessorinacontrolsystem.Theruntimeenvironmentdependsontherelevaneeofthecodeforthecontrolsystem.Programsfulfillingwatchdogfunctionshavetorunonthefront-endprocessordirectly.Sequeneeprogramsforcomplicatedstartupandshutdownprocedurescouldberunonaworkstationaswell.ThebasicfunctionalityofastatemachinecanbeevenimplementedinIEC61131.Codegeneratorscanproduce,C?codewhichcanbecompiledfortheruntimeenvironment.SupportedHardwareThesupportforfieldbusesandEthernetbasedI/OisabasicfunctionalityforSCADAtypesystemsitiscommerciallyavailablefromanySCADAsystemonthemarket.Theintegrationofspecifichardwarewithspecificdriversanddataconversionisthehardpartinacommercialenvironment.OpenAPI?sorscriptingsupportsometimeshelptointegratecustomhardware.Ifthesetoolsarenotprovidedforthecontrolsystemitisdifficult-ifnotimpossible-tointegratecustomhardware.NewindustrialstandardslikeOPCallowthecommunicationwithOPCawaredevicesandthecommunicationbetweencontrolsystems.Oneboundaryconditionforthiskindoffunctionalityistheunderlyingoperatingsystem.InthecaseofOPCitisboundtoDCOMwhichisaMicrosoftstandard.UNIXbasedcontrolsystemshaveahardtimetogetconnected.Onlycontrolsystemssupportingmultipleplatformscanplayamajorroleinaheterogeneousenvironments.Asaresultthelimitedsupportforcustom-orspecializedhardwaremaygivereasonforthedevelopmentofanewcontrolsystem.DisplayandOperationBesidesthefront-endsystemtheoperatorinterfacesplayamajorrolefortheacceptanceofacontrolsystem.SCADAtoolscomewithahomogeneouslookandfeelthroughouttheirsetoftools.Toolkitsimplementedinacollaborationmightvarybecausetheindividualtoolsweredevelopedbydifferentteams.GraphicSynopticdisplaysaretheadvertisingsignforanycontrolsystem.Commercialsynopticdisplayscomewitharichfunctionalityandlotsofspecialfeatures.Startingtomakeuseofallthesefeaturesonewillfindoutthatallindividualpropertiesofthegraphicobjectsmustbespecifiedindividually.SineeSCADAsystemsmustbegenerictheycannotforeseethataninputchanneldoesnotonlyconsistofavaluebutalsoconsistsofpropertieslikedisplayrangesandalarmvalues.Definingallofthesepropertiesagainandagaincanbeaprettyboringjob.Somesystemsallowtogenerateprototypesofgraphicobjects.Theseprototypeortemplategraphicsarecomplexandneedaspecialisttogeneratethem.DCSorcustomsynopticdisplayprogramscanmakeuseofthecommonsetofpropertieseachI/Opointprovides.Thispredefinednamingschemewillfillinallstandardpropertyvaluesandthusonlyrequiretoentertherecord-ordevicenameintotheconfigurationtool.AclearadvantageforcontrolsystemswithanotionofI/OobjectsratherthanI/Opoints.AlarmingAlarmsaregoodcandidatestodistinguishbetweendifferentcontrolsystemarchitectures.ThosesystemswhichhaveI/Oobjectimplementedalsoprovidealarmcheckingonthefront-endcomputer.ThosesystemswhichonlyknowaboutI/OpointshavetoaddalarmcheckingintotheI/Oprocessing.WhiletheI/OobjectapproachallowstoimplementalarmcheckinginthenativeprogrammingIanguageofthefront-endsystem,I/OpointorientedsystemstypicallyhavetoimplementthisfunctionalityintheirnativescriptingIanguage.Thisistypicallylessefficientanderrorpronebecauseallpropertiesmustbeindividuallyconfigured.Thisleadstoafloodofproperties.NotonlytheerrorstatesforeachI/OpointwinduptobeindividualI/OpointsbutalsothealarmlimitsandthealarmseverityofeachlimitmustbedefinedasI/Opointsifitisdesiredtobeabletochangetheirvaluesduringruntime.BesidesthisimpactontheconfigurationsidetheprocessingandforwardingofalarmsmakesthediffereneebetweenSCADAandDCSsystems.SinceSCADAsystemsinherentlydonot,know?aboutalarms,eachalarmstatemustbepolledeitherdirectlyfromtheclientapplicationorinadvaneedcasesfromaneventmanagerwhichwillforwardalarmstatestotheclients.Inanycasealotofoverheadfor,just?checkingalarmlimits.DCSsystemagainhavetheadvantagethatclientscaneitherregisterthemselvesforalarmstatesundthusgettheinformationforwardedorareconfiguredtosendalarmchangestocertaindestinationsspreadaroundthecontrolsystem.Thelattercaseisonlypossibleforsystemswhichintotalareconfiguredwithallthenodestakingpartinthecontrolsnetwork.TrendingandArchivingTrendinghasbecomeanimportantbusinessincontrolsystemsarchitectures.Trendsarenecessarytotraceerrorconditionsorforpostmortemandperformaneeanalysisofthecontrolledplant.Besidessomecustomimplementationswhicharecapabletostorethedataofcompletecontrolobjects,mostofthetrendingtoolsarchivescalardata.Additionalfeatureslikeconditionaltrendingorcorrelationplotsmakeupthediffereneebetweenindividualimplementations.ProgrammingInterfacesWithrespecttoopenprogramminginterfacesPLC?sandDCSsystemshaveacommonstrategy.Theyarerunningreliablybecausethere?snowaytointegratecustomcodewhichcouldinterferewiththeinternalprocessing.Asaconsequeneethecustomerhastoorder‘specials?whichareextremelyexpensive-orforgetaboutitandusethesystemasablackbox.SineeSCADAsystemsbydefinitionmustbeabletocommunicatewithavarietyofI/OsubsystemstheyalreadyhavesomebuiltinAPI?swhichallowtointegratecustomfunctionality.Speciallycollaborativesystemsneedacertainopennesstofulfillalltherequirementsfromvariousdevelopmentgroups.Programminginterfacesonalllevelslikefont-endI/O,front-endprocessing,networkingetc.aremandatory.Aclearadvantageforthistypeofsystem.RedundancyIfredundancymeanstheseamlessswitchwhichtakesoverallthestatesandallthevaluesoftheI/Oandallstatesofallprogramscurrentlyrunning,itisadomainofonlyafewDCSsystems.CustomorCCSimplementationdonotprovidethiskindoffunctionality.Maybebecauseoftheimmenseeffortandthefactthatitisonlyrequiredinrarecases.Besidesprocessorredundancy,redundantnetworksorI/OsubsystemsareavailableforcertaincommercialDCSsystems.Again-adomainwhichisnotcoveredbySCADAorCCSimplementations.AdvaneedsafetyrequirementsmaybecoveredbyredundantPLCsubsystems.Theseareforinstaneeinstalledin(nuclear)powerplants.RequirementsforPersonalProtectionSystems(PPS)cansometimesonlybefulfilledbyredundantPLC?s.InprocesseontrolsredundantPLC?sareonlyusedinrarecases.NamespaceTheflatnamespaceofSCADAsystemshasalreadybeendescribedinthealarmsection.SomeSCADAsystems(likePVSS-II)providethenotionofeontrolobjectsorstructureddatawhichisararecase.Inallothercasessocalledfieldobjectsmustbespecified.Theseareobjectswhicheonsistofalistofproperties(implementedasI/Opoints)andasetofmethods(implementedasmacrosorfunctioncalls).OneoftheseapproachesistheUniNifiedIndustrialCOntrolSystem(UNICOS)atCERN[5].DCSsystemsandmostofthecustom/collaborativesystemsarerecord-ordeviceoriented.ThediffereneebeingthattypicallyonerecordisconnectedtoasingleI/Opointandprovidesthiswayallsubfeaturesofarecordimplementationlikeindividualengineeringunits,display-andalarmlimits.ThedeviceorientedapproachallowstoconnectseveralI/Opoints.Themajordiffereneebeingthefactthatanobjectorienteddeviceimplementationprovidesmethodsandstatesforadevicewhile(EPICS)recordsonlyserveacertainsetofbuiltinfunctions.Naminghierarchiesarenotspecifictoatypeofimplementation.Theyareavailableforsomesystemsofanykind.Forsurehierarchicalnamingschemesaredesirable.IMPLEMENTATIONSTRATEGIESAfterhavingshownallthepossiblecontrolsapproachesitistimetohavealookattheimplementationofcontrolsystems.StartingfromtheI/Olevelonehastodecidewhethercommercialsolutionarerequired,feasibleorwanted.SpecialI/Odoesnotalwaysrequirecustomsolutionforthefont-endcontroller.Signalscanbeconvertedintostandardsignalsbutthisdoesnotapplyforallkindsofsignals.Resolution,repetitionratesandsignallevelsmightrequirecustomdevelopmentswhichmustbeintegratedintotheoverallcontrolarchitecture.EvenifthesignalscannotbeconnectedtostandardI/OinterfacesitmightbepossibletodevelopI/Ocontrollerswhichimplementafieldbusinterfacewhichallowtheintegrationwithcommercialcontrolsystems.Oncethislevelofintegrationisnotpossiblecustomfront-endcontrollerslikeVMEcratescomeintoplay.BesidesthedecisionwhetherspecialI/Orequiresdedicatedcustomsolutionsonehastodecidewhowilldowhichpartofthework?DoesforinstaneethenecessityofVMEcratesprohibitthedeliveryofa,turnkey?systembuiltbyindustry?OrdoesaPLCbasedfront-endsystemrequireacommercialSCADAsystemforhighlevelcontrols?TurnKeySystemsItisacleartrendinindustrytodeliverturnkeysystems.Itallowsamodulardesignofthewholesystem.Individualcomponentscanbesubcontractedtoseveralcompaniesandtestedlocally.Oncedeliveredtotheconstructionsitetheprimaryacceptaneetestshavealreadybeenpassedandthesecondphase,tointegratethesubsystemintotheglobalcontrolsystembegins.Whilethedetailedspecificationofcontrolloopsetc.isnowpartofthesubsystemscontract,thecustomerhastospecifyclearlyhowmuchinformationofthesubsystemmustbemadeavailable,whatthedatastructureswilllooklikeandwhichconnection(fieldbus/Ethernet)willbeused.MostturnkeysystemsaredeliveredwithPLC?s.TieconstructionoftheSwissLightSource(SLS)hasshownthatalsoaVMEbasedI/OsystemrunningaCCS-inthiscaseEPICS-canbesuccessfullycommissioned[6].PLCBasedSystemsPLCbasedsystemsareaconsequeneeoftheturnkeyansatz.ThenextobviousapproachmightbetolookbesidescommercialPLC?salsoforcommercialSCADAsystems.TheadvantageisclearlythesamelikeforthePLC:stablesoftware,noprogramming—onlyconfiguration,supportandgooddocumentation.AtDESYwehavesuccessfullyestablishedarelationbetweenthecontrolsgroupwhichprovidesaCCSservicebasedonEPICSandtheutilitygroupwhichusestheEPICSconfigurationtoolstosetuptheircontrolenvironment.ThebigadvantagethoughbeingthattheEPICScodecanbeadjustedtothespecialrequirementsfrombothsides.IndustrialSolutionsThediffere