外文翻译-基于PLC的监测和控制平台的开发

英文原文DevelopmentofamonitoringandcontrolplatformforPLC-basedapplicationsAbstractThispaperdiscussesthedesignandimplementationofaplatformtoremotelymonitorandcontrolPLC-basedprocessesoverTCP/IPorbyusingtheGSMnetwork.Theplatformisbuiltusingindustry-standardoff-the-shelfPLCS.IntegratedwitheachPLCarecommunicationprocessorsthatcanbeusedforconnectivitytothenetworkandtoaGSMmodem.Thecommunicationprocessormodule(Ethernetmodule)usedinthiswork,providesanindustrialcompatibleprotocoloverTCP/IPthatachievesthesamefunctionalityasProfinetbutatamuchhigherbandwidth(10/100Mbps).Additionally,amobile-basedcommunicationprotocolthatfacilitatesremotemonitoringandcontrolofPLCsusingSMSmessageshasalsobeendeveloped.Theintenthereistoprovidesystemuserswithaback-upcommunicationmechanismincaseofanetworkfailure.2007ElsevierB.V.Allrightsreserved.Keywords:PLC;TCP/IP;GSM;Remotemonitoring1.IntroductionTherecentgrowthofnetworkstechnologyandspeciallythewidespreadoftheInternethavepromotedthedevelopmentofdistributedmeasurementsystemsforavarietyofindustrialapplications.Thesedistributedmeasurementsystemscanbeusedinthemonitoringandcontrolofvariousinstrumentsinthenetwork1,2.AProgrammableLogicController(PLC)ismicroprocessorbasedcontrolsystemthatcanbeprogrammedtosense,activateandcontrolindustrialequipmentandthereforeincorporatesanumberofinput/outputterminalsforinterfacingtoanindustrialprocess.AcontrolprogramstoredinthePLCmemorydeterminestherelationshipbetweentheinputsandoutputsofthePLC.PLCsareintelligentautomationstationsthatpossesshighlyusefulanddesirablefeaturessuchas3:Robustness.Highdegreeofscalability:modernPLCfamilieshaveawidespectrumofCPUtypesthatallowseasyscalabilityinfunctionalityandperformance.Extensibility:themodulardesignofPLCsenablestheextensionwithawiderangeofdigitalandanalogI/Omodules.Also,variousintegratedtechnologymodulesareavailableforvariousapplicationareas.Sophisticatedcommunicationcapabilities:modernPLCshavecommunicationportsthatprovideforcentralizedordistributedconnectivity.Powerfuldevelopmentenvironment:modernPLCfamiliescomewithacrossdevelopmentenvironmentthatsupportdifferentlanguagesforprogrammability,allowssemigraphicalhardwareconfigurationandofferstrongdebuggingmechanisms.Remoteaccesstocontrolandmonitorvariousdevicesinanindustrialsettingisofvaluetoengineersandautomationfacilities.CurrentimplementationsofremotePLCmonitorandcontrolusededicatedPCsorwebserversconnectedtothePLC.Fig.1illustratesacommonarchitectureusedinindustry.Asshown,PLCSareconnectedtothenetworkthroughacomputer.ThePLCSystemisusuallyinterfacedtothiscomputerusingtheserialPortorProfibus.ThesetypesofsystemsaredisadvantagedbythededicateduseofaPCtoaccessthePLCsystem.Thearchitecturealsodoesnotmakeuseoftheadventsandstridesmadeinareassuchastelecommunicationsandwebtechnology.AComputerStandards&Interfaces30(2008)157166/locate/csiCorrespondingauthor.E-mailaddress:(A.Sagahyroon).0920-5489/$-seefrontmatter2007ElsevierB.V.Allrightsreserved.doi:10.1016/j.csi.2007.08.008InrecentyearsandduetotheeverincreasingcapabilitiesofPCcomputingandtheinfluxofnetworkprotocolsandstandards,therehasbeenasurgeinthedesignandimplementationofdistributedmeasurementandcontrolsystemsforindustrialapplications.Typically,thesesystemsarebasedontheclientserverarchitecturewhilesecuringcommunicationusingtheTCP/IPprotocol46.ModernPLCscomewithembeddedwebserversthatprovideopenaccesstousefulrealtimeinformationanddiagnosticsthatcanbeviewedviaanystandardwebbrowser.Thisremoteaccessibilityprovidesseveraladvantagesovermoretraditionalsolutions.Forexample,aproblemcaneasilybediagnosedandperhapsfixedremotely;alsoengineerscanhaveremoteaccesstothePLCCPUconfigurationtoolsandhenceallowingforremoteupload/downloadandconfigurabilityviatheintranetorinternet.InthispaperwewilldiscussthedesignandimplementationofanetworkedplatformforremotemonitoringandcontrolofPLCs.TheplatformisbuiltaroundtheSiemensS7seriesofPLCs.ThesePLCshaveanintegratedcommunicationprocessorthatcanbeusedtoprovideaccessibilitytotheinternet.Themonitoringandcontrolcanbeaccomplishedinawiredorwirelessenvironment,viaanintranetorinternethenceprovidingforacompletesolutionfortheremotemonitoringandcontrolofindustrialprocesses.WewillalsodiscusstheutilizationoftheGSMnetworkandtheoperationofacommunicationprotocolthatusesSMSmessagingtocommunicatewiththePLCstationsandaDatabaseServerintegratedwiththesystem.Thepaperisorganizedasfollows:inSection2wedescribetheoverallsystemarchitecture;sectionthreeincludesadiscussionofthesoftwareaspectsofthesystem.Sections4and5presentthecommunicationsmethodologyfollowedinthisprojectandthepaperisconcludedinSection6.2.SystemarchitectureTheproposedsystemarchitectureisillustratedinFig.2.Thesystemconsistsofthefollowingcomponents:SomaticS7200/300PLCsystemsandCommunicationProcessors(CPs).EachCPhasanintegratedcommunicationinterface(hardwareandsoftware)thatallowsthePLCtocommunicateinaLAN,WANorviaaGSMnetwork.Clientsandadministratorareconnectedtotheprocessviathenetwork(orwirelessly).Privilegescanbesetorresetbyadministratorstoallowforortolimitthevariousclientsoptions.ADatabaseServerconnectedtotheprocessviathenetworkfordataloggingandeventrecording.AvarietyofnetworkoptionsincludingGSM-basedaccessibility.ThePLCsystemEthernetmoduleisacommunicationprocessorfortheS7familyusedtoconnectthePLCtothenetwork.AnadditionalcommunicationprocessorisusedtoallowcommunicationbetweenthePLCandtheGSMmodemovertheserialport(RS232).Intheproposedimplementation,thePLCsystemreportsremotelythestatusoftheprocesstotheDatabaseServer.TheDatabaseServerrecordsthestatusofthePLCintime-basedtablesandperformsanyrequireddataanalysis.ThesystemalsoreceivesandexecutescommandsfromadministratorsandclientstoFig.1.PC-basedremoteaccessibility.158S.Danaetal./ComputerStandards&Interfaces30(2008)157166controltheprocess.GSMconnectivityisalsoimplementedtoallowuserswithdifferentprivilegestoaccessthestatusofthemandatoryfunctionsofthePLCandallowthemtocontrolthesefunctions.EthernetandGSMconnectivityofthePLCsisimplementedusingtheCP343,andtheCP340communicationprocessors7.Fig.2.Systemarchitecture.Fig.3.Systemsoftwarecomponents.S.Danaetal./ComputerStandards&Interfaces30(2008)157166159.TheSystemsoftwarewasimplementedmainlyusingSimaticManager7andJava.TheSimaticManagerenvironmentisusedforcommunicationwiththePLCsystem.Theproposedarchitectureallowsforprogramming,reprogramming,andconfiguringthesystemremotely.TheJavaapplicationisdevelopedusingtheS7-APIs(S7-ApplicationProgrammingInterfaces)toestablishthecommunicationbetweentheDatabaseServerandPLCstation8.Forexample,usingtheseAPIs,wecaninstantiateobjectsthatwillconnecttheDatabaseServertothePLCstationbyspecifyingtheIPAddressandtheS7addressoftheCPUcontainedinthePLCunit.ThePLCisconnectedtotheprocesssensorsandactuatorsusingI/Omodules.AftertheJavaapplicationrunningontheserversideestablishestheconnectiontoPLCusingtheS7-APIs,itthenusestheJavaDatabaseConnectorTechnology(JDBC)tostoretheretrieveddatathatreflectsthestatusofvariousPLCparametersintheDatabaseTables.JDBCisatechnologythatallowsJavatoconnecttoDatabaseservers.ItcontainstherequiredJavalibrariesthatincludeallthenecessarymethodsrequiredtoconnecttotheDatabaseServerandexecuteSQLstatements.TheoverallsystemallowsuserstosetprocessvaluesusingthePLC.Forexample,userscansetanoutput(actuateamotor)orchangethevalueofamemorycell(memorybit,byte,word,flag,etc.).Thesystemenvironmentalsoprovidesforobtainingthereadingsofinputvalues(sensorsreadings)aswellascapturingthestatusofthePLC.AChartplottercanbeusedtoconvertreadingsfromthePLCsintocharts.Anerrorreportingmechanismthatprovidesadministratorswithusefuldiagnosticinformationisalsoincludedinthecompleteenvironment.SystemadministratorscanalsoquerythestatusoftheprocessusingtheGSMnetworkintheformofSMSmessages.Finally,theproposedsystemarchitectureisscalablewiththeabilitytomonitoracompletenetworkofPLCsspreadingaroundtheIntranetorInternet.3.SystemsoftwarearchitectureThesystemssoftwareusedinthisprojectisdividedintothreecomponents:AdatabasemanagementsystemApplicationmodules(datamanipulationmodules,PLCcommunicationmodulesandGSMmodemmodules)Auserinterface.Fig.3depictsthesystemssoftwaremajorcomponentsandthedirectionsofcommunicationbetweenthem.Adescriptionofeachcomponentisprovidedinthefollowingsubsections.3.1.AnoverviewofthedatabasesystemThedatabasewascreatedusingOracle9i.Itconsistsofasetofinter-relatedtables.Fig.4illustratesthedatabaseschemausedinthiswork.Forthesakeofbrevityabriefdescriptionofeachtableisprovidedbelow:AStationtablethatcontainstheentireinformationassociatedwiththePLCsuchasstationIPaddress,stationname,etc.APointerstablethatcontainsinformationabouteachInput,Outputor,Memorythatthesystemisusing.PointersrepresentaddressesforInput,Outputor,Memory.APointersreadingtableusedtostorethevaluesreadfromitemspointedtobythevariouspointers.Thistableissimilartoalogtablethatholdsthevariousstationsactivities.Fig.4.Databasetablesrelationships.160S.Danaetal./ComputerStandards&Interfaces30(2008)157166AnAdmintablecontainsalltheinformationonsystemusers.ARankattributeindicatesthesecuritylevelforeachadministrator,suchas,MainAdmin,Supervisor,andTrainee.Additionalinformationincludeloginname,password,aHintattributeforpasswordrecovery,etc.AClienttablecontainsalltheinformationpertainingtoeachclientthatisusingthesystemsuchasuseridentification,passwordandphone.Admin_PLCandClient_PLCtablesusedtosetthecorrespondingadminorclienttoaspecificstationid,andpointerid.3.2.ApplicationmodulesThesemodulesareattheheartofthesoftwarecomponentsoftheoverallsystem.TheymanagethecommunicationbetweentheuserinterfaceandtheDBMS.TheyinitiatetheconnectiontothePLCsystemandcontaintheneededobjectsforGSMcommunication.Theapplicationmodulesconsistoffollowingthreesubmodules:Adatamanipulationmodule:thismodulehasseveralclassesthatarecalledfromwithintheuserinterface(GUI)toperformvariousdatamanipulationtaskswithinthedatabasesuchas:insert,update,anddelete.Forexample,theinsertclassisresponsibleofinsertinganynewdatareceivedthroughtheuserinterface.APLCcommunicationmodule:thismoduleconsistsofthreeclasses;theyareusedtoperformtaskssuchasacceptingstationsIDfromusers,verifyingthateachstationhasapointerassociatedwithit,establishingconnectiontothePLCstation,etc.AGSMmodule:thismoduleprovidesforthecommunicationbetweentheGSMmodemandthecommunicationports.Thejavacommunicationpackageisused.Thispackageallowsjavatorecognizeboththeserialandtheparallelportsthatarepartofthesystem.ItcontainsthenecessaryfunctionsrequiredtosendandreceiveATcommandsandSMSmessagesthroughtheGSMmodem.3.3.TheuserinterfaceTheuserinterfaceusedinthisworkallowsusers(administratorsandclients)toaccessandmanipulatethedatabasetablesandtoissuebasiccontrolcommandstothedifferentPLCstations.Fordatabasemanipulationtheadministratordependingonhis/herrankcaninsert,update,orperformdifferentqueries.AdministratorscanalsoperformotheractivitiesusingthisGUIsuchassendingSMSmassagestodifferentclientsandadministrators.Dependingonhisorherrank,anadministratorcanentertheconfigurationarea,andperformactivitiessuchasviewingadminlogs,viewinghelpdocuments,viewingtutorialsofhowtousetheuserinterfaceaswellascontrollingsomeactivitiesinthestation.Fig.5showsoneoftheGUIscreensofthesystem.Thefigureshowsthedifferentfieldsthatcorrespondtothestationtableattributes.UserscanentervariousvaluespertainingtoaparticularstationsuchasitsIPaddress,itslocation,numberofinputsandmaximumnumberofoutputs.AsshownontheleftpaneloftheGUIinterface,usershavetheabilitytosearch,view,configure,andupdatetheinformationofaparticularstation.Fig.5depictsaGUIscreenfortheUpdatecommand.UsersmayusethiscommandtomodifyparticularstationinformationsuchasitsIPaddress,orlocation.Fig.6isasnapshotoftheGUIwheretheuserisembarkingonasearchtask.IntheshownsearchscreentheuserissearchingforaPLCstationbylocation.TheresponsetohissearchrequestisshowninFig.7.4.UsingTCP/IPtocommunicatewiththePLCTheCPmoduleisacommunicationprocessorfortheS7familythatallowsPLCstoconnecttoanIntranetortheInternetFig.5.AGUIdisplay.S.Danaetal./ComputerStandards&Interfaces30(2008)157166161inanyLANsetup.ThemodulesupportsthefollowingTCP/IPcommunicationservices7:SecureFTP(FileTransferProtocol)andHTTP(HyperTextTransferProtocol)serverloginwithuserIDsandpasswordSendE-mailmessageswithembeddedPLCdatatostandardSMTPmailserverFTPclientservicesforfiletransfertoaremoteserverFTPserverservicesforfiletransferto/fromaninternal8MBflashmemoryfilesystembyaremoteFTPclientHTTPserverservicesforremoteInternetbrowseraccessS7seriesprograminstructionsforInternetcommunication.Inadditionthemodulealsohasthefollowingfeatures:CommunicationbasedonTCP/IPandISOstandardsFactoryinstalledMACaddressPeer-to-peercommunicationcapabilitieswithotherS7devicesMultiple(upto8)connectionsEthernetclientorserverconfigurationoptionsPrograminstructionsforinitialization,reconfiguration,anddatatransfer.APLCcanbeprogrammedlocallyorremotelytosense,activateandcontrolindustrialequipmentandtherefore,incorporatesanumberofinput/outputterminalsthatareusedtointerfacethePLCtotheenvironmentorprocess.EachinputandoutputconnectionpointonaPLCmodulehasauniqueaddressthatidentifiesit.UsingtheTCP/IPprotocol,theIPaddressofthePLC,commandtypeandtheaddressoftheitem(I/Opoint)thatisreferencedareallcontainedintheIPpacket.TheIPaddressofthePLCisincludedintheheaderfield.ThepayloadfieldoftheIPpacketisallocatedtocarryvariousPLCFig.6.SampleGUIdisplay.Fig.7.Responsescreentoa“StationSearch”.162S.Danaetal./ComputerStandards&Interfaces30(2008)157166relatedparametersandcommands.Fig.8showsthecontentsoftheframesthataresentandreceivedfromthePLCsystem.TheMemoryParametersfieldcontainsinformation,suchastheaddressoftheitemtobemonitoredand/orcontrolled.Thisitemcanbeanyofthefollowing:InputOutputMemoryareaDatablock.Italsocontainsotherparameterssuchasdatatype(Boolean,integer,etc.),bitorbyteoffsetsandsoon.TheCommandTypefieldcontainsanyofthefollowingcommands:SetValueGetValueGetStatus.TheStatusfieldoftheframereturnsthestatusoftheaddresseditem.Thevaluefieldcontainsthevalueoftheaddresseditem.5.GSMaccessibilityForeseeingthepotentialofGSMservicesforlowvolumedatatransmissionandacquisition911wedecidedtoincorporatetheseservicesinoursystem.TheideahereisallowadministratorsandclientstoaccessthePLCsystemviatheGSMnetworkifneeded,andalsotobeabletoretrievevitalstatusinformationthroughit.TheJavacommunicationpackagewasusedtoallowforthecommunicationbetweentheGSMmodemandthevariousportsofthePLCsandtheserver.FortheGSMmodemthatisconnectedtothePLC,ladderdiagramsareusedtosendATAcommandsasstringstothemodem.SimilarlythereceivedSMSmessagesarereadasstrings.AmessagingcommunicationprotocolthatusesthepublicGSMservicesandissuitableforthisprojectwasdeveloped.Theprotocolusesvariousframestocommunicatewiththesystem.Fig.9depictstheformatusedforQueryframes.Abriefdescriptionofthevariousfieldsincludedintheaboveframeisgivenbelow.TypeofFrame(TOF):thisisa1bytefield.Theuser(administratororcustomer)shouldknowwhattypeofframehe/sheissending.Forthequeryframe,the“TypeofFrame”fieldshouldbesettothevalue1.C/A(Customer/Administrator):thisfieldindicateswhethertheuserisacustomerbywriting“c”oranadministratorbywriting“a”.Thisfieldhasasizeof1byte.UserID:thisfieldcontainsanIDforeachuser.Thelengthofthefieldis4bytes.Password:thisfieldindicateswhetherthepasswordbelongstoanadministratororaclient.Administratorshavefullaccessibilitytochangesensorsstatusbyusingthesetfunction,forexample.Themaximumlengthofthisfieldwillbe10byteswhichmeansthepasswordcantexceed10characters.StationID:thisfieldcontainstheStationIDnumber.Inthiswork,stationIDsareassumedtobeintherangeof1to9999.Thelengthofthisfieldis4bytes.PointerID:thisfieldhasthepointerIDnumber.ThepointersIDswillbeintherangeof1to9999.Thelengthofthisfieldis4bytes.TheQueryresponseframe:theresponseframewillbesentfromtheDatabasetotheadministratororclientwiththestatusofaspecificsensor.AframeillustrationisshowninFig.10.TheStationIDandPointerIDhavethesamemeaningasdescribedabove.TheValuefieldcontainsthereturnedvalueoftheitemwhosestatusisinterrogatedintheQueryframe.Notethatthefirst8bytesintheresponseframeareusedtostorethefollowingstring:“TheQueryResultsforPLC/PointerReadingis”.Fig.11showsanSMSresponsetoaquery.Fig.8.FramesusedtocommunicatewiththePLCsystemusingTCP/IP.Fig.9.MessagingformatfortheQueryframe.Fig.10.MessagingformatfortheResponseframe.S.Danaetal./ComputerStandards&Interfaces30(2008)157166163.Thequeryerrorframe:thisframewillbesenttotheAdministratororthecustomerviatheGSMnetworktoindicatethatanerrorhasoccurred.Thiserrorcanbeeitherinspecifyingthepassword,forexample,ortheStationIDdoesntexist,orthePointerIDdoesntexist.TheErrorframeformatisgiveninFig.12.Thefirst8bytesareusedtostorethestring:“Error:”.TheTypeofErrorfieldwillstateorclarifytheoriginoftheerror,forexample,acommandtypeisnotcorrect,orthePLCIDdoesnotexist.Commandframe:thecommandframecanbesentfromtheadministratortotheDatabaseServerorPLCseekingtochangethestatusofaspecificpointerusinga“setfunction”.ThedifferentframefieldsareshowninFig.13.Abriefdescriptionofeachfieldisprovidedbelow.TOF(TypeofFrame):Forthecommandframe,theTypeofFramefieldissettothevalue2.Value:thisfieldwillcontainthevaluethattheadministratorwantstosetthespecificaddresseditemto.Forexample,theBooleanwhichisusedtosetinputsandoutputssensorswillhavethevalueof0(false)and1(true).Therestofthefieldscarrythesamemeaningasdiscussedpreviously.Fig.14issnapshotofamobilescreencontainingacommandintheformofanSMSmessageusingtheframeformatdiscussedabove.Wealsoimplementeda“Reporting”mechanismbywhichSMSmessagesareautomaticallygeneratedandsenttotheadministratorperiodicallyorincaseofanemergency.ThesemessagescontainspecificcriticalstatusinformationaboutanyPLCstationthatmightrequireimmediateattention.Theimplementationofthismechanismisdetailedbelow.Thereportframe:theseframesaresentfromtheDatabaseServertotheadministrator.TherearetwotypesofReportsFrames:PeriodicalReports:sentperiodically(forexampleweekly)andareusedonlytoinformtheadministratoraboutthestatusofaStation.PeriodicalReportFrameshavetheformatdepictedinFig.15.Thefirst8bytesrepresentanormalStr