智能城市交通系统外文翻译文献Word文档下载推荐.docx

智能城市交通系统外文翻译文献Word文档下载推荐.docx

《智能城市交通系统外文翻译文献Word文档下载推荐.docx》由会员分享，可在线阅读，更多相关《智能城市交通系统外文翻译文献Word文档下载推荐.docx（18页珍藏版）》请在冰点文库上搜索。

JohnFranceandAliA.Ghorbani

FacultyofComputerScience

UniversityofNewBrunswick

Fredericton,NB,E3B5A3,Canada

Abstract

Forthepurposesofmanaginganurbantrafficsystem,ahierarchicalmultiagentsystemthatconsistsofseverallocallyoperatingagentseachrepresentinganintersectionofatrafficsystemisproposed.LocalTrafficAgents（LTAs）areconcernedwiththeoptimalperformanceoftheirassigned

intersection;

however,theresultingtrafficlightpatternsmayresultinthefailureofthesystemwhenexaminedatagloballevel.Therefore,supervisionisrequiredandachievedwiththeuseofaCoordinatorTrafficAgent（CTA）.ACTAprovidesameansbywhichtheoptimallocallightpatterncanbecomparedagainsttheglobalconcerns.Thepatterncanthenbeslightlymodifiedtoaccommodatetheglobalenvironment,whilemaintainingthelocalconcernsoftheintersection.

Functionalityoftheproposedsystemisexaminedusingtwotrafficscenarios:

trafficaccidentandmorningrushhour.Forbothscenarios,theproposedmultiagentsystemefficientlymanagedthegradualcongestionofthetraffic.

1Introduction

The20thcenturywitnessedtheworldwideadoptionoftheautomobileasaprimarymodeoftransportation.Coupledwithanexpandingpopulation,present-daytrafficnetworksareunabletoefficientlyhandlethedailymovementsoftrafficthroughurbanareas.Improvementstoroadnetworksareoftenconfinedbytheboundariesofexistingstructures.Therefore,theprimaryfocusshouldbetoimprovetrafficflowwithoutchangingthelayoutorstructureoftheexistingroadways.Anysolutiontotrafficproblemmusthandlethreebasiccriteria,including:

dynamicallychangingtrafficpatterns,occurrenceofunpredictableevents,andanon-finitebasedtrafficenvironment[2].Multiagentsystemsprovidepossiblesolutionstothisproblem,whilemeetingallnecessarycriteria.Agentsareexpectedtoworkwithinareal-time,non-terminatingenvironment.Aswell,agentscanhandledynamicallyoccurringeventsandmaypossesseveralprocessestorecognizeandhandleavarietyoftrafficpatterns

[3,5].

Althoughseveralapproachestodevelopingamultiagenttrafficsystemhavebeenstudied,eachstressestheimportanceoffindingabalancebetweenthedesiresofthelocaloptimumagainstamaintainedaverageatthegloballevel[4].Unfortunately,systemsdevelopedtoonlyexamineandoptimizelocaleventsdonotguaranteeaglobalbalance[6].However,localagentsarefullycapableofdeterminingtheirownlocaloptimum.Therefore,amorepowerfulapproachinvolvesthecreationofahierarchicalstructureinwhichahigher-levelagentmonitorsthelocalagents,andisabletomodifythelocaloptimumtobettersuittheglobalconcerns[7].

Theremainderofthispaperisorganizedasfollows.Section2examinestheproblemsofurbantraffic.ThedesignofahierarchicalmultiagentmodelisgiveninSection3.TheexperimentalresultsarepresentedinSection4.Finally,theconclusionsofthepresentstudyaresummarizedinSection5.

2UrbanTrafficCongestion

Improvementstourbantrafficcongestionmustfocusonreducinginternalbottleneckstothenetwork,ratherthanreplacingthenetworkitself.Ofprimaryconcernistheoptimizationofthetrafficlights,whichregulatethemovementoftrafficthroughthevariousintersectionswithintheenvironment.

Atpresent,trafficlightsmaypossesssensorstoprovidebasicinformationrelatingtotheirimmediateenvironment.Thisincludesroadandclocksensors,measuringthepresenceanddensityoftrafficandprovidingthetimeofdaytothetrafficlight.

Asolutiontotheurbantrafficproblemusingagentsistosimplyreplacealldecision-makingobjectswithinthesystembyacorrespondingagent.Eventhemostbasicsystemwillconsistofseveralagents,leadingtothecreationofamultiagentenvironment.Inthiscase,thetrafficenvironmentisbrokendownintoitsfundamentalcomponents,withoneagentforeachofthetrafficlightswithinthesystem.TomaintainorganizationandcooperationbetweentheLocalTrafficAgents（LTA）,aCoordinatorTrafficAgent（CTA）existstomonitorglobalconcernsandmaintainorder.

3HierarchicalMultiagentModelforUrbanTraffic

Toachieveabalancebetweenthelocalandglobalaspectsofanurbantrafficsystem,amultiagentsystembasedonahierarchicalarchitectureisproposed.LTAsandCTAsmakeupthefundamentallevelsofthehierarchy,inwhichtheLTAsmeettheneedsofthespecificintersection,andtheCTAsdetermineifthechosenpatternsofaLTAaresuitedtomeetanyglobalconcerns.AsolitaryGlobalTrafficAgent（GTA）mayexistfornetworksofsufficientsize,andanInformationTrafficAgent（ITA）providesacentrallocationforthestorageofallsharedinformationwithinthesystem.Foreachagent,thevariablesnecessarytoorganizeandmaintainthehierarchyarelisted.

Thedevelopmentofthissystem,inwhichseveralLTAsworkundertheguidanceofasingleCTA,representsthebackbonetoahierarchicalstructureofagentswithinthesystem.TheCTAprovidesthebondsbetweenitselfandtheLTAsofthesystem,requiringthattheCTAstorealistoftheneighboringintersectionsforeachoftheLTAs.However,thecomputationalcapabilitiesofasingleCTAarelimited,andaroadnetworkofsufficientsizemayrequiretheuseofmultipleCTAstohandlealloftheLTAswithinthesystem.Inthiscircumstance,thenetworkwillbesubdividedintoregionscontrolledbyasingleCTA,withatop-levelGlobalTrafficAgent（GTA）linkingtheCTAstogether.TheGTAisanoptionalagent,existingonlyifthenetworkissufficientlylargethatitisrequired.

ALTAinteractsatagloballevelbysendingamessagecontainingthecalculatedoptimallocallightpatterntoitssupervisingCTA.TheCTAwillfindtheappropriateneighboringintersections,andthendeterminewhattheglobaloptimumforthehandledLTAwillbe.Tocalculatetheglobaloptimum,theCTAwillrequireallinformationrelatingtoeachoftheneighboringintersection.TheCTAwillrequesttheinformationfromtheITAbyprovidingalistoftheintersectionstheCTAisconcernedwith.Oncethisinformationisretrieved,aCTAcalculatestheglobaloptimumanddeterminesifavarianceexistsbetweenthelocalandglobaltrafficlightpatterns.Ifasignificantdifferenceisfound,abalancebetweenthelocalandglobaloptimumsmustbenegotiated,andthenreturnedtotheLTA.

4Implementation

TheproposedurbantrafficmultiagentsystemhasbeenimplementedusingtheJACKDevelopmentEnvironment,utilizingJACKIntelligentAgentsTM.JACKusestheBeliefDesireIntention（BDI）model.Underthisframework,“theagentpursuesitsgivengoals（desires）,adoptingappropriateplans（intentions）accordingtoitscurrentsetofdata（beliefs）aboutthestateoftheworld.”[1].AgentscreatedundertheJACKenvironmentareevent-driven,andcanrespondtointernalorexternaleventsoccurringwithinthesystem

ThefirstphaseofimplementingthemultiagentsysteminvolvesthecreationofLTAs.Eachoftheseagentsaretailoredtomeettherequirementsofitscorrespondingintersection.Forthepurposesofthisproject,thetrafficnetworkconsistsofsixintersections.Eachintersectionconsistsoftworoadscrossingoveroneanother.Eachapproachingroadpossestwolanes,aleft-turninglane,andastraight/rightturninglane.

Thedecision-makingcapabilitiesoftheLTAsisdevelopedinthesecondphase.ThefirstroundofdecisionsbyaLTAareconcernedwithfindingthelocaloptimum,withnoconsiderationforneighboringintersections.Abasicexpertsystemdividesthesensorinputsintoacorrespondinglightpattern.Theresultinglightpatternconsistsofaneight-elementarray,whichcanbebrokendownintotwoelementsforeachoftheNorth,East,SouthandWestdirections.

Oddelementsofthearray（zeroisthefirstindex）specifythedurationoftheadvancedgreenstateforeachoftheappropriatedirections,whileevenelementsindicatethetimeofthestraight/right-turninglanes.Thislightpatternisalwaysinthesameformat,andoncecalculated,storedbytheLTA.Thevaluescontainedwithinthearrayconsistofstrings,indicatingthedurationofthetrafficlight.Thevaluesofthestringsareasfollows:

Red:

Redlight,lanesremaininastoppedstate.

Short:

Greenlight,mostfrequentlyoccurring,30-secondsindurationforstraightdirections,15secondsforleftturninglanes.

Medium:

Greenlight,oftenforaboveaveragetrafficdensities,45-secondsindurationforstraightdirections,25secondsforleft-turninglanes

Greenlight,indicatingahightrafficdensity,60-secondsindurationforstraightdirections,35secondsforleft-turninglanes.

Oncetheoptimallocaltrafficlightpatterniscalculated,theLTAsendsamessageeventtotheCTA.ThetrafficlightpatternispassedtotheCTA,allowingtheCTAtoadjusttheLTA’slightpatterntobettermeetanyglobalconcerns.StoredwithintheCTAisavectorofneighborsforeachLTAwithinthesystem.WhenaCTAreceivesamessageeventfromaLTA,theCTAgathersallinformationrelatingtotheneighborsofthecurrentlyhandledLTAfromtheITA.TheCTAwillusethisinformationwithinitsownexpertsystem,comparingthelocaloptimumlightpatternagainstthecurrentdensitiesoftheneighboringintersections.Ifasignificantdifferenceisfoundbetweenthelocaloptimumandtheessenceoftheglobaloptimum,thetrafficlightpatterntobeimplementedisalteredtoreducethedifferencebetweenthetwooptimums.ThenewtrafficlightpatternisreturnedtotheLTAforimplementationwithinthetrafficlight