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1外文资料AgentcontrolledtrafficlightsIntroductionThequalityof(urban)trafficcontrolsystemsisdeterminedbythematchbetweenthecontrolschemaandtheactualtrafficpatterns.Iftrafficpatternschange,whattheyusuallydo,theeffectivenessisdeterminedbythewayinwhichthesystemadaptstothesechanges.Whenthisabilitytoadaptbecomesanintegralpartofthetrafficcontrolunititcanreactbettertochangesintrafficconditions.Adjustingatrafficcontrolunitisacostlyandtimelyaffairifitinvolveshumanattention.Thehypothesisisthatitmightofferadditionalbenefitusingself-evaluatingandself-adjustingtrafficcontrolsystems.Thereisalreadyamarketforanurbantrafficcontrolsystemthatisabletoreactiftheenvironmentchanges;thesocalledadaptivesystems.Realadaptivesystemswillneedpro-activecalculatedtrafficinformationandcycleplans-basedonthesecalculatedtrafficconditions-tobeupdatedfrequently.Ourresearchoftheusabilityofagenttechnologywithintrafficcontrolcanbesplitintotwoparts.Firstthereisatheoreticalpartintegratingagenttechnologyandtrafficcontrol.Thefinalstageofthisresearchfocusesonpracticalissueslikeimplementationandperformance.Herewepresenttheconceptsofagenttechnologyappliedtodynamictrafficcontrol.Currentlywearedesigningalayeredmodelofanagentbasedurbantrafficcontrolsystem.Wewillelaborateonthatinthelastchapters.AdaptiveurbantrafficcontrolAdaptivesignalcontrolsystemsmusthaveacapabilitytooptimisethetrafficflowbyadjustingthetrafficsignalsbasedoncurrenttraffic.Allusedtrafficsignalcontrolmethodsarebasedonfeed-backalgorithmsusingtrafficdemanddata-varyingfromyearstoacoupleofminutes-inthepast.Currentadaptivesystemsoftenoperateonthebasisofadaptivegreenphasesandflexibleco-ordinationin(sub)networksbasedonmeasuredtrafficconditions(e.g.,UTOPIA-spot,SCOOT).Thesemethodsarestillnotoptimalwheretrafficdemandchangesrapidlywithinashorttimeinterval.Thebasicpremiseisthatexistingsignalplangenerationtoolsmakerationaldecisionsaboutsignalplansundervaryingconditions;butalmostnoneofthecurrentavailabletoolsbehavepro-activelyorhavemeta-rulesthatmaychangebehaviourofthecontrollerincorporatedintothesystem.Thenextlogicalstepfortrafficcontrolistheinclusionofthesemeta-rulesandproactiveandgoal-orientedbehaviour.Thekeyaspectsofimprovedcontrol,forwhichcontributionsfromartificialintelligenceandartificialintelligentagentscanbeexpected,includethecapabilityofdealingwithconflictingobjectives;thecapabilityofmakingpro-activedecisionsonthebasisoftemporalanalysis;theabilityofmanaging,learning,selfadjustingandrespondingtonon-recurrentandunexpectedevents(Ambrosinoetal..,1994).Whatareintelligentagents?2Agenttechnologyisanewconceptwithintheartificialintelligence(AI).TheagentparadigminAIisbaseduponthenotionofreactive,autonomous,internally-motivatedentitiesthatinhabitdynamic,notnecessarilyfullypredictableenvironments(Weiss,1999).Autonomyistheabilitytofunctionasanindependentunitoveranextendedperiodoftime,performingavarietyofactionsnecessarytoachievepre-designatedobjectiveswhilerespondingtostimuliproducedbyintegrallycontainedsensors(Ziegler,1990).Multi-AgentSystemscanbecharacterisedbytheinteractionofmanyagentstryingtosolveavarietyofproblemsinaco-operativefashion.BesidesAI,intelligentagentsshouldhavesomeadditionalattributestosolveproblemsbyitselfinreal-time;understandinformation;havegoalsandintentions;drawdistinctionsbetweensituations;generalise;synthesisenewconceptsand/orideas;modeltheworldtheyoperateinandplanandpredictconsequencesofactionsandevaluatealternatives.Theproblemsolvingcomponentofanintelligentagentcanbearule-basedsystembutcanalsobeaneuralnetworkorafuzzyexpertsystem.Itmaybeobviousthatfindingafeasiblesolutionisanecessityforanagent.Oftenlocaloptimaindecentralisedsystems,arenottheglobaloptimum.Thisproblemisnoteasilysolved.Thesolutionhastobefoundbytailoringtheinteractionmechanismortohaveasupervisingagentco-ordinatingtheoptimisationprocessoftheotheragents.IntelligentagentsinUTC,ahelpfulparadigmAgenttechnologyisapplicableindifferentfieldswithinUTC.Theonesmostimportantmentioningare:informationagents,agentsfortrafficsimulationandtrafficcontrol.Currently,mostapplicationsofintelligentagentsareinformationagents.Theycollectinformationviaanetwork.Withspecialdesignedagentsuserspecificinformationcanbeprovided.Inurbantraffictheseintelligentagentsareuseableindeliveringinformationaboutweather,trafficjams,publictransport,routeclosures,bestroutes,etc.totheuserviaaPersonalTravelAssistant.Agenttechnologycanalsobeusedforaggregatingdataforfurtherdistribution.Agentsandmultiagentsystemsarecapableofsimulatingcomplexsystemsfortrafficsimulation.Thesesystemsoftenuseoneagentforeverytrafficparticipant(inasimilarwayasobjectorientedprogramsoftenuseobjects).Theapplicationofagentsin(Urban)TrafficControlistheonethathasourprimeinterest.Hereweultimatelywanttouseagentsforpro-activetrafficlightcontrolwithon-lineoptimisation.Signalplansthenwillbedeterminedbasedonpredictedandmeasureddetectordataandwillbetunedwithadjoiningagents.Themostpromisingaspectsofagenttechnology,theflexibilityandpro-activebehaviour,giveUTCthepossibilityofbetteranticipationoftraffic.CurrentUTCisn