基于FPGA的交通灯设计(英文)

IEEEInternationalWorkshoponIntelligentDataAcquisitionandAdvancedComputingSystems:TechnologyandApplications6-8September2007,Dortmund,Germany1-4244-1348-6/07/$25.00©2007IEEE100FPGA-BasedAdvancedRealTrafficLightControllerSystemDesignWMEl-Medany1,MRHussain21)CEDepartment,ITCollege,UOB,[e-mail],~mbgedwme/2)GEOMATEC,SpatialInformationResearch,Manama,Bahrain,[e-mail]–Trafficlightcontrollerestablishesasetofrulesandinstructionsthatdrivers,pilots,trainengineers,andshipcaptainsrelyontoavoidcollisionsandotherhazards.Trafficcontrolsystemsincludesigns,lightsandotherdevicesthatcommunicatespecificdirections,warnings,orrequirements.Trafficlightcontroller(TLC)hasbeenimplementedusingmicrocontroller,FPGA,andASICdesign.FPGAhasmanyadvantagesovermicrocontroller,someoftheseadvantagesare;thespeed,numberofinput/outputportsandperformancewhichareallveryimportantinTLCdesign,atthesametimeASICdesignismoreexpensivethanFPGA.MostoftheTLCsimplementedonFPGAaresimpleonesthathavebeenimplementedasexamplesofFSM.ThispaperconcernedwithanFPGAdesignimplementationofalowcost24-houradvancedtrafficlightcontrollersystemthatwasbuiltasatermprojectofaVLSIdesignsubjectusingVHDL.TheimplementedtrafficlightisoneoftherealandcomplextrafficlightsinKingdomofBahrain,forfourroadsandmotorwaywithsensorsandcamera.ThesystemhasbeensuccessfullytestedandimplementedinhardwareusingXilinxSpartan3FPGA.ThesystemhasmanyadvantagesovertheexcitingTLC.Keywords-FPGA,Xilinx,VHDL,VLSI.I.INTRODUCTIONFieldprogrammablegatearrays(FPGAs)areextensivelyusedinrapidprototypingandverificationofaconceptualdesignandalsousedinelectronicsystemswhenthemask-productionofacustomICbecomesprohibitivelyexpensiveduetothesmallquantity[1].ManysystemdesignsthatusedtobebuiltincustomsiliconVLSI[2]arenowimplementedinFieldProgrammableGateArrays.ThisisbecauseofthehighcostofbuildingamaskproductionofacustomVLSIespeciallyforsmallquantity[3].Inthispaperthemainobjectivewastodesigna24-houretrafficlightcontrollertomanagethetrafficmovementoffourroadsatthesametime,andachievemaximumutilizationforthefourroads.Optimaltrafficlightcontrolisamulti-agentdecisionproblem,ourdesignlearnstheexpectedwaitingtimesofcarsforredandgreenlightsateachintersection[4,5,and6].Intherushhours,whenpeoplegoingtoworkorcomingbacktohomethetrafficlightsofallroadsarecontrolledwithfixedtime.However,inthenormaltime,themainroadsarecontrolledwithafixedtimewhilethenarrowroadsarecontrolledautonomouslybysensors[6,7,and8].Thematerialofthisarticleisarrangedasfollows:insectionII,wedescribethestructureofthefourroadsthathasbeenusedasanexampleforthedesignandthetimeallocatedforeachtrafficlight.DescriptionofthehardwaredesignandVHDLmodelisthesubjectofsectionIII.InsectionIVweexplainthestatediagramofthedesign.ThesimulationofthedesignandFPGAimplementationisstudiedinsectionV.FinallywediscussourresultsinsectionVI.II.STRUCTUREOFTHEFOURROADSTHATAREGOINGTOBECONTROLLEDFig.1showsthestructureofthefourroadsthathasbeenusedasapracticalexampletodesignourcontrollerwhicharelocatedinManamacity,KingdomofBahrain.Inthisstructurewehavesixtraffics,T1,T2,T3,T4,T5,andT6.ThemainroadsareT1andT3.ThereisalsoonecamerawhichisplacedonlyfortrafficT1.Thetimingforthetraffic’sisworkingasfollows:-T1andT3aregreenfor12seconds.-Othertrafficsaregreenfor6seconds.-Thegreentoyellowsignineachtrafficlighthas2secondsdelay.-Thereis2secondsafetyduringtransitionfromonetrafficlighttoanother(orfromoneroadtoanother).-Theredtoredyellowsignineachtrafficlighthas1seconddelay.Assumingthattheroadsarecrowded(allsensorsequaltologic‘1’);thenormalscenarioofthetrafficisasfollows:-ThesystemstartswithT1andT2havingthegreensign.-T1andT2willstaygreen,aftersixsecondsT2willturntoredandT3willbegreen.-AftertheremainingtimeforT1finishes,T1willturntoredandT4willbegreen.-AfterthetimeforT3andT4finishes,bothreturntored.ThenitistheturnforT5tobegreenforsixseconds.-FinallyT6willbecomegreenafterT5finishes.Table1showatimingstatesforthesixtrafficlightsforthegreenandredlightsonly.101Fig.1.TheFourRoadsStructure.Whatifsomeoftheroadsareempty(theirsensorsarelogic‘0’):Therearesomeprocedurestobedonebeforeturningfromonetrafficlighttoanother,andtheyareasfollows:-Ifthetimerofthecurrenttrafficfinishesandstilltherearecarsonitsroad,thetrafficwillnotgetredunlessitmakessurethatthereisanothertrafficwithsensor=logic‘1’.-Ifthereisnoothertraffichavingcars,sothecurrenttrafficwillstaygreenunlessoneofthetwoconditionsappears:1.Acarcameinothertrafficlight(sensorwillbelogic‘1’).Herethecurrenttrafficwillchangedtoredandtheothertrafficlightwillbegreen.2.Ifthesensorofthecurrenttrafficbecomelogic‘0’(meansthecarsinitsroadfinished)andstillothersensorsareequaltologic‘0’;HerethecurrenttrafficwillbeturnedtoredandT1andT3willbegreenasweassumedtheyarethetwomaintraffics(mainroads).Thesestepsaretheconditionsthathastobecheckedbeforeswitchingbetweenanytwotrafficsforthewholetimes(24-hours).ImportantNotes:-WhenT1isGreenT4,T5andT6shouldbeRed(T2orT3canbeGreenatthesametime).-WhenT2isGreenT4,T3,T5andT6shouldbeRed(T1isGreentoo).-WhenT3