汽車專業(yè)英語讀譯教程 第3版 課件 22-U13TA Computers on Modern Vehicles

UNIT13

AUTOMOTIVECOMPUTERSAND

COMMUNICATIONSYSTEM

TEXTA

ComputersonModernVehicles

PROFESSIONALENGLISHTEXTA

ComputersonModernVehicles

Computers

CentralProcessingUnit

TemporaryComputerMemory

PermanentComputerMemory

ComputerControlOperation

OpenandClosedLoopOperation

InputSensors

OutputDevices本次課學(xué)習(xí)內(nèi)容本次課學(xué)習(xí)目標(biāo)掌握automotivecomputer的英文專業(yè)詞匯訓(xùn)練快速閱讀能力，提高閱讀速度NEWWORDSdefective[di'fektiv]a.有缺陷的,損壞的，有故障的affix[?'fiks]v.使附于,粘貼，使固定revise[ri'vaiz]v.修訂,修正,修改nonvolatile['n?n'v?l?tail]a.非易失性的ultraviolet['?ltr?'vai?lit]a.紫外線的,紫外的random['r?nd?m]a.任意的,隨機(jī)的;n.隨意,任意volatile['v?l?tail]a.可變的,易失的，不穩(wěn)定的fuelmileage燃油經(jīng)濟(jì)性burnin燒上，烙上，腐蝕，留下不可磨滅的印象volatilememory易失存儲(chǔ)器keepalivememory(KAM)可保持存儲(chǔ)器(KAM)readonlymemory(ROM)只讀存儲(chǔ)器(ROM)programmablereadonlymemory(PROM)可編程只讀存儲(chǔ)器(PROM)erasableprogrammablereadonlymemory(EPROM)可擦可編程只讀存儲(chǔ)器(EPROM)NEWWORDSelectronicallyerasableprogrammablereadonlymemory(EEPROM)電可擦可編程只讀存儲(chǔ)器(EEPROM)overandover反復(fù)innature本質(zhì)上，實(shí)際上NEWWORDSAlmosteveryvehiclebuiltinthelast10-15yearshasatleastoneon-boardcomputer.Theremaybeuptosixdifferentcomputersonsomevehicles.On-boardcomputerscontrolignitionandfuelsystems,emissioncontrols,coolingfans,airconditionercompressor,torqueconverterclutch,andtransmissionshiftpoints.Othervehiclecomputerscontroltheairbags,anti-lockbrakeandtractioncontrolsystems,interiorairtemperatureanddistribution,suspensionandsteeringsystems,andtheanti-theftsystem.Manymodernvehiclescombinetheenginecontro1computerandothervehiclecomputersintoonelargemicroprocessor,whichmonitorsandcontrolsmostvehiclefunctions.ComputersonModernVehicles

Theprimaryreasonforusingon-boardcomputersinmodernvehiclesistomeetfueleconomyandemissionsregulations.Theuseofcomputersallowstheignition,fuel,andemissionsystemsoperationstobecontrolledprecisely.Theendresultisastoichiometricair-fuelratiothatisascloseto14.7:1aspossible.Thisair-fuelratioisnecessaryforoptimumcatalyticconverteroperationaswellasgoodfueleconomyandemissionsperformance.Neweron-boardcomputersalsocontrolthetorqueconverterclutch,transmissionshiftpoints,andairconditioneroperationtoincreasefuelmileageaswellasloweremissions.Thecomputercontrolsystemcanbedividedintothreemajorsubsystems:computer,inputsensorsandoutputdevices.ComputersonModernVehiclesComputersAvehicle'son-boardcomputerisnormallyreferredtoasanelectroniccontrolunitorECU.TheECUhasmanydifferentnames.Avehicle'sECUmaybereferredtobyoneofthefollowingterms:·controller·microprocessor·on-boardcomputer·enginecontrolcomputer(ECC)·engineorelectroniccontrolmodule(ECM)·powertraincontrolmodule(PCM)Thesenamesarethemostcommonanddependingonthemanufacturerandvehiclesystem[1],otherspecificnamesmaybeused.ECU'sareusuallycontainedinonecasing.MostECU'sarelocatedinsidethevehicle'sinteriorawayfromtheheatandvibrationoftheenginecompartment,butcanbelocatedalmostanywheredependingonthevehicle,system,andmanufacturer.ComputersonModernVehiclesAfewECUsaremadeintwoparts,withtheprocessorlocatedinthepassengercompartmentandtheoutputpartunderthehood.Whatevertheirphysicallocations,allECUscontaintwomainsections:thecentralprocessingunitandthememorysection.Thememorysectionhastwoseparatesectionsofmemory--permanentandtemporary.CentralProcessingUnitThecentralprocessingunit(CPU)isthesectionoftheelectroniccontrolunitthatperformscalculationsandmakesdecisions.TheCPUissometimescalledthecontroller.TheCPUisconstructedusingoneormoreintegratedcircuits,orICs.IncomingdatafromtheinputsensorsmustgothroughtheCPU,wherethedataisprocessedandadjustmentsmadetotheoutputsensors.TheECUmustbereplacediftheCPUisdefective,asitisaffixedtotheECU'scircuitboard.ComputersonModernVehiclesPermanentComputerMemoryTherearefourbasictypesofpermanentcomputermemory,readonlymemory(ROM),programmablereadonlymemory(PROM),erasableprogrammablereadonlymemory(EPROM),andelectronicallyerasableprogrammablereadonlymemory(EEPROM).AprogramthattellstheECUwhattodoandwhentodoitisstoredinROM.TheROMalsocontainsgeneralinformationthatisusedasastandardofoperationundervariousconditions.Oncethisinformationisplacedinmemory,itcannotbemodified.TheROMisanintegralpartoftheECU.IftheROMisdefective,theECUmustbereplaced.ComputersonModernVehiclesProgrammablereadonlymemory(PROM)isavariationofROM.Onsomevehicles,thePROMispluggedintotheECUandcanbereplacedifitisdefectiveorifarevisedPROMisneeded.ThiseliminatestheexpenseofreplacingtheentireECU.Onmostnewervehicles,thePROMispermanentlyaffixedtotheECU.TheROMandPROMarenonvolatilememories.Thismeansthatinformationstoredinthesememorieswillremainevenifthebatteryisdisconnected.TheEPROMcanbereprogrammedbyexposingittoultravioletlightandthenreprogrammingit.Thiscanonlybedonebythemanufacturer.TheEEPROMcanbeerasedelectronicallyandreprogrammedor"burnedin",usingeitherelectronicscantoolsorcomputerizeddiagnosticequipment.ComputersonModernVehiclesTemporaryComputerMemoryTheECUusesrandomaccessmemory(RAM)asatemporarystorageplacefordatafromthesensors.Asnewinformationisreceivedfromthesensors,itiswrittenovertheoldinformationinsidetheRAM.TheECUconstantlyreceivesnewsignalsfromthesensorswhiletheengineisrunning.IfnosignalorthewrongsignalisreceivedbytheECU,adiagnostictroublecodeisstoredintheRAM.TheRAMiscontainedinsidetheECU.IftheRAMisdefective,theECUmustbereplaced.TheRAMhasavolatilememory.Thismeansthatifthebattery,fuse,orthepowersourceattheECUisdisconnected,alldataintheRAMwillbeerased,includinganystoredtroublecodes.SomeECUsuseanothertypeofmemorycalledkeepalivememory(KAM).ComputersonModernVehicles

KAMisamemorychipthatallowstheECUtomaintainnormalvehicleperformancebycompensatingforsensorandpartswear.Thisissometimescalledanadaptivestrategy.AnydatainKAMisalsolostifpowertotheECUisdisconnected.ComputerControlOperationAlthoughitisfarsimpler,thecomputercontrolsystemoperatesinmuchthesamewayasthehumannervoussystem.Ifyoutouchahotenginepart,thenervesinyourhandsendasignaltoyourbrain.Basedonthesignal,yourbraindecidesthatyourhandmaygetburnedandtellsyourarmmusclestopullyourhandawayfromthepart.AnECUreceivesinputdataintheformofelectricalsignalsfromthesensors(nerves).TheECU(brain)comparestheinputdatatothestandardsintheROM.Basedonitscalculations，theECUsendscommandstotheoutputdevices(armmuscles).Thisprocessisperformedoverandoverasengine,environmental,andvehicleconditionschange.ComputersonModernVehiclesOpenandClosedLoopOperationWhentheengineiscold,itcannotprovideoptimumfueleconomyandemissionscontrol.Also,severaloftheinputsensorsmustwarmuptooperatingtemperaturebeforetheycanprovidereliablereadings.Therefore,whileoneormoreoftheinputsensorstellstheECUthattheengineisbelowacertaintemperature,theECUoperatesinopenloopmode.Inopenloopmode,theECUcontrolstheair-fuelratiobasedonpresetinformationwhilemonitoringtheinputsensorreadings.Somecomputercontrolsystemsalsogointoopenloopmodewhenthethrottleisopenedcompletely,oftencalledwideopenthrottlemode.

ComputersonModernVehiclesWhentheinputsensorstelltheECUthattheenginehaswarmedupsufficiently,theECUgoesintoclosedloopmode.Intheclosedloopmode,theECUbeginsprocessingtheinformationfromtheinputsensorsandbasesitscommandstotheoutputdevicesonthesensorinformation.Theresultisoptimumfueleconomyandengineperformancewithminimalemissionsoutput.ComputersonModernVehiclesInputSensorsTheelectroniccontrolunitreceiveshundredsofinputsignalseverysecond.Thesesignalsarecreatedbyinputsensors.Eachsensormeasuresoneoperatingconditionoftheengineordrivetrain.ThesensorthensendsanelectricalsignalthatrepresentsthemeasurementtotheECU.SomesensorsproducetheirownvoltagesignalandothersensorsadjustthevoltagesenttoitbytheECU,ThevoltagesenttothesesensorsbytheECUiscalledthereferencevoltage.TheamountofresistanceatthesensordetermineshowmuchoutputvoltageissenttotheECU.TheECUthencomparesitsreferencevoltagetothesensoroutputvoltage.Thisdet