automobile active safety technicalWord下载.docx

automobile active safety technicalWord下载.docx

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Introduction

IntheUnitedStatesin2011,therewereanaverageof82fatalmotorvehiclecrasheseverysingleday.Thesecrashesresultedinatotalof32,387deaths;

inthesameyear,therewere5,338,000motorvehicleaccidentsoverall[1].Theseshockingstatisticsplainlyillustratetheoften-underestimated​dangerinherentindrivingacar.Whilethesenumbersarestaggeringlyhigh,fortunatelytheyareindecline.Infact,thenumberoffatalitiesin2011wasthelowestsince1949,despitemanymoremilesbeingdrivenintotal.Muchofthissteadyreductioninthefrequencyandlethalityofcrashescanbeattributedtotheintroductionandwidespreadadoptionofnewautomotivesafetytechnologiesinthepastfewdecades.

Automotivesafetytechnologiescanbedividedintotwobasiccategories:

activeandpassivesafetysystems.Passivesafetysystemsarethosethatreducetheseverityofacrashonceithasoccurred;

theseincludenow-ubiquitoustechnologiessuchasairbags,seatbelts,andcrumplezones.Activesafetysystems,ontheotherhand,areengineeredtopreventaccidentsfromoccurringinthefirstplace.Thisisaccomplishedthroughvariousmethods,includingmakingthevehiclemorevisibletootherdrivers,betterinformingthedriverofroadhazards,andeventakingcontroloftheautomobiletopreventanaccident.Withtechnologieslikeenhancedheadlightsandradar-basedcollisionavoidance,activesafetysystemsrepresentavitallyimportantandrapidlydevelopingbranchofautomotiveengineering.

HistoryofAutomotiveActiveSafetySystems

WhenKarlBenzpatentedtheautomobilein1886,activesafetysystemswere,unsurprisingly,notpartofhisdesign.TheoriginalBenzPatentMotorwagenwaslittlemorethanamotorizedcarriage,withoutevenasimpleheadlightforvisibilityorconspicuity[2].Interestingly,significantsafetyimprovementsoverthatveryfirstautomobilewerealmostnonexistentforseveraldecades.Evenrudimentarypassivesafetysystemsonlybegantobeintroducedintheearly1930s,withbasicfeatureslikesafetyglassandpaddeddashboardsgraduallyappearinginpassengercars[3].Itwouldtakemanymoreyearsbeforeactivesafetysystemsbegantobeintroducedinautomobiles.Withtheexceptionofbasicvisibilitydevicessuchasheadlightsandmirrors,automotiveactivesafetysystemswerenonexistentuntilthedawnofthecomputeragebroughtabouttransformationalimprovementsinsafetytechnology.

D.Sikes/Flickr

Figure1:

Inrecentdecades,ABSandESChavereducedtheriskofautomobileaccidents,especiallywithdifficultroadconditions.

Madepossiblebythepoweroftheminiaturizedcomputer,theintroductionoftheanti-lockbrakingsystem（ABS）inthe1970’sandelectronicstabilitycontrol（ESC）inthe1990srevolutionizedautomobilesafety.Asoneofthefirstsafetysystemstotakecorrectiveactionandassistthedriverwithcontrollingthevehicleinunstablesituations（likepoorroadconditionsrelatedtoweatherasinFig.1,forexample）ESChadanespeciallysignificantimpact.TheInsuranceInstituteofHighwaySafety（IIHS）foundthatESCreducestheriskofsinglevehiclecrashesby40%,andreducestheriskoffatalcrashesbyamassive56%[4].Thesefiguresshowthetremendousimprovementthatactivesafetysystemsoffer,evenincarsalreadyprotectedbypassivesafetysystems.However,assignificantastheseadvanceswere,theyonlyrepresentthebeginningofthedevelopmentofactivesafetysystems.Newtechnologiesadoptedinthelastdecadeareonceagaincausingaparadigmshiftinautomobilesafety,affecting–andpotentiallysaving–thelivesofdriversaroundtheworld.

SituationalAwareness

Improvingthedriver’sawarenessofroadhazardsisthefoundationofsafedriving.Ifadriverisnotinformedquicklyofpotentialdangers,reactingappropriatelytothembecomesmoredifficultandtheprobabilityofanaccidentoccurringrisesdramatically.Sinceimprovingthedriver’sabilitytoanticipatedangerhassuchpotentialtoreducethefrequencyandseverityofaccidents,someofthemosteffectivemodernautomobilesafetytechnologiesfunctionbyenhancingthedriver’ssituationalawareness.

AdaptiveHeadlights

Ironically,oneofthemosteffectiveactivesafetytechnologiesemployedinvehiclestodayisbasedonthemostbasicofactivesafetydevices:

theheadlight.Alongwithmakingthevehiclehighlyvisibletootherdrivers,headlightsserveasimplepurpose:

illuminatingtheroadaheadatnight.However,standardheadlightsonlylightuptheterraindirectlyaheadofthecar;

thereisanunavoidablereductioninvisibilitywhendrivingintoacurve（Fig.2）asthelightpointsuselesslyofftheoutsideofthebend.Thislossofvisibilitycanleadtoadangeroussituationifthereisanobstacleinthecurvethatisnotilluminatedintimeforthedrivertoreact.

SebastianBallard/geograph.org​.uk

Figure2:

Narrow,curvedroadscanposegreatdangertothoseautomobilesnotoutfittedwithadaptiveheadlights.

However,automakershavedevisedaneffectivesolutiontothisdangerousshortcoming:

adaptiveheadlights.Adaptiveheadlightsturntoilluminatethevehicle’spathwheneveritturns,allowingthedrivertoseeintocurveswhendrivingatnight.Thisisaccomplishedbyhousingtheheadlightinanassemblythatcanberotatedhorizontallybysmallelectricmotorstopointtheheadlightsinthevehicle’sdirectionoftravel.Byrapidlyprocessinginformationsuchassteeringwheelangle,yaw,andthespeedofthevehicle,adaptiveheadlightscananticipatewherethecarisgoinganddirectthelightaccordingly.Adaptiveheadlightsanticipatethepathofthevehicleandturntoilluminatecurvesintheroadahead.

Whilethisimprovementinvisibilitymayseemminor,real-worlddataindicatesthatadaptiveheadlightsareahighlyeffectivesafetyfeature.InastudyconductedbytheIIHS,adaptiveheadlightswereresponsiblefora10%reductioninaccidentsincarsequippedwiththem[5].Ifeverycarontheroadwereequippedwithadaptiveheadlights,approximately142,000crashescouldbepreventedeveryyear[6].Clearly,theimprovementinvisibilityhasasignificantpositiveeffectonsafety,butadaptiveheadlightsonlyworkatnight.Otheractivesafetysystemsmustbeutilizedtowarndriversofthehazardsthatcanescapetheattentionofadrivereveninbroaddaylight.

BlindSpotInformationSystem

Avehicle’sblindspotrepresentsatreacherousgapinadriver’ssituationalawareness.Theblindspotisdefinedastheareaaroundthevehiclethatisobscuredfromthedriver’sview.Inpassengervehicles,thisismostcommonlythehiddenareathatliesbetweenthefieldofviewoftherearviewmirrorandsideviewmirrors.Ifadriverisunawarethatthereisanothervehiclehiddeninthecar’sblindspotandchangeslanessuddenly,acollisionislikelytoresult.Arecentlydevelopedprotectionagainstthisthreatistheblindspotinformationsystem（BLIS）.Thisactivesafetysystemusescamerasonthesideofthecartodetectthepresenceofothervehicleswithinthecar’sblindspotandalertsthedrivertotheirpresencewithawarninglightonthecorrespondingsideofthecar.Ifthedriveractivatestheturnsignalonthesideofthecarwheretheunseenhazardislurking,amoreintrusiveaudio,visual,orhapticwarningisissuedtourgentlydiscouragethedriverfromchanginglanes.

Theblindspotinformationsystemisavaluableadditiontothedriver’sownvisualinspectionofthesurroundingroad.However,asusefulaswarningtechnologieslikeBLIScanbeinpreventingaccidents,anewgenerationofactivesafetytechnologiesaimstomakedrivingsaferthaneverbycorrectingforthevehicle’smostunreliableelement:

itshumandriver.

DriverAssistance

Technologiessuchastheblindspotinformationsystemandactivesteeringheadlightscertainlymakedrivingasaferendeavor,buttheyhaveamajorshortcoming;

thedriveralonebearstheresponsibilityfortakingactiontoavoidadangeroussituation.Whilekeepingdriversinformedoftheirsurroundingsontheroadmakesavitalcontributiontosafety,humanerroroftenresultsinanaccidentdespitethefranticwarningofactivesafetysystems.Thisistheimpetusbehindtheriseofdriverassistancesystems:

technologiesthatnotonlywarnthedriverofhazards,butalsohavethecapabilitytotakepartialcontrolofthevehicletopreventacollision.

CollisionAvoidanceSystem

Rear-endcollisionsarethemostfrequentlyoccurringtypeofaccident,andtheyarealsoofteneasilypreventable[7].Inmanycases,adistracteddriverwillsimplyfailtonoticethattheleadingcarhasslowedorstoppedandcrashintoit,whichcouldbedeadlyforeitherdriverinvolvedatsufficientspeeds（Fig.3）.Thetechnologythatwasdevelopedtopreventthisisknownasthecollisionavoidancesystem.Collisionavoidancesystemsutilizearadarunitmountedinthefrontofthevehicletotrackthedistanceandspeedoftheleadingcar.Iftheradarsensesthattheleadingcarisslowingrapidly,awarningwillsoundtoencouragethedrivertobrake.Ifnoactionistakenandthedistancebetweenthetwovehiclesisdecreasingquicklyenoughtomakeanaccidentinevitable,thesystemwillautomatica