ANTILOCKBRAKINGSYSTEM

By

Y.Krishnakumar 08245A0303

T.Prashanth Babu 08245A0309

C.Karthik kumar 08245A0311

ABSTRACT

Intodaysworld,brakingisthemostimportantsysteminanAutomobile.

Brakesareenergyconversiondevices,whichconvertkineticenergyofthevehicleintothermalenergy.

InAntilockBrakingSystem,wecanpreventthelockingofthewheelandhenceskidding,usinganElectroMechanicalControlSystem

INTRODUCTION

Inrecentyears,withadvancementindesign&technology,Discbrakesarefastreplacingdrumbrakes.

ABSwasfirstdevelopedforAircraftsbrakingsystembutsoonstartedreplacingtheconventionalbrakingsystemintrucksandcars.

RecentimprovementsinABSallowstopreventwheelwhenacceleratedonwetorslipperysurface.

OPERATIONPRINCIPLE

Limitingthepressuretoanywheelwhichdeceleratestoorapidly isthebasicprincipleemployedinABS.

Aspeedsensorisusedformeasuringthespeedofthewheelandsendsitconstantlytothecomputer.

Dependingontheinitialbrakepressureandthespeedofthewheel,thecomputermodulatesthebrakepressureasfastasfifteentimespersecond.

STRUCTURE&OPERATIONOFTHEABS

TERMINOLOGY

ABSActuatorWorkhorseoftheABS. ABSChannel HydrauliclineconnectingABSactuatorandthewheel.

ABSSensorItconsistsagearshapedsensorrotorandsensorelement.

ABSValves Valvesareusedinbrakelineforcontrollingtheeachbrakedependingonitsposition.

TERMINOLOGY

ABSPumpsItisusedforpumpingthebackuppressurefromthereservoirtothebrakecylinder.

ABSPulseorModulation Thebrakingpressureisfluctuatingfifteentimespersecondforpreventingthelockingofthewheel.

DIFFERENTTYPESOFABSSYSTEMS

1or2channel2Wheel(RearABS) 2Channel4WheelCriss cross 3Channel4Wheel 4Channel4Wheel4Channel4Wheelisconsideredbetterthantheotherthreesystems.

ADVANTAGES

Itcanbeusedforreducingthestoppingdistance.

Itenablestosteerwhilethebrakesarefirmlyapplied

Itallowsbrakingfirmlyonsurfaceswithdifferentlevelofgrips.

Itcanreviewandadjustthedriversdriving.

DISADVANTAGES

DriversmaytakemoreriskswhendrivingwithvehiclesfittedwithABS.

Inexceptionalcircumstances,somedrivershavetheskilltostopthevehicleinashorterdistancethanachievedbyanABSequippedvehicle.

PeoplewhoareinexperiencedinusingABSmayrespondinappropriatelywhentheyactivatethesystem.

LUCASGIRLINGANTILOCKBRAKINGSYSTEM

HydraulicSystem Discbrakeshydraulicstotriggerbraking. Whenthedriverpressesonthebrakepedal,pistonismovedinthemastercylinder.

Thisincreasesthepressureinthemastercylinderwhichthenraisesthepressureinthebrakecylinder.

Thismakesthepistontomoveouttocontactthebrakepadsandengagesthebrakesagainsttherotor

Main Components of Disc Brakes System

-Wheel Shaft-Rotor/Disc-Caliper and its mounting-Brake Cylinders-Pistons-Brake Pads

WORKING Whenlockingoccurs,thecontrolvalveopensthepumpandreducesthepressureinthecavity.

Thentheactuatorslidesbackfurtherreducingthepressureinthecavitybecauseofvariablecrosssection.

Sincethelockingisnolongerimminentthecontrolvalvereturnsbacktooriginalposition.

Thisopensthevalveconnectingthemastercylindertothebrakingcylinderandnormaloperationofbrakecommences.

GYROSCOPICCOUPLE

Averticalreactionontheroadsurfacewillbeproducedduetogyroscopiccouple.

Theequationforthegyroscopiccoupleisgivenby

C=Cw CE=(wxp)(4xIwGxIE)

EXAMPLEPROBLEMTOUNDERSTANDANTILOCKBRAKINGSYSTEM

AVehiclemovesonleveltrackwiththespeedof72km/h.Thebrakesareappliedtofourwheelsandthecoefficientoffrictionis0.5.Findthetimetakenbythevehicletocometorest?

Sol:

ThedecelerationoftheVehicleisgivenby

a=gxfrictionalcoefficient.

a=gxcoefficient

=9.81x0.5

=4.905m/s2

Thetimetakenbythevehiclebeforecomingtorestisgivenbytheequation,

v=u+(axt)

0=20 (4.905xt)

t=4.077sec.

Att=3sec,v=5.285m/s.

Assumethatthevehiclewheellocksupafter3seconds,

ThenwithABSoperatedvehiclethebrakeisapplied15timespersecond.

Thevelocitiesateachpointafter3secondsareasfollows.

v1=5.059m/sv20=0.753m/sv2=4.833m/sv21=0.528m/sv3=4.578m/sv22=0.303m/sv4=4.353m/sv23=0.07m/sv5=4.128m/sv6=3.903m/sv7=3.678m/sv8=3.453m/sv9=3.228m/sv10=3.00m/sv11=2.778m/sv12=2.55m/sv13=2.32m/sv14=2.10m/sv15=1.87m/sv16=1.65m/sv17=1.42m/sv18=1.203m/sv19=0.978m/s

TotaltimetakenbyABSoperatedvehicle,

t=3+1.518

=4.518sec

Hence,thegyroscopiccoupleforcewillcomedowngraduallyinABSoperatedvehicle.

Thevehiclecomestoreduc restbying thisskiddingeffect.

CONCLUSION

Becauseofitsroleinpreventingthewheelsfromlockingandbettersteeringcontrolduringbraking,AntilockBrakingSystemshouldbemademandatoryforallvehicles.

REFERENCES

ThejournalsofSocietyofAutomotiveEngineersIndia(SAE India)

WilliamH.Crouse andDonaldL.Anglin,AutomotiveMechanics,10th Edition,Tata McGraw HillPublishingLimited.

TheoryofMachinesbyR.s.Kurmi

ANTI-LOCK BRAKING SYSTEMABSTRACTINTRODUCTIONOPERATION PRINCIPLESTRUCTURE & OPERATION OF THE ABSTERMINOLOGYTERMINOLOGYDIFFERENT TYPES OF ABS SYSTEMSADVANTAGESDISADVANTAGESLUCAS-GIRLING ANTILOCK BRAKING SYSTEMWORKINGGYROSCOPIC COUPLEEXAMPLE PROBLEM TO UNDERSTAND ANTI LOCK BRAKING SYSTEMCONCLUSIONREFERENCES