7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 1/15

SEMINAR REPORT

on

ANTI-LOCK BRAKING

SYSTEM

BACHELOR OF ENGINEERING

In

Electronics and Co!nication En"ineerin"

SRM #NI$ERSITY

S!%itted to & S!%itted %' &

Mrs( Anilet Bala Ms( )i*'a S+araSenior Mana"er $I Year , ECE 

B.TECH

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 2/15

)ECLARATION

I hereby declare that the seminar report is a record of bonafide work done by me under the

esteemed guidance of Mrs. Anilet Bala.

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 3/15

ACKNO.LE)GEMENT The success and final outcome of this project report required a lot of guidance and assistance

from many people and I am extremely fortunate to hae got this all along the completion of my

seminar report.

I owe my profound gratitude to our training guide Mrs. Anilet Bala who took keen

interest on my training and guided me all along! till the completion of my training by proiding

all necessary information.

  I heartily thank my course instructor! Mrs. Anilet Bala! "rofessor! #epartment of $lectronics

and %ommunication! for her aluable suggestions and time to time consultation. I am thankful to

and fortunate enough to get constant encouragement! support and constant guidance in this

course.

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 4/15

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 5/15

1.1 INTRODUCTION

Anti-lock brkin! "#"t$% (ABS) is an automobile safety system that allows

the wheels on a motor vehicle to maintain tractive contact with the road

surface according to driver inputs while braking, preventing the wheels from

locking up (ceasing rotation) and avoiding uncontrolled skidding. It is anautomated system that uses the principles of threshold braking and cadence

braking which were practiced by skillful drivers with previous generation

braking systems. It does this at a much faster rate and with better control

than a driver could manage.

ABS generally oers improved vehicle control and decreases stopping

distances on dry and slippery surfaces! however, on loose gravel or snow"

covered surfaces, ABS can signi#cantly increase braking distance, although

still improving vehicle control.

Since initial widespread use in production cars, anti"lock braking systems

have been improved considerably. $ecent versions not only prevent wheel

lock under braking, but also electronically control the front"to"rear brake

bias. %his function, depending on its speci#c capabilities and

implementation, is known as electronic brakeforce

distribution (&B'), traction control system, emergency brake assist,

or electronic stability control (&S).

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 6/15

1.& 'ORKING O( ABS

Stopping a car in a hurry on a slippery road can be very challenging. Anti"

lock braking systems (ABS) take a lot of the challenge out of this sometimes

nerve"wracking event. In fact, on slippery surfaces, even professional drivers

cant stop as *uickly without ABS as an average driver can with ABS.In this article, the last in a si+"part series on brakes, well learn all about anti"

lock braking systems "" why you need them, whats in them, how they work,

some of the common types and some associated problems.

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 7/15

1.) HISTORY 

1.3.1 Early systems

ABS was #rst developed for aircraft use in -- by the/rench automobile and aircraft pioneer 0abriel 1oisin, as threshold

braking on airplanes. %hese systems use a 2ywheel and valve attached to a

hydraulic line that feeds the brake cylinders. %he 2ywheel is attached to a

drum that runs at the same speed as the wheel. In normal braking, the drum

and 2ywheel should spin at the same speed. 3owever, when a wheel slows

down, then the drum would do the same, leaving the 2ywheel spinning at a

faster rate. %his causes the valve to open, allowing a small amount of brake

2uid to bypass the master cylinder into a local reservoir, lowering the

pressure on the cylinder and releasing the brakes. %he use of the drum and

2ywheel meant the valve only opened when the wheel was turning. Intesting, a 456 improvement in braking performance was noted, because the

pilots immediately applied full brakes instead of slowly increasing pressure in

order to #nd the skid point. An additional bene#t was the elimination of

burned or burst tires.

By the early -75s, the 'unlop 8a+aret anti"skid system was in widespread

aviation use in the 9:, with aircraft such as the Avro 1ulcan and 3andley

;age 1ictor, 1ickers 1iscount, 1ickers 1aliant, &nglish &lectric <ightning, de

3avilland omet c, de 3avilland Sea 1i+en, and later aircraft, such as

the 1ickers 15, 3awker Siddeley %rident,3awker Siddeley 7, 3awker

Siddeley 3S =>? and derived British Aerospace A%;, and BA @ne"&leven being #tted with 8a+aret as standard.7 8a+aret, while reducing

braking distances by up to 456 in icy or wet conditions, also increased tyre

life, and had the additional advantage of allowing take"os and landings in

conditions that would preclude 2ying at all in non"8a+aret e*uipped aircraft.

In -7?, a $oyal &n#eld Super 8eteor motorcycle was used by the $oad

$esearch <aboratory to test the 8a+aret anti"lock brake.C %he e+periments

demonstrated that anti"lock brakes can be of great value to motorcycles, for

which skidding is involved in a high proportion of accidents. Stopping

distances were reduced in most of the tests compared with locked wheel

braking, particularly on slippery surfaces, in which the improvement could beas much as 45 percent. &n#elds technical director at the time, %ony Dilson"

 Eones, saw little future in the system, however, and it was not put into

production by the company.

A fully mechanical system saw limited automobile use in the -C5s in

the /erguson ;-- racing car, the Eensen //, and the e+perimental all wheel

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 8/15

drive /ord Fodiac, but saw no further use! the system proved e+pensive and

unreliable.

 %he #rst fully electronic anti lock system was developed in the late C5s for

the oncorde aircraft.

1.3.2 Modern systems

hrysler, together with the Bendi+ orporation, introduced a computeriGed,

three"channel, four"sensor all"wheel ABS called HSure BrakeH for its

-= Imperial. It was available for several years thereafter, functioned as

intended, and proved reliable. In -=5, /ord added an antilock braking

system called HSure"trackH to the rear wheels of <incoln ontinentals as an

option! it became standard in -=. In -=, 0eneral 8otors introduced the

H%rackmasterH rear"wheel only ABS as an option on their rear"wheel

driveadillac models and the @ldsmobile %oronado. In the same

year, issan oered an &A< (&lectro Anti"lock System) as an option on

the issan ;resident, which became Eapans #rst electronic ABS.

-=J &lectronically controlled anti"skid brakes on %oyota rownC In -=,

four wheel drive %riumph 755 &states were #tted with 8ullard electronic

systems as standard. Such cars were very rare however and very few survive

today.

In -?7 the /ord Scorpio was introduced to &uropean market with a %eves

electronic system throughout the range as standard. /or this the model was

awarded the coveted&uropean ar of the Kear Award in -?C, with very

favourable praise from motoring Lournalists. After this success /ord began

research into Anti"<ock systems for the rest of their range, which encouraged

other manufacturers to follow suit.

In -??, B8D introduced the #rst motorcycle with an electronic"hydraulic

ABSJ the B8D :55. 3onda followed suit in -- with the launch of its #rst

motorcycle ABS on theS%55 ;an &uropean. In 55=, SuGuki launched

its 0S/55SA (Bandit) with an ABS. In 557, 3arley"'avidson began oering

an ABS option on police bikes.

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 9/15

1.* O+ERATION

 %he anti"lock brake controller is also known as the AB (ontroller Anti"lock

Brake).

 %ypically ABS includes a central electronic control unit (&9), four wheelspeed sensors, and at least two hydraulic valves within the brake hydraulics.

 %he &9 constantly monitors the rotational speed of each wheel! if it detects

a wheel rotating signi#cantly slower than the others, a condition indicative of 

impending wheel lock, it actuates the valves to reduce hydraulic pressure to

the brake at the aected wheel, thus reducing the braking force on that

wheel! the wheel then turns faster. onversely, if the &9 detects a wheel

turning signi#cantly faster than the others, brake hydraulic pressure to the

wheel is increased so the braking force is reapplied, slowing down the wheel.

 %his process is repeated continuously and can be detected by the driver via

brake pedal pulsation. Some anti"lock systems can apply or release brakingpressure 7 times per second. Because of this, the wheels of cars e*uipped

with ABS are practically impossible to lock even during panic braking in

e+treme conditions.

 %he &9 is programmed to disregard dierences in wheel rotative speed

below a critical threshold, because when the car is turning, the two wheels

towards the center of the curve turn slower than the outer two. /or this same

reason, a dierential is used in virtually all roadgoing vehicles.

If a fault develops in any part of the ABS, a warning light will usually be

illuminated on the vehicle instrument panel, and the ABS will be disabled

until the fault is recti#ed.

8odern ABS applies individual brake pressure to all four wheels through a

control system of hub"mounted sensors and a dedicated micro"controller.

ABS is oered or comes standard on most road vehicles produced today and

is the foundation for electronic stability control systems, which are rapidly

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 10/15

increasing in popularity due to the vast reduction in price of vehicle

electronics over the years.

8odern electronic stability control systems are an evolution of the ABS

concept. 3ere, a minimum of two additional sensors are added to help the

system workJ these are asteering wheel angle sensor, anda gyroscopic sensor. %he theory of operation is simpleJ when the gyroscopic

sensor detects that the direction taken by the car does not coincide with

what the steering wheel sensor reports, the &S software will brake the

necessary individual wheel(s) (up to three with the most sophisticated

systems), so that the vehicle goes the way the driver intends. %he steering

wheel sensor also helps in the operation of ornering Brake ontrol (B),

since this will tell the ABS that wheels on the inside of the curve should brake

more than wheels on the outside, and by how much.

ABS e*uipment may also be used to implement a traction control

system (%S) on acceleration of the vehicle. If, when accelerating, the tireloses traction, the ABS controller can detect the situation and take suitable

action so that traction is regained. 8ore sophisticated versions of this can

also control throttle levels and brakes simultaneously

1., COM+ONENTS

 %here are four main components of ABSJ speed sensors, valves, a pump, and

a controller.

 1.5.1 Speed sensors

A speed sensor is used to determine the acceleration or deceleration of the wheel. %hese sensors use a magnet and a coil of wire to generate a signal. %he rotation of

the wheel or dierential induces a magnetic #eld around the sensor. %he

2uctuations of this magnetic #eld generate a voltage in the sensor. Since the

voltage induced in the sensor is a result of the rotating wheel, this sensor can

become inaccurate at slow speeds. %he slower rotation of the wheel can cause

inaccurate 2uctuations in the magnetic #eld and thus cause inaccurate readings to

the controller.

1.5.2 Valves

 %here is a valve in the brake line of each brake controlled by the ABS. @n some

systems, the valve has three positionsJ

• In position one, the valve is open! pressure from the master cylinder is

passed right through to the brake.

• In position two, the valve blocks the line, isolating that brake from the master

cylinder. %his prevents the pressure from rising further should the driver push

the brake pedal harder.

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 11/15

• In position three, the valve releases some of the pressure from the brake.

 %he maLority of problems with the valve system occur due to clogged valves. Dhen

a valve is clogged it is unable to open, close, or change position. An inoperable

valve will prevent the system from modulating the valves and controlling pressure

supplied to the brakes.

1.5.3 Pump

 %he pump in the ABS is used to restore the pressure to the hydraulic brakes after

the valves have released it. A signal from the controller will release the valve at the

detection of wheel slip. After a valve release the pressure supplied from the user,

the pump is used to restore a desired amount of pressure to the braking system.

 %he controller will modulate the pumps status in order to provide the desired

amount of pressure and reduce slipping.

1.5.4 Controller 

 %he controller is an &9 type unit in the car which receives information from each

individual wheel speed sensor, in turn if a wheel loses traction the signal is sent to

the controller, the controller will then limit the brake force (&B') and activate the

ABS modulator which actuates the braking valves on and o.

1. USES

 %here are many dierent variations and control algorithms for use in ABS. @ne of

the simpler systems works as followsJ

. %he controller monitors the speed sensors at all times. It is looking for

decelerations in the wheel that are out of the ordinary. $ight before a wheel

locks up, it will e+perience a rapid deceleration. If left unchecked, the wheel

would stop much more *uickly than any car could. It might take a car #ve

seconds to stop from C5 mph (-C.C kmMh) under ideal conditions, but a wheel

that locks up could stop spinning in less than a second.

. %he ABS controller knows that such a rapid deceleration is impossible, so it

reduces the pressure to that brake until it sees an acceleration, then itincreases the pressure until it sees the deceleration again. It can do this very

*uickly, before the tire can actually signi#cantly change speed. %he result is

that the tire slows down at the same rate as the car, with the brakes keeping

the tires very near the point at which they will start to lock up. %his gives the

system ma+imum braking power.

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 12/15

4. %his replaces the need to manually pump the brakes while driving on a

slippery or a low traction surface, allowing to steer even in the most

emergency braking conditions.

>. Dhen the ABS is in operation the driver will feel a pulsing in the brake pedal!

this comes from the rapid opening and closing of the valves. %his pulsing also

tells the driver that the ABS has been triggered. Some ABS systems can cycleup to C times per second.

1. BRAKE TY+ES

Anti"lock braking systems use dierent schemes depending on the type of brakes in

use. %hey can be dierentiated by the number of channelsJ that is, how many

valves that are individually controlledNand the number of speed sensors.

1.7.1 Four-cannel! "our-sensor #$S

 %his is the best scheme. %here is a speed sensor on all four wheels and a separate

valve for all four wheels. Dith this setup, the controller monitors each wheel

individually to make sure it is achieving ma+imum braking force.

1.7.2 %ree-cannel! "our-sensor #$S

 %here is a speed sensor on all four wheels and a separate valve for each of the front

wheels, but only one valve for both of the rear wheels. @lder vehicles with four"

wheel ABS usually use this type.

1.7.3 %ree-cannel! tree-sensor #$S

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 13/15

 %his scheme, commonly found on pickup trucks with four"wheel ABS, has a speed

sensor and a valve for each of the front wheels, with one valve and one sensor for

both rear wheels. %he speed sensor for the rear wheels is located in the rear a+le.

 %his system provides individual control of the front wheels, so they can both achieve

ma+imum braking force. %he rear wheels, however, are monitored together! they

both have to start to lock up before the ABS will activate on the rear. Dith this

system, it is possible that one of the rear wheels will lock during a stop, reducing

brake eectiveness. %his system is easy to identify, as there are no individual speed

sensors for the rear wheels.

1.7.4 %&o-cannel! "our sensor #$S

 %his system, commonly found on passenger cars from the late ?5s through early

555s (before government mandated stability control), uses a speed sensor at each

wheel, with one control valve each for the front and rear wheels as a pair. If the

speed sensor detect lock up at any individual wheel, the control module pulses the

valve for both wheels on that end of the car.

1.7.5 'ne-cannel! one-sensor #$S

 %his system is commonly found on pickup trucks with rear"wheel ABS. It has one

valve, which controls both rear wheels, and one speed sensor, located in the rear

a+le. %his system operates the same as the rear end of a three"channel system. %he

rear wheels are monitored together and they both have to start to lock up before

the ABS kicks in. In this system it is also possible that one of the rear wheels will

lock, reducing brake eectiveness. %his system is also easy to identify, as there are

no individual speed sensors for any of the wheels.

1./ E((ECTI0ENESS

A 55> Australian study by 8onash 9niversity Accident $esearch entre found that

ABSJ

• $educed the risk of multiple vehicle crashes by ? percent,

• Increased the risk of run"o"road crashes by 47 percent.

@n high"traction surfaces such as bitumen, or concrete, many (though not all) ABS"

e*uipped cars are able to attain braking distances better (i.e. shorter) than those

that would be possible without the bene#t of ABS. In real world conditions, even an

alert and e+perienced driver without ABS would #nd it diOcult to match or improve

on the performance of a typical driver with a modern ABS"e*uipped vehicle. ABS

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 14/15

7/21/2019 Seminar Report

http://slidepdf.com/reader/full/seminar-report-56da1fec1e6bb 15/15

that ABS would take care of them, while the non"ABS drivers drove more carefully

since ABS would not be there to help in case of a dangerous situation.

 %he Insurance Institute for 3ighway Safety released a study in 55 that found

motorcycles with ABS 4=6 less likely to be involved in a fatal crash than models

without ABS.