JJ 615 MECHANICAL MAINTENANCE AND COMPONENT

CASE STUDY

ANTI-LOCK BRAKING SYSTEM

LECTURER’S NAME : EN. WAN MOHD NAGUIB BIN WAN ABD. RAHMAN

NAME MATRIC NO.MUHAMMAD HAFFADZIL

BIN ZAINUDDIN15DKM12F1021

CONTENT

Content Pages1.0 Abstract 12.0 Objective 13.0 Introduction 24.0 Supporting Statement 35.0 Conclusion 36.0 References 3

1.0 ABSTRACT

Anti-lock braking system (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 and avoiding uncontrolled skidding. It is

an automated 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 offers improved vehicle control and decreases stopping distances on dry and

slippery surfaces for many drivers; however, on loose gravel or snow-covered surfaces, ABS can

significantly increase braking distance, although still improving vehicle control.

2.0 OBJECTIVE

1. Learn how the anti-lock braking system work to the automobile brake.

2. Determine about what is the anti-lock braking system and why this system can

maintain tractive contact with the road surface to driver.

3. Learn how to make a maintenace when using this anti-lock braking system.

4. Analyze brake system design parameters and their vehicle performance effects.

3.0 INTRODUCTION

3.1 WHAT IS ANTI-LOCK BRAKING SYSTEM (ABS)

Anti-lock braking system is an automobile safety system prevent the wheels of a vehicle

locking as brake pedal pressure is applied often suddenly in an emergency or short stopping

distance. This enables the driver to have a steering control, preventing skidding and loss of

traction.

Anti-lock braking system (ABS) is an automobile safetysystem that allows

the wheels on a motor vehicle to maintaintractive 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 an automated 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 offers improved vehicle control and decreases stopping distances on dry

and slippery surfaces for many drivers. However, on loose gravel or snow-covered surfaces,

ABS can significantly increase braking distance, although still improving vehicle control. Since

initial widespread use in production cars, anti-lock braking systems have been improved

considerably. Recent versions not only prevent wheel lock under braking, but also electronically

control the front-to-rear brake bias. This function, depending on its specific capabilities and

implementation, is known as electronic brakeforce distribution(EBD), traction control system,

emergency brake assist, or electronic stability control(ESC).

A brake is one of most important part of any type of vehicle. Brake is used to retard or

stop a vehicle. Here kinetic energy transferred into Heat energy. The kinetic energy increases

with the square of the velocity. So, K.E = 1/2mv2. An anti-lock braking system is a safety that

allows the wheels on a motor vehicle to continue interacting tractively with the road surface as

directed by driver steering inputs while braking, preventing the wheels from locking up (that is,

ceasing rotation) and therefore avoiding skidding.

4.0 HISTORY OF ANTI-LOCK BRAKING SYSTEM

4.1 WHEN ANTI-LOCK BRAKING SYSTEM IS FOUND

1936 – Bosch and Mercedes-Benz partner – R & D into ABS.

1972 – WABCO partners with Mercedes-Benz developing first ABS for trucks.

1978 – First production-line installation of ABS into Mercedes and BMW

vehicles.

1981 – 100,000 Bosch ABS installed.

1936 – German company Bosch is awarded a patent for ‘Apparatus for preventing

lock-braking of wheels’

1985 – First ABS installed on US vehicles.

1986 – 1M Bosch ABS installed.

1987 – Traction comtrol – in conjuction with ABS – used on passenger vehicles

1989 – ABS hydraulic unit combined with standard hydraulic brake unit.

1992 – 10M Bosch ABS installed.

1995 – Electronic Stability – in conjunction with ABS and TCS – for passener

cars.

1999 – 50M Bosch ABS installed.

2000 – 6 of 10 new cars on the road are ABS equipped.

2003 – 100M Bosch ABS installed.

5.0 HOW ANTI-LOCK BRAKING SYSTEM WORK

Figure5.0

Basically, thereare sensors at each of the four wheels (or in the case of the less

sophisticated three-channel system, one on each of the fronts and only one for the pair of rears ).

These sensors watch the rotation of the wheels. When any one of the wheels stops rotating due to

too much brake application, the sensors tell the car’s computer, which then releases some of the

brake line pressure that you’ve applied – allowing the wheel to turn again. Then, just as fast as it

released the pressure, the computer allows the pressure to be applied again which stops the

rotation of the wheel again. Then it releases it again and so on. With most ABS, this releasing

and re-application or pulsing of the brake pressure happens 20 or more time per second.

If the ECU detecs awheel turning significantly faster than the others, brake hydraulic

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

This process is repeated continuously and can be detected by the driver via brake pedal pulsation.

Some ati-lock system can apply or release braking pressure 16 times pr second.

The ECU is programmed to disregard differences in wheel rotative speed below a critical

threshold, because when the car is turning, the two wheels towards the centre of the curve turn

slower than the outer two. For this same reason, a differential is used in virtually all roadgoing

vehicles.

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

vehicle instrument panel, and the ABS will be disabled until the fault is rectified.

The modern ABS applies individual brake pressure to all four wheels through a control

system of hub-mounted sensors and a dedicated micro-controller. ABS is offered or comes

standard on most road vehicles produced today and is the foundation for ESC systems, which are

rapidly increasing in popularity due to the vast reduction in price of vehicle electronics over the

years.

Modern electronic stability control (ESC or ESP) systems are an evolution of the ABS

concept. Here, a minimum of two additional sensors are added to help th system work, these are

steering wheel angle sensors and a gyroscopic sensor. The theory of operation is simple, when

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

steering wheel sensor report, the ESC software will brake the necessary individual wheels.

6.0 COMPONENTS IN ANTI_LOCK BRAKING SYSTEM

Figure 6.0

6.1 ANTI-LOCK BRAKING SYSTEM CONSIST OF 4 PRIMARY

COMPONENTS:

1. ABS CONTROLLER

- The brains of the system. ABS Controllers are a computer that reads the inputs and

then controls the system to keep the wheels from locking up and skidding.

2. ABS SPEED SENSORS

- There are generally one on each wheel (sometimes they are located on the

differential). It detects a change in acceleration in the longitudinal direction of the

vehicle and outputs it to the ABSCM as a voltage signal.

3. ABS MODULATOR / VALVES

- Some system have separate valves for each wheel with modulator to control them.

Other systems they are combined. In either case they work with the controller and the

pump to individual wheels brakes to control the braking.

4. ABS PUMP

- Since the ABS modulator/ valves can release pressure from the individual wheels

brakes there needs to be a way to restore the pressure when required. That is what the

ABS pumps job my experience a slight pedal vibration. This cycling is happen many

times per second and this slight vibration is natural.

7.0 TYPES OF ANTI-LOCK BRAKING SYSTEM

Anti-lock braking systems use different schemes depending on the type of brakes in use.

They can be differentiated by the number of channels: that is, how many valves that are

individually controlled—and the number of speed sensors.

7.1 Four-channel, four-sensor ABS

This is the best scheme. There is a speed sensor on all four wheels and a separate

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

to make sure it is achieving maximum braking force.

7.2 Three-channel, four-sensor ABS

There 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. Older vehicles with four-

wheel ABS usually use this type.

7.3 Three-channel, three-sensor ABS

This 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. The speed sensor for the rear wheels is located in the rear axle. This

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

maximum braking force. The rear wheels, however, are monitored together; they both

have to start to lock up before the ABS will activate on the rear. With this system, it is

possible that one of the rear wheels will lock during a stop, reducing brake effectiveness.

This system is easy to identify, as there are no individual speed sensors for the rear

wheels.

7.4 Two-channel, four sensor ABS

This system, commonly found on passenger cars from the late '80s through early

2000s (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.

7.5 One-channel, one-sensor ABS

This 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 axle.

This system operates the same as the rear end of a three-channel system. The 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

effectiveness. This system is also easy to identify, as there are no individual speed

sensors for any of the wheels.

8.0 EFFECTIVENESS

A 2004 Australian study by Monash University Accident Research Centre found that

ABS:[1]

Reduced the risk of multiple vehicle crashes by 18 percent,

Decreased the risk of run-off-road crashes by 35 percent.

On high-traction surfaces such as bitumen, or concrete, many (though not all) ABS-equipped

cars are able to attain braking distances better (i.e. shorter) than those that would be possible

without the benefit of ABS. In real world conditions, even an alert and experienced driver

without ABS would find it difficult to match or improve on the performance of a typical driver

with a modern ABS-equipped vehicle. ABS reduces chances of crashing, and/or the severity of

impact. The recommended technique for non-expert drivers in an ABS-equipped car, in a typical

full-braking emergency, is to press the brake pedal as firmly as possible and, where appropriate,

to steer around obstructions. In such situations, ABS will significantly reduce the chances of a

skid and subsequent loss of control.

In gravel, sand and deep snow, ABS tends to increase braking distances. On these surfaces,

locked wheels dig in and stop the vehicle more quickly. ABS prevents this from occurring. Some

ABS calibrations reduce this problem by slowing the cycling time, thus letting the wheels

repeatedly briefly lock and unlock. Some vehicle manufacturers provide an "off-road" button to

turn ABS function off. The primary benefit of ABS on such surfaces is to increase the ability of

the driver to maintain control of the car rather than go into a skid, though loss of control remains

more likely on soft surfaces such as gravel or on slippery surfaces such as snow or ice. On a very

slippery surface such as sheet ice or gravel, it is possible to lock multiple wheels at once, and this

can defeat ABS (which relies on comparing all four wheels, and detecting individual wheels

skidding). Availability of ABS relieves most drivers from learning threshold braking.

A June 1999 National Highway Traffic Safety Administration (NHTSA) study found that ABS

increased stopping distances on loose gravel by an average of 27.2 percent.

According to the NHTSA,

"ABS works with your regular braking system by automatically pumping them. In vehicles not

equipped with ABS, the driver has to manually pump the brakes to prevent wheel lockup. In

vehicles equipped with ABS, your foot should remain firmly planted on the brake pedal, while

ABS pumps the brakes for you so you can concentrate on steering to safety."

When activated, some earlier ABS systems caused the brake pedal to pulse noticeably. As most

drivers rarely or do not brake hard enough to cause brake lock-up, and drivers typically do not

read the vehicle's owners manual, this may not be noticeable until an emergency. Some

manufacturers have therefore implemented a brake assist system that determines that the driver is

attempting a "panic stop" (by detecting that the brake pedal was depressed very fast, unlike a

normal stop where the pedal pressure would usually be gradually increased, Some systems

additionally monitor the rate at the accelerator was released)[citation needed] and the system

automatically increases braking force where not enough pressure is applied. Hard or panic

braking on bumpy surfaces, because of the bumps causing the speed of the wheel(s) to become

erratic may also trigger the ABS. Nevertheless, ABS significantly improves safety and control

for drivers in most on-road situations.

Anti-lock brakes are the subject of some experiments centred around risk compensationtheory,

which asserts that drivers adapt to the safety benefit of ABS by driving more aggressively. In

a Munich study, half a fleet of taxicabs was equipped with anti-lock brakes, while the other half

had conventional brake systems. The crash rate was substantially the same for both types of cab,

and Wilde concludes this was due to drivers of ABS-equipped cabs taking more risks, assuming

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.

The Insurance Institute for Highway Safety released a study in 2010 that found motorcycles with

ABS 37% less likely to be involved in a fatal crash than models without ABS.

9.0 ADVANTAGES & DISADVANTAGES

9.1 ADVANTAGES

1. It allows the driver to maintain directional stability and control over steering

during braking.

2. Safe and effective

3. Automatically changes to brake fluid pressure at each wheel to maintain optimum

brake performance.

4. ABS absorbs the unwanted turbulance shock waves and modulates the pulses thus

permitting the wheel to continue turning under maximum braking pressure.

9.2 DISADVANTAGES

1. Stop Timed - Anti-lock brakes are made to provide for surer braking in slippery

conditions.

2. Delicate Systems – It’s easy to cause a problem in a ABS system by messing

around with the brakes. Problems include disorientation of the ABS system, where a

compensating brake sensor causes the vehicle to shudder, make loud noise or genarally brake

worse.

3. Cost – An ABS can be expensive to maintain. Expensive sensors on each wheel

can cost hundreds of dollars to fix if they get out of calibration or develop other problems.

4. System damage – A variety of factors can cause the system to be less effective,

and can present with everything from shuddering of vehicle to loud noises while trying to stop.

10.0 COMPARISON

Anti-lock braking system

The advantages of ABS brakes (anti-lock braking system), are just as the meaning of

their acronym implies, they eliminate or greatly reduce the possibility of brake lock up and

therefore provide a better chance of steering out of trouble. 

ABS brakes were designed to combat the problem of tire lock up and uncontrolled spins. Since

brakes are most effective at slowing the car at a point just before wheel lock up, a system that

provides for wheel braking while preventing wheel lock up is very desirable. 

Anti-lock brakes do just this by using a computer processor to monitor and control the

application of the brakes. At braking, the processor monitors rpm and braking pressure on each

of the vehicle's wheels. With this information, measured amounts of pressure are sent to each

wheel in the form of hydraulic pulses of pressure to the calipers. These pulses achieve the

desired braking pressure without allowing the wheels to lock up. 

Hydraulic braking system

Conventional hydraulic brakes work by using a cylinder (actuator), which squeezes brake

calipers together around the wheel's rotor when the brake petal is depressed. Difficulties arise

with these conventional brakes if the road is slick and the driver executes a panic stop. Under

these conditions the wheels may lock up and the tires run the risk of losing their grip. When tires

lose their grip of the road, there is a good chance that the car may go into an uncontrolled spin.

This is why drivers in older vehicles have been taught in the past to pump brakes when on icy

roads. 

EBD (Electronic brake – force distribution system)

Electronic brake- force distribution system also called as Electronic brake-force

limitation is an automobile brake technology that automatically varies the amount of force

applied to each of a vehicle’s brakes, based on road conditions, speed, loading, etc.

EBD system is  always coupled with anti-lock brake-force system. The most important function

of EBD is to maintain vehicular control with variation in braking pressure applied to each wheel

in order to maximize stopping power.

Pumping brakes

Pumping brakes are used when a pump is included in part of the vehicle.  These types of

brakes use an internal combustion piston motor to shut off the fuel supply, in turn causing

internal pumping losses to the engine, which causes braking.

Servo brakes

Servo brakes are found on most cars and are intended to augment the amount of pressure

the driver applies to the brake pedal.  These brakes use a vacuum in the inlet manifold to

generate extra pressure needed to create braking.  Additionally, these braking systems are only

effective while the engine is still running.

In some vehicles we may find that there are more than one of these braking systems included.

These systems can be used in unison to create a more reliable and stronger braking system. 

Unfortunately, on occasion, these braking systems may fail resulting in automobile accidents and

injuries.

Advanced Emergency Braking system (AEBS)

An Advanced Emergency Braking System (AEBS) or Autonomous Emergency

Braking (AEB) is an autonomous road vehicle safety system which employs sensors to monitor

the proximity of vehicles in front and detects situations where the relative speed and distance

between the host and target vehicles suggest that a collision is imminent. In such a situation,

emergency braking can be automatically applied to avoid the collision or at least to mitigate its

effects. United Nations Economic Commission for Europe (UNECE) has announced that this

kind of system will become mandatory for new heavy vehicles starting in 2015. A recent study

suggests that if all cars feature the system, it will reduce accidents by up to 27 percent and save

up to 8000 lives per year.

Emergency brake assist (EBA)

Emergency brake assist (EBA) or Brake Assist (BA or BAS) is a generic term for

anautomobile braking technology that increases braking pressure in an emergency situation. The

first application was developed jointly by Daimler-Benz andTRW/LucasVarity. Research

conducted in 1992 at the Mercedes-Benz driving simulator in Berlin revealed that more than

90% of drivers fail to brake with enough force in emergency situations.

By interpreting the speed and force with which the brake pedal is pushed, the system detects if

the driver is trying to execute an emergency stop, and if the brake pedal is not fully applied, the

system overrides and fully applies the brakes until the Anti-lock Braking System (ABS) takes

over to stop the wheels locking up.

11.0 CONCLUSION

Statistics show that approximately 40% of automobilr accidents are due to skidding.

These problems commonly occur on vehicle with conventional brake system which can be

avoided by adding devices called ABS. If there is an ABS failure, the system will revert to

normal brake operation. Normally the ABS warning light will turn on and let the driver know

there is a fault.

12.0 REFERENCES

Anti-lock braking system research (April 07,2012)

http://www.slideshare.net/jyotigangar/antilock-braking-system-report

Anti-lock braking system( February 04,2011) http://en.wikipedia.org/wiki/Anti-

lock_braking_system

Anti-lock braking system prepared by Eng.Haitham Shehata Hussein ( Jun 14,2014)

http://www.slideshare.net/haithamshehata/anti-lock-abs-show-35862387