Anti Lock Breaking System

Adnan AslamB.Sc Mechanical EngineeringHITEC University Taxila, Pakistan

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CONTENTS

What is ABS?Why we need it?Block DiagramComponents of ABSTypes of ABS SystemsHow does it WorksComparison of ABS Vs. Non ABS Vehicle(video)Pros and Cons Conclusion

WHAT IS ABS?

Antilock braking systems are electronic systems that monitor and control wheel slip during vehicle braking.ABSs can improve vehicle control during braking, and reduce stopping distances.Reducing wheel slip improves vehicle stability and control during braking.

December 9, 20153http://www.a1autothreebroscarrepair.com/services.asp?service=1232

MOTIVATION FOR ABS

Under hard braking, an ideal braking system should provide:

The shortest stopping distances on all surfaces

Maintain vehicle stability and steer-ability

Anti-lock braking systems were developed to best meet these needs.

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December 9, 20155 MOTIVATION FOR ABS

SYSTEM DIAGRAM

December 9, 20156http://www.slideshare.net/haithamshehata/anti-lock-abs-show-35862387

ABS COMPONENTS OVERVIEW

Wheel Speed Sensors (up to 4)

Electronic Control Unit (ECU)

Brake Master Cylinder, Hydraulic Modulator Unit with Pump and Valves

Vehicles Physical Brakes

December 9, 20157http://aermech.com/anti-lock-braking-system-abs-working/

December 9, 20158ABS COMPONENTS OVERVIEW

WHEEL SPEED SENSOR (WSS)

It is mounted near the toothed ring.

Teeth on the sensor ring rotate past the magnetic sensor, causing a reversal of the magnetic field polarity, resulting in a signal with frequency related to the angular velocity of the axle.

December 9, 20159http://www.aa1car.com/library/diagnosing_abs_wheels_speed_sensors.htm

HYDRAULIC MODULATOR UNIT

The hydraulic modulator unit contains the ABS pump as well as solenoid valves for each brake line. The fifth line - far right - is from the brake master cylinder, which is connected to the brake pedal.

December 9, 201510http://www.aa1car.com/library/abs_bleeding.htm

VALVES AND BRAKES

The valves modulate the brake pressure up to 20 times per second, effectively realizing the ideal tire slip percentage.

ABS pumps the brakes much faster than any driver could.

December 9, 201511http://autorepair.about.com/cs/generalinfo/l/bldef_001.htm

TYPES OF ANTI-LOCK BRAKING SYSTEMFour channel, four sensor ABS: This is the best scheme, there is speed sensor on all four wheels and a separate valve for all the four wheels.Three channel, three sensor ABS: This scheme is commonly found on pick up trucks with four wheels ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. One channel, one sensor ABS: it has one valve ,which controls both rear wheels , and one speed sensor, located in the rear axle.

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4 SENSORS 3 SENSORS1 SENSORDecember 9, 201513

How does ABS work.?Sensors at each of the four wheels Sense the rotation of the wheel. Too much brake application Wheel stop rotating Sensors ECU Releases brake line pressure Wheel turns again. Then ECU applies pressure again Stops the rotation of the wheel releases it again and so on This releasing and re-application or pulsing of brake pressure happens 20-30 times per second or more.This keeps the wheel just at the limit before locking up and skidding no matter

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December 9, 201515How does ABS work.?

ADVANTAGES

It can be used for reducing the stopping distance.It enables to steer while the brakes are firmly applied.It allows braking firmly on surfaces with different level of grips.Safe & Effective

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DISADVANTAGES

Drivers may take more risks when driving with vehicles fitted with ABS.

People who are inexperienced in using ABS may respond inappropriately when they activate the system.

Maintenance of a Car equipped with ABS is required more.Very Costly

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CONLUSION

Approximately 40 % of automobile 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. You have to understand that ABS does not raise the speed limits of your vehicle. It only helps you stay within the limits. ABS does not allow you to drive faster, brake later.

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