antilock braking systemm

7/30/2019 antilock braking systemm

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A

REPORT

ON

ANTI-LOCK BRAKING SYSTEM (ABS)

Submitted In Partial Fulfilment of Requirement For Award Of Degree

BACHELOR OF TECHNOLOGY

IN

MECHANICAL ENGINEERING

Submitted To: Submitted By:-

Dr. H.C. Garg Tarun (09162003)

HEAD OF DEPARTMENT (ME) (8th

Semester)

Department Of Mechanical Engineering

Guru Jambheshwar University Of Science & Technology

Hisar (125001)

March,2013


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Introduction

Wheel lockup during braking causes skidding which in turn cause a lossof traction and vehicle control.

This reduces the steering ability to change direction. So the car slips &out of control.

With ABS system, the driver can brake hard, take the evasive action andstill be in control of the vehicle in any road condition at any speed and

under any load.


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Hydraulic Brakes

A simple braking system consists of a master cylinder, and four wheelcylinders.

When the brake pedal is pressed the piston in the master cylinder forcesthe liquid out of the cylinder. This liquid presses the two pistons in the

wheel cylinders outwards. These two pistons push the brake shoes out

words.


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What Is Wheel Slip?

Normal driving will not notice difference

Anti-lock Event

Unrestricted tire rotation is 0% slip Tire locked up is 100% slip When we have 100% slip, the tire loses traction and vehicle motion

changes into heat energy. (Not very effective!)


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ABS

The skidding and lack of control was caused by the locking of wheels.

The release and reapply of the brake pedal will avoid the locking of thewheels which in turn avoid the skidding.

This is exactly what an antilock braking system does.


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Pressure Module

When the brake pedal is pumped or pulsed the pressure is quickly appliedand released at the wheels. This is called pressure modulation. Pressure

modulation works to prevent the wheel locking.

ABS can modulate the pressure to the brake as often as 15 times perseconds.

ABS precisely controls the slip rate of The wheels to ensure maximumgrip force from the tyre and it there by ensures maneuverability and

stability of the vehicle.


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Slip Rate

During ABS operation, the target slip rate can be from 10 to 30%.

0% slip means the wheel is rolling freely, while 100 % means the wheelis fully locked.

A slip rate of 25 % means the velocity of a wheel is 25 % less than that ofa freely rolling wheel at the same vehicle speed.


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Main Components

Speed Sensors

Electrical Control Unit (ECU)

Hydraulic Control Unit (HCU) Accumulator


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Wheel Speed Sensor

Detects rotation of wheel

Permanent magnet type

3 Parts Permanent magnet Coil Yoke

Induces AC voltage varied frequency


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Electrical Control Unit (ECU)

Inputs and Outputs

Some ABS ECUs have dual boards

Controls HCU Full Diagnostics Controls Warning Lights Can control each wheel brake independently. (four channel) Most are

three channel

Mechanical Noises


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Hydraulic Control Unit (HCU)


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Accumulator

Stores high pressure brake fluid from Pump

Supplies high pressure fluid in ABS mode

2800 to 3400 PSI Must bleed before replacement or service


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Pump And Motor

Motor is 12V Electric

Works independently of the base brake system

Pressurizes brake fluid up to 2800 psi. Turns on when ever pressure drops below a predetermined level Some are replaceable seperately


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Advantages

It allows the driver to maintain directional stability and control oversteering during braking

Safe and effective Automatically changes the brake fluid pressure at each wheel to maintain

optimum brake performance.

ABS absorbs the unwanted turbulence shock waves and modulates thepulses thus permitting the wheel to continue turning under maximum

braking pressure.


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Disadvantages

It is very costly

Maintenance cost of a car equipped with ABS is more.


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Conclusion

Statistics show that approximately 40 % of automobile accidents are dueto skidding.

These problems commonly occur on vehicle with conventional brakesystem which can be avoided by adding devices called ABS

If there is an ABS failure, the system will revert to normal brakeoperation. Normally the ABS warning light will turn on and let the driver

know there is a fault

antilock braking systemm

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