anti braking system(abs)

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Antilock braking system(ABS) areelectronic systems that monitor andcontrol wheel slip during vehicle

braking Reducing wheel slip improves vehiclestability and control during braking ,

since stability increases as wheel slipdecreases

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A simple braking system consists of amaster cylinder, and four wheelcylinders

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

wheel cylinders outwards.These twopistons push the brake shoes outwards

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When the pedal is pressed the primarypiston moves to the left

When it crosses the bypass port theliquid is forced along the pipe lines tothe wheel cylinders

When the pedal is released theprimary piston is moved backwards. Itis the spring , which pushes the pistonback wards

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The skidding and loss of control wascaused by the locking of wheels

The release and reapply of the brake

pedal will avoid the locking of thewheels which in turn avoid theskidding

This is exactly what an antilockbraking system does

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When the brake pedal is pumped or pulsedthe pressure is quickly applied and releasedat the wheels. This is called pressuremodulation. Pressure modulation works to

prevent the wheel locking ABS can modulate the pressure to the brake

as often as 15 times per seconds

ABS precisely controls the slip rate of the

wheels to ensure max grip force from the tireand it there by ensures maneuverability andstability of the vehicle

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During ABS operation, the target sliprate can be from 10 to 30 %

0 % slip means the wheel is rolling

freely, while 100% means the wheel isfully locked

A slip rate of 25 % means the velocity

of a wheel is 25 % less than that of afreely rolling wheel at the samevehicle speed

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1.Accumulator:-An accumulator is used to store hydraulic fluid tomaintain high pressure in the brake system.

2.Antilock Hydraulic Control Valve :-

This assembly controls the release andapplication of the brake system pressure to thewheel brake assemblies .

3.Booster pump:-The booster pump is used to provide

pressurized hydraulic fluid to ABS.

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4.Booster/Master cylinder assembly:-

It is needed to modulate hydraulic pressure in

the wheel circuit during the ABS operations.

5.Fluid accumulator:-

Accumulator temporarily stores brake fluid

that is removed from the wheel brake unitduring ABS cycle.

6.Hydraulic control unit:-The unit may have one pump and one motoror it will have one motor and two pumps.

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7.Main Valve:-This is a two position valve and is open only inthe ABS mode.

8.Modulator unit:-The modulator unit controls the flow ofpressurized brake fluid to the individual wheelcircuits.

9.Solenoid valves:-

The solenoid valves are located in themodulator unit and are electrically operated bysignals from the control module.

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1.ABS control module:-It monitors system operation and controlsantilock function when needed.

2.Brake pedal sensor:-

Its function is to switch on the brake lights toalert other vehicles that the car is slowingdown and/or is going to stop.

3.Wheel speed sensor:-These are generally used for sensing thewheel speed.

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Control of steeringFail-safe electrical/electronic

systemTraction control

ABS has malfunction indicator

lamp

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Increases steering ability and vehiclestability during braking

If the electrical/electronic system fails,

the ABS is shut off It has an optional feature that controlsexcessive wheel spin during

acceleration Informs the driver or technician thatan ABS fault has occurred

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AUTOMATIC STABILITY CONTROL

AUTOMATIC TRACTION CONTROL(ATC)

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Automatic traction control systems applythe brakes when a drive wheel attempts tospin and lose traction.

The system works best when one drivewheel is working on a good traction surfaceand the other is not.

The system also works well when the

vehicle is accelerating on slippery roadsurfaces, especially when climbing hills

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Stability control systems momentarilyapply the brakes at any one wheel tocorrect over steer or under steer.

The control unit receives signals fromthe typical sensors plus a yaw, lateralacceleration (G-force) and a steering

angle sensor

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It allows the driver to maintain directionalstability and control over steering during braking

Safe and effective

Automatically changes the brake fluid pressure ateach wheel to maintain optimum brakeperformance.

ABS absorbs the unwanted turbulence shockwaves and modulates the pulses thus permittingthe wheel to continue turning under maximumbraking pressure

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It is very costly.

Maintenance cost of a carequipped with ABS is more.

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Statistics show that approximately 40 % of

automobile accidents are due to skidding.

These problems commonly occur on vehicle

with conventional brake system which can beavoided by adding devices called ABS.

If there is an ABS failure, the system will

revert to normal brake operation. Normallythe ABS warning light will turn on and let thedriver know there is a fault.

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DOUBTS &DISCUSSION

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BYABHISHEK

HARSANHARSHA

LAXMIDHAR