ANTI-LOCK BRAKES

ANTI-LOCK ANTI-LOCK BRAKESBRAKES

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ANTI LOCK BRAKINGANTI LOCK BRAKING SYSTEMSYSTEM

BYUDDIPTA RANJAN SARMAH (0804104)SYED JAVED IFTIKAR AHMED (0804113)RITURAJ DHAR (0804116)

IntroductionIntroduction Wheel lockup during braking causes skidding Wheel lockup during braking causes skidding

which in turn cause a loss of traction and which in turn cause a loss of traction and vehicle control vehicle control

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

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

Concept of ABSConcept of ABS A A skidding wheelskidding wheel (where the tire contact (where the tire contact

patch is sliding relative to the road) has less patch is sliding relative to the road) has less tractiontraction than a non-skidding wheel than a non-skidding wheel

By keeping the wheels from skidding while By keeping the wheels from skidding while you slow down, anti-lock brakes benefit you in you slow down, anti-lock brakes benefit you in two ways: two ways:

You'll stop faster, and you'll be able to steer You'll stop faster, and you'll be able to steer while you stop while you stop

ComparisonComparison

ANTI-LOCK BRAKESANTI-LOCK BRAKES

Computerized ABS is Computerized ABS is designed to keep the designed to keep the wheels from locking as wheels from locking as the brakes are applied. the brakes are applied.

A locked wheel A locked wheel provides very little or provides very little or no directional control. no directional control.


The following slides show the common ABS The following slides show the common ABS components. components.

Some components are part of both the Some components are part of both the conventional and ABS system.conventional and ABS system.


When operating a vehicle with ABS never When operating a vehicle with ABS never pump the brakes. pump the brakes.

Doing so will make the ABS system Doing so will make the ABS system ineffective. ineffective.

Always apply firm pressure.Always apply firm pressure.


Drivers may experience a pulsation in the Drivers may experience a pulsation in the brake pedal, or pedal kick back during an ABS brake pedal, or pedal kick back during an ABS stop. This is normal and not to be confused stop. This is normal and not to be confused with a conventional brake pedal pulsation with a conventional brake pedal pulsation


Anti-Lock

Brake Module

Speed

Sensor

Pressure Valve Dump/Vent Valve

Master Cylinder Assembly

Anti Lock

12 V


Major components of the anti-lock brake Major components of the anti-lock brake system consist of a system consist of a Brake control module,Brake control module, Solenoid valve assembly,Solenoid valve assembly, Speed sensor's Speed sensor's Wiring, and the amber ABS brake warning light. Wiring, and the amber ABS brake warning light.


Brake Control ModuleBrake Control Module: : The brake control module is a compute that The brake control module is a compute that

receives information from the speed sensor receives information from the speed sensor and compares it to the speed of other wheels. and compares it to the speed of other wheels.

When one wheel is approaching lock-up When one wheel is approaching lock-up pressure can be vented allowing the wheel pressure can be vented allowing the wheel nearing lock-up to speed up. nearing lock-up to speed up.


If a wheel is to fast pressure can be increased If a wheel is to fast pressure can be increased to slow down the wheel. to slow down the wheel.

If both wheel are approximately the same If both wheel are approximately the same speed the brake control module can enter a speed the brake control module can enter a pressure hold mode of operation. pressure hold mode of operation.


Solenoid Valve Assembly: Solenoid Valve Assembly: Is a pair of valves that can:Is a pair of valves that can:

A.A. Increase pressure Increase pressureB.B. Hold pressure steady Hold pressure steady C.C. Decrease pressure Decrease pressure


During pressure increase mode of operation fluid is allowed to flow through both solenoids to the brake caliper

Solenoid 1

Pressure increase

Solenoid 2

Pressure decrease/Vent solenoid

Brake line under pressure

Brake fluid line not under pressure

ANTI-LOCK BRAKESANTI-LOCK BRAKESDuring Pressure Hold mode of operation both solenoids are closed and no additional fluid is allowed to flow to brake calipers.

Solenoid 1

Pressure increase

Solenoid 2

Pressure decrease/Vent

ANTI-LOCK BRAKESANTI-LOCK BRAKESDuring Pressure Vent mode the pressure increase solenoid is closed. The Vent solenoid opens allowing fluid to vent into an accumulator chamber

Solenoid 1

Pressure increase

Solenoid 2

Pressure decrease/Vent


ABS system can maintain extremely high ABS system can maintain extremely high static pressure and must be disabled before static pressure and must be disabled before attempting repairs. attempting repairs.

Normally pumping brake 20-30 times will Normally pumping brake 20-30 times will release pressure. release pressure.


ABS brake system are ABS brake system are Integrated Integrated NonintegratedNonintegrated


An integrated system has the master cylinder An integrated system has the master cylinder and control valve assembly made together.and control valve assembly made together.

A nonintegrated has the master cylinder and A nonintegrated has the master cylinder and control valve assembly made separate. control valve assembly made separate.


ABS operates using the same hydraulic ABS operates using the same hydraulic principal as conventional brakes.principal as conventional brakes.

ABS system only operates when wheel lock-ABS system only operates when wheel lock-up is emanate. up is emanate.

A bussing noise and bakes pedal vibration is A bussing noise and bakes pedal vibration is normal during ABS operation. normal during ABS operation.


To determine if wheel To determine if wheel lock-up is about to lock-up is about to occur vehicles a wheel occur vehicles a wheel speed sensor.speed sensor.


There 3 ABS There 3 ABS configurations configurations 1. channel normally 1. channel normally

RWAL (rear wheel anti-RWAL (rear wheel anti-lock)lock)

In a one channel RWAL In a one channel RWAL system the rear wheels system the rear wheels are controlled togetherare controlled together


ABS brakes are either ABS brakes are either 1. Channel1. Channel 3 Channel3 Channel 4 Channel4 Channel


1 channel ABS system controls the 1 channel ABS system controls the rear wheel rear wheel together. together.

A 1 channel system only has 1 speed sensor A 1 channel system only has 1 speed sensor and control valve assembly. and control valve assembly.


A three (3) channel ABS system control the A three (3) channel ABS system control the rear wheel togetherrear wheel together and the and the front front independentlyindependently. .

Three channel ABS system have Three channel ABS system have 3 speed3 speed sensor and one (1) control modulesensor and one (1) control module


Wheel SlippageWheel Slippage, is the wheel speed in relation , is the wheel speed in relation to vehicle speed.to vehicle speed.

If vehicle speed is faster than the wheel speed If vehicle speed is faster than the wheel speed slippage is negative. And the wheel may slippage is negative. And the wheel may become lock-upbecome lock-up


If vehicle speed is slower than wheel speed. If vehicle speed is slower than wheel speed. Wheel slippage is positive. Wheel slippage is positive.

Positive wheel slippage occurs when a wheel Positive wheel slippage occurs when a wheel is spinning. is spinning.

NOTE:NOTE: Late model vehicles use the same Late model vehicles use the same ABS components with traction control. ABS components with traction control. Traction control prevent a vehicle from Traction control prevent a vehicle from spinning out of control. spinning out of control.


The best braking action occurs at between 10-The best braking action occurs at between 10-20%. 20%.

If vehicle speed and wheel speed is the same If vehicle speed and wheel speed is the same wheel slippage is 0%wheel slippage is 0%

A lock-up wheel will have a wheel slippage of A lock-up wheel will have a wheel slippage of 100%100%


In a diagonally split In a diagonally split system brake system the system brake system the left frontleft front and and right rearright rear brakes are controlled brakes are controlled together. together.

Diagonally split systems Diagonally split systems offer an added safety offer an added safety value. value.

Master

Cylinder

AdvantagesAdvantages It allows the driver to maintain directional stability It allows the driver to maintain directional stability

and control over steering during brakingand control over steering during braking Safe and effectiveSafe and effective Automatically changes the brake fluid pressure at Automatically changes the brake fluid pressure at

each wheel to maintain optimum brake performance.each wheel to maintain optimum brake performance. ABS absorbs the unwanted turbulence shock waves ABS absorbs the unwanted turbulence shock waves

and modulates the pulses thus permitting the wheel to and modulates the pulses thus permitting the wheel to continue turning under maximum braking pressure.continue turning under maximum braking pressure.

DisadvantagesDisadvantages

It is very costlyIt is very costly Maintenance cost of a car equipped with ABS Maintenance cost of a car equipped with ABS

is more.is more.

ConclusionConclusion Statistics show that approximately 40 % of Statistics show that approximately 40 % of

automobile accidents are due to skidding. automobile accidents are due to skidding. These problems commonly occur on vehicle These problems commonly occur on vehicle

with conventional brake system which can be with conventional brake system which can be avoided by adding devices called ABSavoided by adding devices called ABS

If there is an ABS failure, the system will If there is an ABS failure, the system will revert to normal brake operation. Normally the revert to normal brake operation. Normally the ABS warning light will turn on and let the ABS warning light will turn on and let the driver know there is a fault driver know there is a fault

ANTI-LOCK BRAKES

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