Abs

ANTI-LOCK BRAKING SYSTEM

By Yusha Patel & Prasham Panchal

TYME-A

Presentation Outline

What is an Anti-Lock Braking System (ABS) ? Motivation for ABS Development ABS Component Overview ABS Components How Does ABS Works ? ABS Configuration Advantages & Disadvantages Summary References

What is ABS ?

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 (ceasing rotation) and avoiding uncontrolled skidding.

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 tobest meet these needs.

ABS Components Overview

• Typical ABS Components:

Wheel Speed Sensors (up to 4)

Valves

Pump

Electronic Control Unit (ECU)

1) Wheel Speed Sensor (WSS) The ABS needs some way of knowing when a wheel is about to lock up.The speed sensors, which are located at each wheel provides this information.

ABS Components

2) Valves

There is a valve in a brake line of each brake controlled by the ABS . On some systems, the valve has three positions :

In position one, the valve is open, pressure from the master cylinder is passed right through to the brake.

In position two, the valve blocks the line, isolating that brake from the master cylinder.

In position three, the valve releases some of the pressure from the brake.

3) Pump

Since the Valve is able to release some pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does ; when a valve reduces the pressure in a line, the pump is there to get the pressure back up. ABS ‘pumps’ the brakes much faster than any driver could.

Anti-lock brake pump and valves

4) Electronic Control Unit

It’s a computer in the car. The ECU receives information from each individual wheel speed sensor , in turn if a wheel loses traction the signal is sent to the controller , the controller will then limit the brake force and activate the ABS modulator which actuates the valves on and off.

We will discuss how one of the simpler system works.

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 times per second or more.

This keeps the wheel just at the limit before locking up and skidding no matter

how hard you apply the brakes.

How Does ABS works ?

With ABS, all you have to doin an emergency is quickly squeeze the brake pedal as hard as you can and hold it there. Let the system do the finesse work for you.

Anti-lock brake components

ABS Configuration

Depending on the ABS application, there are several typical layouts.

ADVANTAGES DISADVANTAGES

Improves vehicle stabilityRapid deceleration is

efficient Improves cornering of

wheelsAvoids skidding of wheels,

hence increases tires life. Insures vehicle safety

Costly as compared to conventional braking systems.

Braking is inefficient when the ignition is switched off.

Summary

An ABS typically consists of: Up to 4 wheel speed sensors An ABS ECU Pumps and Valves The vehicle’s physical brakes

An ABS is designed to modulate braking pressure to attain the peak coefficient of kinetic friction between tire & road, & avoid total wheel lockup.

An ABS, under hard braking conditions, is designed to reduce stopping distances under most conditions, while maintaining vehicle stability and steer ability.

www.google.com

www.howstuffworks.com

http://en.wikipedia.org/wiki/Anti-lock_braking_system

www.bosch-escential.com

REFERENCES….

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