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Post on 12-Sep-2014
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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….
THANK YOU