ANTILOCK BRAKINH SYSTEM, LE THANH PHUC

Wheel Speed Sensor6 A wheel speed sensor is mounted at each wheel and sends a wheel rotation signal to the ABS ECU... • The actuator controls hydraulic brake pressure to each disc brakec

ANTILOCK BRAKING SYSTEM

Le Thanh Phuc

Faculty of Automotive Engineering

University of Technical Education Ho Chi Minh City

Email: phuclt@hcmute.edu.vn

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ABS system diagram

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Fundamental ABS system

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Wheel Speed Sensor

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A wheel speed sensor is mounted at each wheel and sends a wheel rotation signal to the ABS ECU

• The actuator controls hydraulic brake pressure to each disc brakecaliper or wheel cylinder based on input from the system sensors,thereby controlling wheel speed

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Pressure Holding Valve (2-position valve)

Pressure Reduction Valve (2-position valve)

Normal Braking Mode (2-position valve)

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Pressure Holding Mode (2-position valve)

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Pressure Reduction Mode (2-position valve)

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Pressure Increase Mode (2-position valve)

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ABS wiring diagram

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The ECU judges the slip condition between the wheels

and the road surface by monitoring the change in the

wheel's rotational speed

during braking The ECU controls the ABS actuator to

deliver the

optimum hydraulic pressure to the brake cylinder to

precisely control the speed of the wheels, maintaining

maximum brake force with a 10 to 30% slip ratio

Wheel speed control

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The ECU continuously receives wheel speed

signals from the speed

sensors and deceleration sensor By calculating

the speed and deceleration of each wheel, the

ECU estimates the vehicle speed

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Slip ratio

• The car is traveling at a speed U and the wheels are rotating at an angular speed ωw where

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and where RPMw is the RPM of the wheel in revolutions per minute When the wheel is rolling (no applied brakes)

where rw is the tire effective radius