Sensors used in ABS (Anti

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Transcript Sensors used in ABS (Anti

Sensors used in ABS
(Anti-Lock Braking System)
Dr. Shahin H. Berisha
GateWay Community College
Phoenix, Arizona, USA
What is ABS?
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ABS provides safety
Prevent the wheels from locking
Maintain directional stability
ABS controls each front brake separately and
the rear brakes as a pair
• ABS helps to stop a car in shortest possible
distance without locking the wheel and
maintaining directional control (Fig. on page 119)
Basic Operation of ABS
• Four wheel ABS use a speed sensor at each
wheel, (slide)
• Signal voltage from these sensors is
connected to ECU,
• In rapid braking each sensor detect change in
speed and send signal to ABS ECU,
• Based on this information the ABS ECU
calculates necessary parameters and then
provides optimum braking pressure on each
wheel.
Components of ABS System
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Speed Sensors monitor wheel speed,
G - Sensor monitors rate of acceleration,
ABS Actuators control brake system pressure,
Control Relay controls Actuator Pump Motor
and Solenoids,
• ABS ECU monitors sensor inputs and controls
the Actuator,
• ABS Warning Lamp alerts driver to system
conditions. (Fig. On page 125)
Wheel Speed Sensors
Basic Operation
• This sensor is an electromagnet in which a ac
voltage is induced into the coil (Figure on page 127),
• As the sensor rotor rotates it induces the
voltage in the coil of electromagnet,
• As the rotation of the sensor rotor increases,
the magnitude and the frequency of induced
voltage increases,
• The induced voltage is information feed into
ABS ECU.
Deceleration Sensor
• This sensor measures the car’s rate of
deceleration to improve braking performance,
• Deceleration sensor is used on all full-time 4WD
• The deceleration sensor senses the vehicle’s rate
of deceleration and sends signal to the ABS ECU.
• The ECU compares the rate of deceleration and
vehicle speed to determine the precise road
surface condition and takes appropriate control
measures.
Deceleration Sensor
Basic Operation
• The LED’s are On when the ignition switch is
ON
• When the vehicle’s rate of deceleration
changes, the split plate swings in the vehicle’s
rear-to-front direction.
• The slits in the slit plate act to expose the
light from the LEDs to the phototransistors.
• This movement of slit plate switches the
phototransistors ON and OFF. (Figure on page 128)
Semi-Conductor Deceleration
Sensor
• Introduced in 1996 Toyota RAV4
• Consist of two semiconductor sensors
• Each semiconductor is provided with a
mass which exerts pressure based on
the deceleration force applied on the
vehicle
• The sensor converts the force into
electric signal