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?
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
Components of ABS System
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
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
Deceleration Sensor
Basic Operation
• The LED’s are On when the ignition switch is
• 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
• 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
• The sensor converts the force into
electric signal