Anti-Lock Braking System
Below is an overview of this system's operation
Anti-lock Brake Systems (ABS)
Originally developed for aircraft, ABS basically works by limiting the pressure
to any wheel which decelerates too rapidly. This allows maximum stopping force to be applied
without brake lockup (skidding). If standard brakes are applied too hard, the wheels "lock"
or skid, which prevents them from giving directional control. If directional control (steering)
is lost, the vehicle skids in a straight line wherever it is going. ABS allows the driver to
steer during hard braking, which allows you to control the car much better. In the old days,
drivers had to know how to "pump" the brakes or sense the lockup and release foot
pressure in order to prevent skidding. This meant that if only one wheel lost traction and
started to skid, the driver would have to reduce braking force to prevent a skid. The advantage
of ABS is that the brakes on the wheels with good traction can be used to the fullest possible
amount, even if other wheels lose traction.
In operation, the wheelspeed sensors at each wheel send electronic pulse
signals to the control unit. If wheel lockup (rapid deceleration) is detected during brake
application, the computer signals the valve unit to limit the hydraulic pressure to the wheel
cylinder. This is usually accomplished by diverting the fluid into a small reservoir. The fluid
is later pumped out of the reservoir and returned to the main fluid reservoir when the brakes
are not being applied.
The anti-lock brake system tests itself every time the vehicle is started
and every time the brakes are applied. The system evaluates its own signals. If a defect is
detected, the system then turns off, leaving normal braking unaffected.
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