Antilock brake systems (ABS), an excellent safety feature,
are rapidly becoming standard on today’s automobiles. The ABS system
consists of two subsystems:
- The hydraulic system, consisting of the master cylinder, calipers,
wheel cylinders, pads, shoes and associated connecting valves, lines
and hoses, as in a conventional brake system.
- The ABS controller (computer), its associated sensors (INPUTS), actuators
(OUTPUTS), required wiring and connectors.
The computer receives signals from the individual wheel sensors regarding
the speed of each wheel. It then compares the speed of each wheel with that
of the others. If that comparison indicates wheel lockup is present, appropriate
signals are sent to the various valves and actuators to raise or lower hydraulic
pressure to the individual wheels to correct the skid. This action is repeated
thousands of times per second, producing maximum stopping ability under
all conditions. All of this activity goes unnoticed by the driver unless
a component fault is detected by the computer and the “BRAKE”
or “ABS” warning lights are illuminated on the dashboard.
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