Anti-Lock Braking Sensors The role of the ABS is to control the
wheel speed in order to prevent the wheels from locking and to
assure a maximum braking force. This is of major importance when
the runway is slippery or very short. Wheel moment of inertia,
Rotational wheel speed, Friction coefficient, Wheel Radius
Normal force per wheel Friction force, Aircraft speed Figure 1b:
are analogous to the above vehicle wheel shown. Forces acting on
a braked wheel are shown in fig1b.The ABS commands the brake
pressure as a function of the difference between the measured
and the reference wheel speed. The latter is calculated from the
measured aircraft speed and the desired wheel slips, using
equation. At the moment, when the pilot pushes the brake pedal
the brake pressure and the wheel slip increase provoking a
ground force between tyre and runway. Assuming the case of full
braking, the ABS will control the wheel speed to its reference
value. To achieve a maximum braking force the reference slip
should be chosen close