Audi Q7 2017 Manual page 12

Measurement of vehicle rotation about the X and Z axes
The sensors for the measurement of vehicle rotation about
the X and Z axes work on the "Coriolis force" principle.
The Coriolis force acts on all bodies that move within a
rotating reference system. The effect of the Coriolis force is
demonstrated in the example given here. A ball is rolled on
a disc. When the disc is stationary the ball rolls straight
across it.
When the disc rotates while the ball is rolling on the plat-
form, however, the ball is deflected opposite the direction
of motion of the disc. The degree of deflection depends on
the rotational speed of the disc.
The sensor consists of a micromechanical body which is
permanently subjected to oscillation excitation.
When the vehicle turns, the direction of movement of the
oscillating body changes. These deflections relative to the
direction of movement (changes in movement) are pro-
cessed digitally and evaluated accordingly.
To measure rotation about the X and Z axes, a rollover sensor
(for rollover detection) and an inertial sensor (for ESC signal
indicating yaw rate about Z) are arranged at a 90° offset
relative to each other in Airbag Control Module J234.
8
X
Airbag Control Module J234
Z
637_088
637_016a
637_016b
637_012