Coriolis Vibrational Gyroscope

Fundamental concept
Particle moving  through a slot on a rotating platform. The Coriolis component of acceleration produces a normal force, N, on the particle due to the motion within the rotating reference frame of the platform. The magnitude of this contact force is proportional to  the product of the relative velocity vrel and the rotation rate ω of the platform. The side of the particle on which the normal force acts depends on the sign of this same product of vrel and ω.

Application
This concept is used in Coriolis vibrational gyroscopes (CVG's) to measure the orientation angle of a rotated phone. In CVG's, the radial motion vrel is produced by exciting the contacting particle into oscillations. From the measured vrel and contact force N, the rotation rate ω can be calculated. An integration of ω then produces the rotation angle of the platform.

For the particular application of CVG's in cell phones, the oscillating mass is actually the vibrations of MEMS-sized beams along a radial line of the rotating phone. The vibrational motion  transverse to excited beam motion can then be used to determine the Coriolis component of acceleration, and therefore ω.