A silicon membrane gyroscope with electrostatic actuation

Vibrating gyroscopes employing matched primary and secondary natural modes of vibration offer high sensitivities to applied rates of turn. The preferred approach to matching the two modes is, to base the design of the gyroscope on a symmetrical structure which can be fabricated without the need to achieve dimensional accuracy. In the membrane gyroscope, the symmetry of the membrane/inertial pyramidal mass results from the anisotropic bulk etching of silicon with EDP. The primary mode of vibration with angular velocity ω_p is shown. Since the primary motion is at resonance large amplitudes of vibration, i.e. angular velocity, can be achieved with little drive force. The presence of a rate of turn exerts a Coriolis force on the structure which is proportional to the product of the angular velocity of the primary motion and the applied rate of turn. This force excites the secondary mode into vibration with an angular velocity ω_s that is a measure of the rate of turn