PHASE INSENSITIVE QUADRATURE NULLING METHOD AND APPARATUS FOR CORIOLIS ANGULAR RATE SENSORS

摘要

Quadrature error occurs in Corolis based vibrating rate sensors because of manufacturing flaws that permit the sensing element to oscillate either linearly along or angularly about an axis that is not orthogonal to the output axis. This creates an oscillation along or about the output axis that is a component of the sensing element's vibration acceleration. This output axis oscillation is in phase with the driven acceleration of the sensing element and is called quadrature error since it is ninety degrees out of phase with the angular rate induced Coriolis acceleration. Rather than applying forces that reorient the axis of the driven vibration to be orthogonal to the output axis to eliminate the output axis oscillation, the present invention applies sinusoidal forces to the sensing element by means of a quadrature servo to cancel the output oscillation. In order to avoid the phase uncertainty associated with electronic modulation, the quadrature servo feeds back a DC signal that is modulated mechanically by means of an interdigitated variable area electrostatic forcer.