Quadrature compensation technique for vibrating gyroscopes

#1. Field of the Invention

#The present invention relates to an inertial instrument, and more specifically pertains to vibrating gyroscopes.

#2. Description of the Prior Art

#The exact nature of this invention, as well as its objects and advantages will become readily apparent from consideration of the following specification in relation to the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

#FIG. 1 is a perspective view in schematic form of the driven and sensing element of a gyroscope and the quadrature driving electrodes according to the present invention;

#FIG. 2 is a graph showing the effect of the invention on quadrature error;

#The construction of various forms of vibrating gyroscopes produced from silicon wafers is well known. U.S. Pat. No. 5,987,986 granted Nov. 23, 1999 to Stanley F. Wyse, Robert E. Stewart, and Samuel H. Fersht for Navigation Grade Micromachined Rotation Sensor System, and assigned to the same assignee as the present application, is one example. The entire disclosure of U.S. Pat. No. 5,987,986 is incorporated herein by reference as if fully set forth hereat.

#Various techniques of nulling the quadrature error that is created in such gyroscope structures have been tried. One such technique is shown and described in an article entitled Surface Micromachined Z-Axis Vibratory Rate Gyroscope by William A. Clark, Roger T. Howe, and Roberto Horowitz presented at a Solid-State Sensor and Actuator Workshop in Hilton Head, S.C. on June 2-6, 1996.

#The technique proposed in the present application is different and is best illustrated by reference to FIGS. 1, 3 and 4 which shows in schematic form the basic elements of a vibrating gyroscope 11 having a frame 13 that is fixedly attached by convenient means 15 to a moving platform, for example. Within frame 13, a dither driven mass 17 is suspended by flexure beams 19 which are designed to flex about a Z axis 25. Each flexure beam 19 has a certain axial stiffness factor K in the Z direction. Mounted within dither driven mass 17 is a proof mass 21 which is attached to the dither driven mass 17 by flexure beams 23. Flexure beams 23 allow the proof mass 21 to rotate about the Y output axis 31. The dither mass and proof mass combination is the dither mass structure.