Quadrature trim vertical electrodes for yaw axis coriolis vibratory gyroscope
Microelectromechanical systems (MEMS) yaw gyroscopes having out-of-plane quadrature trim electrodes are described. The gyroscope includes a proof mass configured to be driven in-plane. The proof mass includes an opening, or a plurality of openings. The out-of-plane quadrature trim electrodes are positioned to laterally overlap edges of the opening in a projection plane. The out-of-plane quadrature trim electrodes trim in-plane motion of the proof mass in one or two directions to limit quadrature motion. The out-of-plane quadrature trim electrodes may be arranged in a symmetric pattern to enable mode switching.
1 . A microelectromechanical systems (MEMS) gyroscope, comprising:
a substrate;
a proof mass suspended above the substrate and comprising two or more enclosed openings; and
two or more groups of out-of-plane quadrature trim electrodes on the substrate, individual ones of the two or more groups respectively corresponding to individual ones of the two or more enclosed openings, each group including at least one out-of-plane quadrature trim electrode, respective out-of-plane quadrature trim electrodes separated from the proof mass in a direction normal to the proof mass, wherein the out-of-plane quadrature trim electrodes in respective groups are laterally positioned to overlap interior edges of the proof mass at the respective corresponding openings.
2 . The MEMS gyroscope of claim 1 , wherein the proof mass comprises an array of openings and wherein the MEMS gyroscope comprises an array of out-of-plane quadrature trim electrodes laterally positioned to overlap interior edges of corresponding ones of the array of openings.
3 . The MEMS gyroscope of claim 2 , wherein the array of out-of-plane quadrature trim electrodes are arranged in a checkerboard pattern to receive two different voltages.
4 . The MEMS gyroscope of claim 1 , wherein the out-of-plane quadrature trim electrodes are laterally positioned along two dimensions to provide quadrature trim in two in-plane dimensions of the proof mass.
5 . The MEMS gyroscope of claim 1 , further comprising at least one drive electrode configured to drive in-plane motion of the proof mass in a first direction.
6 . The MEMS gyroscope of claim 5 , further comprising a controller configured to apply a direct current (DC) voltage to the out-of-plane quadrature trim electrodes and an alternating current (AC) voltage to the at least one drive electrode.
7 . The MEMS gyroscope of claim 1 , wherein a dimension of each of the out-of-plane quadrature trim electrodes is a value between 20 μm and 40 μm.
8 . The MEMS gyroscope of claim 7 , wherein a dimension of the enclosed opening is a value between 20 μm and 40 μm and a spacing between two adjacent electrodes of the out-of-plane trim electrodes is a value between 0.1 μm and 1.0 μm.
9 . A microelectromechanical systems (MEMS) gyroscope, comprising:
a planar proof mass suspended above a substrate;
drive electrodes in-plane with the planar proof mass and configured to drive in-plane motion of the planar proof mass;
a first pair of out-of-plane quadrature trim electrodes underlying a first opening in the planar proof mass and configured to apply an in-plane quadrature trim force to the planar proof mass at the opening; and
a second pair of out-of-plane quadrature trim electrodes underlying a second opening in the planar proof mass and configured to apply an in-plane quadrature trim force to the planar proof mass at the opening.
10 . The MEMS gyroscope of claim 9 , wherein the planar proof mass comprises an array of openings including the opening and wherein the MEMS gyroscope comprises an array of out-of-plane quadrature trim electrodes including the pair of out-of-plane quadrature trim electrodes, the array of out-of-plane quadrature trim electrodes laterally positioned to overlap interior edges of the array of openings.
11 . The MEMS gyroscope of claim 10 , wherein the array of out-of-plane quadrature trim electrodes are arranged in a checkerboard pattern to receive two different voltages.
12 . The MEMS gyroscope of claim 10 , wherein the array of out-of-plane quadrature trim electrodes are laterally positioned along two dimensions to provide quadrature trim in two in-plane dimensions of the planar proof mass.
13 . The MEMS gyroscope of claim 9 , further comprising a controller configured to apply direct current (DC) voltages to the pair of out-of-plane quadrature trim electrodes and an alternating current (AC) voltage to the drive electrodes.
14 . The MEMS gyroscope of claim 9 , wherein a dimension of each of the out-of-plane quadrature trim electrodes of the pair of out-of-plane quadrature trim electrodes is a value between 20 μm and 40 μm.
15 . The MEMS gyroscope of claim 14 , wherein a dimension of the opening is a value between 20 μm and 40 μm and a spacing between the pair of out-of-plane trim electrodes is a value between 0.1 μm and 1.0 μm.
16 . A method of operating a microelectromechanical systems (MEMS) yaw gyroscope having a planar proof mass with an opening suspended above a first pair of quadrature trim electrodes arranged along a first axis and a second pair of quadrature trim electrodes arranged along a second axis that is substantially perpendicular to the first axis, the method comprising:
generating an in-plane force at the opening of the planar proof mass in a first in-plane direction by applying a first direct current (DC) voltage to the first pair of quadrature trim electrodes;
generating an in-plane force at the opening of the planar proof mass in a second in-plane direction substantially perpendicular to the first in-plane direction by applying a second DC voltage to the second pair of quadrature trim electrodes;
driving in-plane motion of the planar proof mass along the first in-plane direction; and
sensing angular motion of the MEMS yaw gyroscope by sensing in-plane motion of the planar proof mass along the second in-plane direction.
17 . The method of claim 16 , wherein driving in-plane motion of the planar proof mass comprises applying an alternating current (AC) drive signal to a pair of in-plane drive electrodes.
18 . The method of claim 16 , wherein applying the DC voltage to the first pair of quadrature trim electrodes comprises applying the DC voltage to a pad connected to a subset of an array of quadrature trim electrodes.
19 . The method of claim 16 , wherein driving in-plane motion of the planar proof mass does not substantially alter a gap between the planar proof mass and the pair of quadrature trim electrodes.