ANGULAR RATE SENSOR WITH DIFFERENT GAP SIZES
An angular rate sensor ( 20 ) includes conductive plates ( 24, 26, 28, 30 ) mounted on a substrate ( 22 ), and a structure ( 34 ) coupled to the substrate ( 22 ). The structure ( 34 ) includes a drive mass ( 36 ) and a sense mass ( 40 ) suspended above the plates ( 24, 26, 28, 30 ). The sense mass ( 40 ) includes regions ( 50, 52 ) separated by a sense axis of rotation ( 48 ). Each of the regions ( 50, 52 ) has an outer surface ( 56 ) and an inner surface ( 54 ). An inner gap ( 68 ) exists between the inner surface ( 54 ) and plates ( 24, 26, 28 ). An outer gap ( 70 ) exists between the outer surface ( 56 ) and the plate ( 30 ). The outer gap ( 70 ) is larger than the inner gap ( 68 ). Plates ( 24, 26, 28 ) may be electrodes for force feedback, frequency tuning, and/or quadrature compensation. Plates ( 30 ) may be electrodes for sensing angular velocity.
1 . An angular rate sensor comprising:
a substrate having a surface;
conductive plates fixedly mounted on said surface, said conductive plates including a first electrode and a second electrode;
a drive mass flexibly coupled to said substrate surface, said drive mass being configured to move with an oscillatory motion;
a sense mass having first and second regions separated by an axis of rotation, wherein a first gap exists between a first portion of said sense mass and said first electrode, and a second gap exists between a second portion of said sense mass and said second electrode, said second gap being larger than said first gap; and
flexible support elements connecting said sense mass to said drive mass.
2 . An angular rate sensor as claimed in claim 1 wherein each of said first and second regions includes a first surface and a second surface laterally displaced from said axis of rotation such that said first surface is interposed between said axis of rotation and said second surface, said first surface having a corrugation formed thereon, said first gap existing between said corrugation and said first electrode, and said second gap existing between said second surface and said second electrode.
3 . An angular rate sensor as claimed in claim 1 wherein said axis of rotation is a first axis of rotation oriented parallel to said surface, and said drive mass together with said sense mass are configured to move with said oscillatory motion about a second axis of rotation that is perpendicular to said surface, and said flexible support elements enable said sense mass to oscillate about said first axis of rotation in response to an angular velocity about a third axis of rotation that is perpendicular to each of said first and second axes of rotation.
4 . An angular rate sensor as claimed in claim 1 further comprising a third electrode fixedly mounted on said surface of said substrate, and said first gap exists between said first portion of said sense mass and said third electrode.
5 . An angular rate sensor as claimed in claim 1 wherein said first electrode is a frequency tuning electrode.
6 . An angular rate sensor as claimed in claim 5 wherein said second electrode is a sense electrode.
7 . An angular rate sensor as claimed in claim 1 wherein said first electrode is a force feedback electrode.
8 . An angular rate sensor as claimed in claim 1 wherein said first electrode is a quadrature compensation electrode.
9 . An angular rate sensor as claimed in claim 1 wherein said second electrode is a sense electrode.
10 . An angular rate sensor as claimed in claim 9 wherein said second gap exists between said second portion of said sense mass and a first portion of said sense electrode, and said first gap exists between said first portion of said sense mass and a second portion of said sense electrode.
11 . An angular rate sensor as claimed in claim 1 wherein said first electrode is a frequency tuning electrode, said second electrode is a sense electrode, and said angular rate sensor further comprises a force feedback electrode fixedly mounted on said surface of said substrate, and said first gap exists between said first portion of said sense mass and said force feedback electrode.
12 . An angular rate sensor as claimed in claim 1 wherein said sense mass is a first sense mass, said axis of rotation is a first axis of rotation, said flexible support elements are first flexible support elements, and said angular rate sensor further comprises:
third and fourth electrodes fixedly mounted on said surface of said substrate;
a second sense mass having third and forth regions separated by a second axis of rotation, wherein a third gap exists between a third portion of said second sense mass and said third electrode, and a fourth gap exists between a fourth portion of said second sense mass and said fourth electrode, said fourth gap being larger than said third gap; and
second flexible support elements connecting said second sense mass to said drive mass.
13 . An angular rate sensor comprising:
a substrate having a surface;
conductive plates fixedly mounted on said surface, said conductive plates including frequency tuning electrodes and sense electrodes;
a drive mass coupled to said substrate surface, said drive mass being configured to move with an oscillatory motion;
a sense mass having first and second regions separated by an axis of rotation, each of said first and second regions having a first gap existing between a first portion of said sense mass and one of said frequency tuning electrodes, and having a second gap existing between a second portion of said sense mass and one of said sense electrodes, said second gap being larger than said first gap; and
flexible support elements connecting said sense mass to said drive mass.
14 . An angular rate sensor as claimed in claim 13 wherein said each of said first and second regions includes a first surface and a second surface laterally displaced from said axis of rotation such that said first surface is interposed between said axis of rotation and said second surface, said first surface having a corrugation formed thereon, said first gap existing between said corrugation and said one of said frequency tuning electrodes, and said second gap existing between said second surface and said one of said sense electrodes.
15 . An angular rate sensor as claimed in claim 13 wherein said axis of rotation is a first axis of rotation oriented parallel to said surface, said drive mass together with said sense mass are configured to move with said oscillatory motion about a second axis of rotation that is perpendicular to said surface, and said flexible support elements enable said sense mass to oscillate about said first axis of rotation in response to an angular velocity about a third axis of rotation that is perpendicular to each of said first and second axes of rotation.
16 . An angular rate sensor as claimed in claim 13 further comprising force feedback electrodes fixedly mounted on said surface of said substrate, wherein for said each of said first and second regions, said first gap exists between said first portion of said sense mass and one of said force feedback electrodes.
17 . An angular rate sensor as claimed in claim 13 further comprising quadrature compensation electrodes fixedly mounted on said surface of said substrate, wherein for said each of said first and second regions, said first gap exists between said first portion of said sense mass and one of said quadrature compensation electrodes.
18 . An angular rate sensor as claimed in claim 13 wherein for said each of said first and second regions, said second gap exists between said second portion of said sense mass and a first portion of said sense electrode, and said first gap exists between said first portion of said sense mass and a second portion of said sense electrode.
19 . An angular rate sensor comprising:
a substrate having a surface;
conductive plates fixedly mounted on said surface, said conductive plates including frequency tuning electrodes and sense electrodes;
a drive mass coupled to said substrate surface, said drive mass being configured to move with an oscillatory motion;
a sense mass having first and second regions separated by an axis of rotation, wherein each of said first and second regions includes a first surface and a second surface laterally displaced from said axis of rotation such that said first surface is interposed between said axis of rotation and said second surface, a first gap exists between said first surface and one of said frequency tuning electrodes, and a second gap exists between said second surface and one of said sense electrodes, said second gap being larger than said first gap; and
flexible support elements connecting said sense mass to said drive mass.
20 . An angular rate sensor as claimed in claim 19 further comprising force feedback electrodes and quadrature compensation electrodes fixedly mounted to said surface of said substrate, said first gap existing between said first surface and one each of said force feedback electrodes and said quadrature compensation electrodes.