Angular rate sensor with quadrature error compensation
View Patent ↗An angular rate sensor includes a substrate, a drive mass flexibly coupled to the substrate, and a sense mass suspended above the substrate and flexibly coupled to the drive mass via flexible support elements. An electrode structure is mechanically coupled to, but electrically isolated from, the drive mass and is spaced apart from the substrate so that it is not in contact with the substrate. The electrode structure is configured to produce a signal that indicates movement of the sense mass relative to the electrode when the sensor is subjected to angular velocity. When the angular rate sensor experiences quadrature error, the drive mass, the sense mass, and the electrode structure move together relative to the sense axis. Since the sense mass and the electrode structure move together in response to quadrature error, there is little relative motion between the sense mass and the electrode structure so that quadrature error is largely eliminated.
1. An angular rate sensor comprising:
a substrate;
a drive mass flexibly coupled to said substrate, said drive mass comprising a frame structure having a central opening;
a sense mass suspended above said substrate and flexibly coupled to said drive mass via flexible support elements, said sense mass residing in said central opening; and
an electrode structure spaced apart from said substrate, said electrode structure comprising a sense plate fixedly attached to said drive mass at two locations on said frame structure so that said sense plate fully extends across at least a portion of said central opening and is vertically spaced apart from said sense mass, said electrode structure being configured to produce a sense signal that indicates movement of said sense mass relative to said electrode structure, wherein
said drive mass, said sense mass, and said electrode structure move together with an oscillatory drive motion relative to a drive axis;
while said drive mass, said sense mass, and said electrode structure move together with said oscillatory drive motion, said flexible support elements enable said sense mass to oscillate relative to a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to each of said drive and said sense axes, wherein oscillation of said sense mass in response to said angular velocity produces said sense signal between said sense mass and said electrode structure; and
said drive mass, said sense mass, and said electrode structure move together along said sense axis in response to quadrature error thereby resulting in substantially no relative motion between said sense mass and said electrode structure to reduce imposition of a signal error component from said quadrature error on said sense signal.
2. An angular rate sensor as claimed in claim 1 wherein said electrode structure is not in contact with said substrate.
3. An angular rate sensor as claimed in claim 1 wherein said electrode structure is electrically isolated from said drive mass.
4. An angular rate sensor as claimed in claim 1 wherein said electrode structure is interposed between said sense mass and a surface of said substrate.
5. An angular rate sensor as claimed in claim 1 wherein said substrate includes a cavity extending inwardly from a surface of said substrate, said drive mass and said sense mass are suspended above said cavity, and said electrode structure is interposed between said cavity and said drive and sense masses.
6. An angular rate sensor as claimed in claim 1 wherein:
said sense plate is a first sense plate;
said drive mass includes first and second regions separated by an axis of rotation oriented parallel to a surface of said substrate;
said sense mass includes third and fourth regions separated by said axis of rotation, said first and third regions being disposed on a first side of said axis of rotation, and said second and fourth regions being disposed on a second side of said axis of rotation;
said first sense plate is coupled to said first region of said drive mass and extends across said third region of said sense mass; and
said electrode structure further comprises a second sense plate coupled to said second region of said drive mass, said second sense plate extending across said fourth region of said sense mass.
7. An angular rate sensor as claimed in claim 6 wherein said second sense plate is fixedly attached to said second region of said drive mass at two locations on said frame structure so that said second sense plate fully extends across and is vertically spaced apart from said fourth region of said sense mass.
8. An angular rate sensor comprising:
a substrate;
a drive mass flexibly coupled to said substrate, said drive mass comprising a frame structure having a central opening;
a sense mass suspended above said substrate and flexibly coupled to said drive mass via flexible support elements, said sense mass residing in said central opening;
an electrode structure spaced apart from said substrate by an open gap, said electrode structure comprising a sense plate fixedly attached to said drive mass at two locations on said frame structure so that said sense plate fully extends across at least a portion of said central opening and is vertically spaced apart from said sense mass, said electrode structure being configured to produce a sense signal that indicates movement of said sense mass relative to said electrode structure; and wherein said drive mass, said sense mass, and said electrode structure move together relative to the substrate.