MEMS FORCE BALANCE ACCELEROMETER
First Claim
1. A microelectromechanical (MEMS) accelerometer comprising:
- a housing;
a proof mass suspended within the housing by at least one flexure;
at least one planar coil located on the proof mass;
at least one magnet;
a first pole piece adjacent to at least one of the at least one magnets; and
a second pole piece,wherein at least one face of the first pole piece is positioned proximate a first side of the proof mass and at least one face of the second pole piece is positioned proximate a second side of the proof mass such that a magnetic flux field passes from the magnet, through the face of the first pole piece, through the at least one planar coil at a flux angle between approximately 30 degrees and approximately 60 degrees relative to the coil plane, and into the second pole piece.
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Accused Products
Abstract
Microelectromechanical (MEMS) accelerometer and acceleration sensing methods. A MEMS accelerometer includes a proof mass, a planar coil on the proof mass, a magnet, a first pole piece positioned proximate a first side of the proof mass, and a second pole piece positioned proximate a second side of the proof mass. A magnetic flux field passes from the magnet, through the first pole piece, through the planar coil at an angle between approximately 30 degrees and approximately 60 degrees relative to the coil plane, and into the second pole piece. The first pole piece may extend into a first recessed area of a first housing layer and the second pole piece may extend into a second recessed area of a second housing layer. A method includes sensing a capacitance of a pickoff in the MEMS accelerometer and rebalancing the MEMS accelerometer by sending a current through the planar coil.
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Citations
12 Claims
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1. A microelectromechanical (MEMS) accelerometer comprising:
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a housing; a proof mass suspended within the housing by at least one flexure; at least one planar coil located on the proof mass; at least one magnet; a first pole piece adjacent to at least one of the at least one magnets; and a second pole piece, wherein at least one face of the first pole piece is positioned proximate a first side of the proof mass and at least one face of the second pole piece is positioned proximate a second side of the proof mass such that a magnetic flux field passes from the magnet, through the face of the first pole piece, through the at least one planar coil at a flux angle between approximately 30 degrees and approximately 60 degrees relative to the coil plane, and into the second pole piece. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of operating a MEMS accelerometer, the method comprising:
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sensing a capacitance of a pickoff in the MEMS accelerometer; applying an annular magnetic field across a proof mass suspended by flexures within a housing, the magnetic field having an angle between 30 and 60 degrees with respect to the surface of the proof mass; and generating a force on the proof mass by applying a current through a planar coil located on a side of the proof mass, the current based on the sensed capacitance and the magnetic field value. - View Dependent Claims (11)
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12. A microelectromechanical (MEMS) accelerometer comprising:
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a silicon device layer comprising a MEMS proof mass suspended by at least one flexure; a first glass housing layer located on a first side of the device layer, the first glass housing layer defining a first recessed area; a second glass housing layer located on a second side of the device layer, the second glass housing layer defining a second recessed area; a planar coil located on the proof mass; a first annular magnet positioned on the first side of the proof mass; a first pole piece adjacent the first magnet, the first pole piece extending into the first recessed area, the first pole piece having a face proximate the proof mass; a second magnet positioned on a second side of the proof mass; a second pole piece adjacent the second magnet, the second pole piece extending into the second recessed area, the second pole piece having a face proximate the proof mass; and a magnetic return path structure coupled to the first magnet and the second magnet, wherein the face of the first pole piece and the face of the second pole piece are positioned such that a magnetic flux field passes through the planar coil at a flux angle of approximately 45 degrees relative to the coil plane.
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Specification