Comb drive micromechanical tuning fork gyro
First Claim
1. An inertial rate sensor comprising:
- a first weighted element suspended to rotate about a first axis and adapted to vibrate in a direction substantially orthogonal to said first axis;
a set of driven electrodes projecting from said suspended element in the direction of vibration;
a set of drive electrodes freely meshing with said set of driven electrodes;
a source of vibration drive contacting, through said suspended element, said set of driven electrodes and said set of drive electrodes with opposite polarity signals to induce vibration of said suspended element;
a plurality of position sensors placed at locations facing said suspended element wherein spacing between said plurality of position sensors and said suspended element varies with rotation thereof about said axis;
an electrical signal source for energizing at least some of said plurality of position sensors relative to said suspended element; and
a signal sensor responsive to at least a subset of said plurality of position sensors for receiving a signal varying with rotation of said element about said axis.
1 Assignment
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Accused Products
Abstract
A microfabricated tuning fork rate sensitive structure and drive electronics in which vibrational forces are communicated through a set of meshing drive and driven finger electrodes associated with each of two vibrating elements. The vibrating elements are supported in a rotatable assembly between first and second support electrodes which are in turn suspended by flexures for rotation about an axis passing through the flexures and through a point midway between the vibrating elements. Additional masses are formed onto the vibrating elements to improve overall sensor sensitivity. Sense electrodes for detecting capacitive changes between the support electrodes and the sense electrodes are positioned at each end of the support electrodes. Drive electronics are connected between the driven fingers of the vibrating elements and the drive electrode fingers which mesh with them to cause vibration. Excitation is provided between the support electrodes and the sense electrodes. Any change in signal resulting from rotation of the assembly and the resulting variation in capacitance between the support electrodes and the sense electrodes is sensed as a measure of inertial rate. A torque loop may be additionally formed using the sense electrodes in order to re-torque the assembly to a neutral position in a torque-to-balance loop.
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Citations
12 Claims
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1. An inertial rate sensor comprising:
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a first weighted element suspended to rotate about a first axis and adapted to vibrate in a direction substantially orthogonal to said first axis; a set of driven electrodes projecting from said suspended element in the direction of vibration; a set of drive electrodes freely meshing with said set of driven electrodes; a source of vibration drive contacting, through said suspended element, said set of driven electrodes and said set of drive electrodes with opposite polarity signals to induce vibration of said suspended element; a plurality of position sensors placed at locations facing said suspended element wherein spacing between said plurality of position sensors and said suspended element varies with rotation thereof about said axis; an electrical signal source for energizing at least some of said plurality of position sensors relative to said suspended element; and a signal sensor responsive to at least a subset of said plurality of position sensors for receiving a signal varying with rotation of said element about said axis. - View Dependent Claims (2, 3, 4)
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5. A comb drive tuning fork microfabricated structure comprising:
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a substrate; an assembly on said substrate having; first and second elongate vibratable elements joined at the ends thereof by first and second support electrodes so that said first and second vibrating elements extend substantially parallel to each other and to a rotation axis running therebetween; first and second flexures extending from said support electrodes away from said first and second vibratable elements to points of attachment to said substrate along said axis allowing said first and second support electrodes and said first and second vibratable elements to rotate about said axis; first and second weights respectively attached to said first and second vibratable elements; each said first and second vibratable element having a plurality of driven electrodes projecting away therefrom in a direction orthogonal to said axis; first and second drive electrodes extending between the driven electrodes of said first and second vibratable elements, said first and second drive electrodes being physically attached to said substrate but electrically isolated therefrom; plural sense electrodes in said substrate under said support electrodes at locations thereof distant from said axis of rotation. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12)
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Specification