Comb-drive micromechanical tuning fork gyroscope with piezoelectric readout
First Claim
1. An inertial rate sensor comprising:
- a semiconductor mass;
a plurality of suspension elements parallel to a first axis and each having at least one end thereof anchored to said mass;
a first weighted element suspended from said suspension elements to rotate about said 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 said set of drive electrodes to induce vibration of said suspended element;
a plurality of position sensors placed at locations along said suspension elements which are thinner than regions of said suspension elements which are thinner than regions of said suspension elements where no position sensors are disposed, wherein rotation of said suspended element about said first axis creates strain-induced voltage within said position sensors; 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.
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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 beams and the substrate are positioned on the substrate beneath each end of the support beams. In an alternative embodiment, piezoelectric sense capacitors are disposed on the flexures for detecting rotation 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 or within the piezoelectric capacitors 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.
213 Citations
24 Claims
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1. An inertial rate sensor comprising:
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a semiconductor mass; a plurality of suspension elements parallel to a first axis and each having at least one end thereof anchored to said mass; a first weighted element suspended from said suspension elements to rotate about said 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 said set of drive electrodes to induce vibration of said suspended element; a plurality of position sensors placed at locations along said suspension elements which are thinner than regions of said suspension elements which are thinner than regions of said suspension elements where no position sensors are disposed, wherein rotation of said suspended element about said first axis creates strain-induced voltage within said position sensors; 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)
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4. 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 elements so that said first and second vibratable elements extend substantially parallel to each other and to a rotation axis running therebetween; first and second flexures extending from said support elements away from said first and second vibratable elements to points of attachment to said substrate along said axis allowing said first and second support elements 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; and at least one sense element disposed on each of said first and second flexures, said at least one sense element being disposed on a region of said flexures thinner than regions of said flexures not having said at least one sense element disposed thereon, wherein rotation of said vibratable elements about said rotation axis creates a strain-induced voltage in said at least one sense element. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A micromechanical transducer comprising:
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a silicon substrate; an assembly on said substrate having; first and second proof mass structures each suspended above said substrate by at least one support structure attached therebetween so that said proof mass structures extend substantially parallel to each other and to a rotational axis extending therebetween; each said first and second proof mass structures having a plurality of driven electrodes projecting away therefrom in a direction orthogonal to said axis, said plurality of driven electrodes including an outer set of driven electrodes extending away from said axis and an inner set extending toward said axis; first and second drive electrodes extending between said outer set of driven electrodes of said first and second proof mass structures, and third drive electrodes extending between said inner set of driven electrodes of said first and second proof mass structures, said first, second and third drive electrodes being physically attached to said substrate but electrically isolated therefrom; and a plurality of sense elements disposed on said at least one support structure for generating a signal representative of a degree of rotation of said first and second proof mass structures about said rotational axis due to strain induced by said rotation, said plurality of sense elements being disposed along regions of said support structure which are thinner than surrounding regions of said support structure. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification