Micromachined microaccelerometer for measuring acceleration along three axes
First Claim
1. A microaccelerometer comprising:
- a thin planar sheet having first and second substantially planar surfaces, said sheet having a cavity extending between said first and second substantially planar surfaces, wherein said cavity has a cross-section which has a narrowest point at an interior location in said sheet;
a free-mass having a pair of ends and a central portion between said ends, wherein said free-mass has a cross-section with said central portion being narrower than said narrowest point of said sheet and said ends being wider than said narrowest point of said sheet to locate said free-mass in a position relative to said sheet, whereby said free-mass is restrained by and moveable with respect to said sheet;
sensing means for detecting said free-mass'"'"'s position relative to said sheet and generating one or more signals indicative of said position of said free-mass;
position correction means for receiving position indication signals from said sensing means, exerting a restorative force on said free-mass to an equilibrium position, and generating one or more signals indicative of said restorative force; and
computing means for generating an acceleration value from said one or more signals indicative of said position of said free-mass and said one or more signals indicative of said restorative force.
1 Assignment
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Accused Products
Abstract
The present invention relates to a microaccelerometer employing a single free-mass and capable of measuring acceleration along three coordinate axes, and a process for fabricating through micromachining and microelectronic techniques a microaccelerometer employing a free-mass. A microaccelerometer preform is constructed by chemically coating and etching a silicon wafer to form a support member and a free-mass surrounded by the member. The free-mass is movable with respect to, but constrained by the silicon support member. Acceleration measurements are obtained by circuits which sense changes in the position of the free-mass with respect to an equilibrium position, induced by a change in the rate of acceleration of the accelerometer, and the electromagnetic force required to restore the free-mass to its equilibrium position.
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Citations
18 Claims
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1. A microaccelerometer comprising:
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a thin planar sheet having first and second substantially planar surfaces, said sheet having a cavity extending between said first and second substantially planar surfaces, wherein said cavity has a cross-section which has a narrowest point at an interior location in said sheet; a free-mass having a pair of ends and a central portion between said ends, wherein said free-mass has a cross-section with said central portion being narrower than said narrowest point of said sheet and said ends being wider than said narrowest point of said sheet to locate said free-mass in a position relative to said sheet, whereby said free-mass is restrained by and moveable with respect to said sheet; sensing means for detecting said free-mass'"'"'s position relative to said sheet and generating one or more signals indicative of said position of said free-mass; position correction means for receiving position indication signals from said sensing means, exerting a restorative force on said free-mass to an equilibrium position, and generating one or more signals indicative of said restorative force; and computing means for generating an acceleration value from said one or more signals indicative of said position of said free-mass and said one or more signals indicative of said restorative force. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A preform for use in an accelerometer comprising:
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a thin planar sheet having first and second substantially planar surfaces, said sheet having a cavity extending between said first and second substantially planar surfaces, wherein said cavity has a cross-section which has a narrowest point at an interior location in said sheet and is configured as opposing frustopyramids having opposed bases proximate said first and second substantially planar surfaces of said sheet; a free-mass having a pair of ends and a central portion between said ends, wherein said free-mass has a cross-section with said central portion being narrower than said narrowest point of said sheet and said ends being wider than said narrowest point of said sheet to locate said free-mass in a position relative to said sheet, said free-mass being configured as opposing frustopyramids having opposed bases and each frustopyramid of said free-mass being aligned with a frustopyramid of said cavity, whereby said free-mass is restrained by and moveable with respect to said sheet in response to acceleration. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification