Inertial measurement unit
First Claim
1. An inertial measurement unit, comprising a cantilevered proof mass, an electrostatic drive for putting the proof mass into a controlled trajectory, and a capacitive sensor for measuring the position and motion of the proof mass, wherein the inertial measurement unit is configured:
- (a) to measure lateral acceleration and rotation of the inertial measurement unit by measuring perturbations in the trajectory from a trajectory that the proof mass would travel in a fixed, non-rotating inertial frame;
(b) to apply a first voltage V1(t)=Vb1+m t to a first set of electrodes and a second voltage V2(t)=Vb2−
m t to a second set of electrodes, where m is a constant and the first and second voltages are changing at a constant rate; and
(c) to measure a displacement current induced in the proof mass, which displacement current provides a signed measurement of spatial displacement of the proof mass.
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Abstract
In exemplary embodiments of this invention, an inertial measurement unit (IMU) includes a cantilevered proof mass and electrostatic drive. The electrostatic drive puts the proof mass into a controlled trajectory in which it oscillates rapidly, for example, by vibrating back and forth in a plane or traveling in a circular or elliptical orbit. The IMU detects lateral or angular acceleration of the IMU, by measuring the perturbations of the proof mass trajectory from the expected motion in a fixed, non-rotating inertial frame. In exemplary embodiments of this invention, the proof mass position and motion are measured by methods of differential potential measurement (with constant slope voltage), differential displacement current measurement, or phase-sensitive or synchronous detection of motion.
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Citations
15 Claims
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1. An inertial measurement unit, comprising a cantilevered proof mass, an electrostatic drive for putting the proof mass into a controlled trajectory, and a capacitive sensor for measuring the position and motion of the proof mass, wherein the inertial measurement unit is configured:
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(a) to measure lateral acceleration and rotation of the inertial measurement unit by measuring perturbations in the trajectory from a trajectory that the proof mass would travel in a fixed, non-rotating inertial frame; (b) to apply a first voltage V1(t)=Vb1+m t to a first set of electrodes and a second voltage V2(t)=Vb2−
m t to a second set of electrodes, where m is a constant and the first and second voltages are changing at a constant rate; and(c) to measure a displacement current induced in the proof mass, which displacement current provides a signed measurement of spatial displacement of the proof mass. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An inertial measurement unit, comprising a cantilevered proof mass, an electrostatic drive for putting the proof mass into a controlled trajectory, and a capacitive sensor for measuring the position and motion of the proof mass, wherein the inertial measurement unit is configured:
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(a) to measure lateral displacement and rotation of the inertial measurement unit by measuring perturbations in the trajectory from a trajectory that the proof mass would travel in a fixed, non-rotating inertial frame; (b) to create a spatially varying electric potential by applying a negative voltage to a first set of electrodes and a positive voltage to a second set of electrodes; and (c) to measure voltage on the proof mass to determine position of the proof mass. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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Specification
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- Resources
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Current AssigneeMassachusetts Institute of Technology
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Original AssigneeMassachusetts Institute of Technology
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InventorsPost, Ernest, Gershenfeld, Neil
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Primary Examiner(s)CHAPMAN JR, JOHN E
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Application NumberUS13/023,537Publication NumberTime in Patent Office1,022 DaysField of Search735/040.4, 735/041.2, 735/041.5, 735/143.2US Class Current73/504.04CPC Class CodesG01C 19/56 Turn-sensitive devices usin...G01P 15/097 by vibratory elementsG01P 2015/0805 being provided with a parti...
