Apparatus and method for leveling a gravity measurement device
First Claim
1. In a device for measuring the acceleration of gravity using an accelerometer, an apparatus for vertically orienting an acceleration sensitive axis of the accelerometer, comprising:
- (a) first means for rotating the accelerometer about a first axis that is orthogonal to the acceleration sensitive axis;
(b) second means for rotating the accelerometer about a second axis that is angularly displaced from the first axis;
(c) drive means, connected to the first and the second means, for selectively driving the first and the second means to orient the acceleration sensitive axis of the accelerometer in a plurality of substantially horizontal directions, defining a level plane; and
(d) processor means, responsive to a signal produced by the accelerometer indicative of the acceleration of gravity, for controlling the drive means as a function of said signle in order to establish the level plane, and further operative to vertically align the acceleration sensitive axis of the accelerometer relative to the level plane.
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Accused Products
Abstract
Apparatus and method for establishing a level plane and with respect to the level plane, vertically aligning an acceleration sensitive axis of a gravity measurement device (10). The gravity measurement device includes an accelerometer (68), which is rotatably mounted on a gimbal shaft (62) within a gimbal frame (54). The gimbal frame is also rotatable about a longitudinal axis that is preferably oriented at a right angle to the longitudinal axis of the gimbal shaft. A stepping motor (20) is connected through an antibacklash gear (30), an idler gear (32) and an antibacklash gear (48) to a drive shaft (50). Rotation of this drive shaft causes the accelerometer to rotate about the gimbal shaft. In a similar fashion, a stepping motor (22) is drivingly connected to a drive shaft (56), used to rotate the gimbal frame. A control (140) selectively energizes the stepping motors, so that the acceleration sensitive axis of the accelerometer is rotated until an output signal from the acceleometer indicates that the acceleration of gravity is zero and thus that the sensitive axis is level at two cross axis positions, thereby determining a level reference plane. The control then causes the accelerometer to be rotated 90° relative to the reference plane, so that the acceleration sensitive axis is vertically aligned, thereby enabling the accelerometer to measure the local acceleration of gravity with minimal error due to vertical alignment.
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Citations
22 Claims
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1. In a device for measuring the acceleration of gravity using an accelerometer, an apparatus for vertically orienting an acceleration sensitive axis of the accelerometer, comprising:
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(a) first means for rotating the accelerometer about a first axis that is orthogonal to the acceleration sensitive axis; (b) second means for rotating the accelerometer about a second axis that is angularly displaced from the first axis; (c) drive means, connected to the first and the second means, for selectively driving the first and the second means to orient the acceleration sensitive axis of the accelerometer in a plurality of substantially horizontal directions, defining a level plane; and (d) processor means, responsive to a signal produced by the accelerometer indicative of the acceleration of gravity, for controlling the drive means as a function of said signle in order to establish the level plane, and further operative to vertically align the acceleration sensitive axis of the accelerometer relative to the level plane. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a gravity measurement device, an apparatus for determining a level disposition that is orthogonal to a gravitational acceleration, comprising:
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(a) a first gimbal, mounted on the gravity measurement device and rotatable about a first axis; (b) a second gimbal, mounted on the first gimbal and rotatable about a second axis, which is disposed at a substantial angular displacement relative to the first axis and intersects it; (c) means for sensing acceleration along an acceleration sensitive axis and producing a signal indicative of the acceleration, said means being mounted on the second gimbal so that the acceleration sensitive axis is disposed at a right angle relative to the second axis, being rotatable about both the first and second axes; and (d) means for incrementally rotating the first and the second gimbals to orient the acceleration sensitive axis to a first position and then to a second position at which the signal produced by the acceleration sensing means indicates substantially a minimum acceleration due to gravity, said first and second positions defining a level plane for the first and the second gimbals, so that the acceleration sensitive axis may be oriented vertically relative to the level plane. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. In a device for measuring the acceleration of gravity using an accelerometer having an acceleration sensitive axis, a method for vertically orienting the acceleration sensitive axis of the accelerometer, comprising the steps of:
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(a) rotating the accelerometer about a first axis to a first position in which the acceleration sensitive axis is horizontally disposed; (b) rotating the accelerometer about a second axis, orthogonal to the first, to a second position in which the acceleration sensitive axis is horizontally disposed; and (c) rotating the accelerometer about the first and the second axes to a third position in which the acceleration sensitive axis is displaced by substantially ninety degrees relative to its disposition at the first and the second positions, said third position of the accelerometer orienting the acceleration sensitive axis vertically. - View Dependent Claims (18)
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19. In a precision gravity measurement device having an accelerometer for sensing the acceleration of gravity along a sensitive axis and producing a signal indicative thereof, a method for determining a level disposition that is orthogonal to the acceleration of gravity, comprising the steps of:
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(a) incrementally rotating the accelerometer about a first axis that is at right angles to the acceleration sensitive axis, to a position at which the signal the accelerometer produces indicates substantially a zero component of the acceleration of gravity along the sensitive axis, thereby defining a first level point associated with the first axis; (b) rotating the accelerometer through an angle of ninety degrees about the first axis to a position where its sensitive axis is generally oriented vertically; (c) incrementally rotating the accelerometer about a second axis that is angularly displaced relative to the first axis, to a position at which the signal the accelerometer produces indicates substantially a zero component of the acceleration of gravity along the sensitive axis, thereby defining a second level point associated with the second axis; and (d) incrementally rotating the accelerometer about at least one of the first and the second axes, through an angle determined relative to the first and the second level points, respectively, so that the acceleration sensitive axis is substantially vertical, and so that the accelerometer accurately measures the acceleration of gravity with minimal vertical alignment errors. - View Dependent Claims (20, 21, 22)
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Specification