Sourceless orientation sensor
First Claim
1. A sourceless orientation sensor, comprising:
- a) two-axis magnetic sensing means for measuring the Earth'"'"'s magnetic field,b) measuring means for measuring elevation or roll angle of said object with respect to a fixed reference three-dimensional coordinate frame, andc) computing means for controlling the taking of measurements by said magnetic sensing means and measuring means and converting said measurements into azimuth, elevation and roll angles relative to a fixed coordinate frame, wherein said computing means receives signals from an initial calibration procedure of said magnetic sensing means and determines constant Earth magnetic field intensity and therefrom calculates a third axis component of the Earth'"'"'s magnetic field.
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Accused Products
Abstract
In a sourceless orientation sensor, the sensor measures the three orientation angles azimuth, elevation and roll in a fixed reference three-dimensional coordinate frame. The sensor utilizes a three-axis magnetic sensor to measure changes in the Earth'"'"'s magnetic field in order to determine the azimuth and roll (or elevation) angles after the elevation (or roll) angle has been determined by other means. A first embodiment utilizes a separate sensor to measure the elevation (or roll) angle in a fixed reference three-dimensional coordinate frame while a three axis magnetic sensor is used to measure the Earth'"'"'s magnetic field. The azimuth and the roll (or elevation) angles are then determined from these measurements. A second embodiment utilizes a combination of a three-axis accelerometer to sense the Earth'"'"'s gravity to measure the absolute elevation and roll angles for slow motions and a two-axis rate sensor to measure the azimuth and elevation velocities in the sensor frame. A direct method employing translation and integration is used to find the azimuth and elevation angles in the fixed reference three-dimensional coordinate frame. The roll angle is then found from the magnetic sensor measurements. Other embodiments are disclosed.
349 Citations
36 Claims
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1. A sourceless orientation sensor, comprising:
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a) two-axis magnetic sensing means for measuring the Earth'"'"'s magnetic field, b) measuring means for measuring elevation or roll angle of said object with respect to a fixed reference three-dimensional coordinate frame, and c) computing means for controlling the taking of measurements by said magnetic sensing means and measuring means and converting said measurements into azimuth, elevation and roll angles relative to a fixed coordinate frame, wherein said computing means receives signals from an initial calibration procedure of said magnetic sensing means and determines constant Earth magnetic field intensity and therefrom calculates a third axis component of the Earth'"'"'s magnetic field. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of measuring the orientation of an object, including the steps of:
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a) providing a sourceless orientation sensor comprising; i) two-axis magnetic sensing means for measuring the Earth'"'"'s magnetic field, ii) measuring means for measuring elevation or roll angle of said object with respect to a fixed reference three-dimensional coordinate frame; and iii) a computer interconnected with said sensing means and measuring means; b) programming said computer with first data from an initial calibration procedure of measurements of the constant intensity of the Earth'"'"'s magnetic field; c) feeding said computer second data from said sensing means concerning two axes of the Earth'"'"'s magnetic field; d) calculating, in said computer, a third axis of the Earth'"'"'s magnetic field; e) feeding said computer third data from said measuring means concerning elevation or roll angle of said object in a fixed reference three-dimensional coordinate frame; f) calculating orientation of said object in terms of azimuth, elevation and roll relative to a fixed reference three-dimensional coordinate frame. - View Dependent Claims (8, 9)
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10. A sourceless orientation sensor for determining orientation of an object, comprising:
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a) two-axis magnetic sensing means for measuring direction and strength of the Earth'"'"'s magnetic field; b) accelerometer means for measuring acceleration of the Earth'"'"'s gravity force; c) measuring means for measuring elevation and azimuth angle velocities of said object with respect to a sensor frame; and d) computer means for controlling taking of said measurements and for converting said measurements into azimuth, elevation and roll angles of said object with respect to a fixed reference three-dimensional coordinate frame. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A method of measuring the orientation of an object, including the steps of:
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a) providing a sourceless orientation sensor comprising; i) two-axis magnetic sensing means for measuring the Earth'"'"'s magnetic field; ii) accelerometer means for measuring acceleration of the Earth'"'"'s gravity force; iii) measuring means for measuring elevation and azimuth angle velocities of said object in a sensor frame; and iv) a computer interconnected with said sensing means and measuring means; b) programming said computer with first data from an initial calibration procedure of measurements of the constant intensity of the Earth'"'"'s magnetic field; c) feeding said computer second data from said sensing means concerning two axes of the Earth'"'"'s magnetic field; d) calculating, in said computer, a third axis of the Earth'"'"'s magnetic field; e) feeding said computer third data from said accelerometer means concerning acceleration of the Earth'"'"'s gravity force; f) said computer converting said angular velocity measurements into elevation and azimuth angles of said object in a fixed reference three-dimensional coordinate frame; g) said computer further converting said second data from said sensing means into roll angle of said object with respect to a fixed reference three-dimensional coordinate frame; h) said computer outputting azimuth, elevation and roll angles with respect to a fixed reference three-dimensional coordinate frame. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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35. A method of measuring the orientation of an object, comprising:
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a) providing a sourceless orientation sensor comprising; i) two-axis magnetic sensing means for measuring Earth'"'"'s magnetic field; ii) accelerometer means for measuring acceleration of Earth'"'"'s gravity force; iii) measuring means for measuring elevation velocity of said object in a sensor frame; iv) a computer interconnected with said sensing means and said measuring means; b) programming said computer with first data from an initial calibration procedure of measurements of constant intensity of the Earth'"'"'s magnetic field; c) feeding said computer with second data from said magnetic sensing means concerning two axes of Earth'"'"'s magnetic field; d) calculating, in said computer, a third axis of the Earth'"'"'s magnetic field; e) feeding said computer third data from said accelerometer means concerning acceleration of Earth'"'"'s gravity force; f) said computer converting said elevation velocity and a last determined azimuth velocity into elevation and azimuth angle estimates of said object relative to a fixed reference three-dimensional coordinate frame; g) said computer further converting said signals from said magnetic sensing means into roll angle estimates of said object relative to said fixed reference three-dimensional coordinate frame; h) said computer further using said signals from said magnetic sensing means to find a different azimuth angle, comparing this azimuth angle to an azimuth angle estimate and finding a more accurate azimuth angle velocity estimate; i) said computer repeating steps f-h until a difference between two consecutively determined azimuth angles is less than a preprogrammed level; j) said computer outputting to a host computer said azimuth, elevation and roll angles of said object relative to said fixed reference three-dimensional coordinate frame. - View Dependent Claims (36)
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Specification