Method and apparatus for calibrating an electronic compass to account for alignment errors in the compass windings
First Claim
1. A method for calibrating an electronic compass comprising the steps of:
- providing an electronic compass having at least two sense windings disposed at a known nominal angle plus a difference angle with respect to one another;
measuring and storing, as data outputs of the sense windings;
outputs of the sense windings provided for a number of compass headings;
calculating the difference angle between the sense windings;
by using the stored winding output and heading data; and
using said calculated difference angle to relate actual compass heading to outputs of said sense windings.
2 Assignments
0 Petitions
Accused Products
Abstract
An electronic compass (10) having at least two sense windings (11, 12) is mounted in a vehicle. The outputs (x(h), y(h)) of the windings are measured for a number of compass directions (headings). From this data an error difference angle (φ), from a nominal angle, which actually exists between the output windings is calculated. Preferably a look-up table (21, 39) is created relating actual compass heading (h) to measured sense winding outputs by utilizing the calculated error difference angle (φ). This table is then utilized for calculating actual compass heading based on actual measured sense winding outputs. The calculated error angle (φ) can also be used to calibrate the compass without creating a look-up table. The calibrated compass compensates for misalignment of the sense windings and provides a more accurate electronic compass without requiring creating a calibration table by orienting the compass in a very large number of exactly known directions.
60 Citations
36 Claims
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1. A method for calibrating an electronic compass comprising the steps of:
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providing an electronic compass having at least two sense windings disposed at a known nominal angle plus a difference angle with respect to one another; measuring and storing, as data outputs of the sense windings;
outputs of the sense windings provided for a number of compass headings;calculating the difference angle between the sense windings;
by using the stored winding output and heading data; andusing said calculated difference angle to relate actual compass heading to outputs of said sense windings. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for calibrating an electronic compass comprising the steps of:
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(a) providing an electronic compass having x and y sense windings disposed nominally orthogonal with respect to one another; (b) orienting the electronic compass in an initial known heading direction (hi); (c) measuring and storing as data at least one output of the sense windings provided for the known initial heading direction; (d) measuring and storing, as data outputs of the sense windings, outputs of the sense windings provided for a number of other compass headings; (e) calculating at least one coordinate of the center and at least one radii of an ellipse formed by a locus of said stored outputs of each of said sense windings plotted against one another; (f) calculating a non-orthogonal error difference angle (φ
) between the sense windings by using the calculated center and radii data and the initial heading and initial output winding data; and(g) creating and storing a look-up table relating actual compass heading to the outputs of sense windings by using said calculated error difference angle; whereby said look-up table can be used for calibrating the compass to compensate for non-orthogonal alignments of the sense windings. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A calibrated electronic compass comprising:
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an electronic compass having at least two sense windings disposed at a known nominal angle plus a difference angle with respect to one another; means for measuring and storing, as data outputs of the sense windings, outputs of the sense windings provided for a number of compass headings; means for calculating the difference angle between the sense windings by using the stored winding output and heading data; and means for using said calculated difference angle to relate actual compass heading to outputs of said sense windings. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A calibrated electronic compass comprising:
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(a) an electronic compass having x and y sense windings disposed nominally orthogonal with respect to one another; (b) means for measuring and storing as data at least one output of the sense windings provided for a known initial heading direction of said electronic compass; (c) means for measuring and storing, as data outputs of the sense windings, outputs of the sense windings provided for a number of other compass headings; (d) means for calculating at least one coordinate of the center and at least one radii of an ellipse formed by the locus of said stored outputs of each of said sense windings plotted against each other; (e) means for calculating a non-orthogonal error difference angle (φ
) between the windings by using the calculated center and radii data and the initial heading and initial output winding data; and(f) means for creating and storing a look-up table relating actual compass heading to the outputs of sense windings by using said calculated error difference angle; whereby said look-up table can be used for calibrating the electronic compass to compensate for non-orthogonal alignment of the windings. - View Dependent Claims (32, 33, 34, 35, 36)
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Specification