Method and apparatus for automatic calibration of magnetic compass
First Claim
1. Apparatus for calibrating the distortions in the readings of a magnetic compass having a plurality of windings in a two dimensional plane and mounted in a vehicle comprising:
- first means coupled to the compass windings for obtaining the outputs from each of the windings as a function of time by weighting and combining the outputs from each of the windings at a first time and for a predetermined number of the next previous times to said first time to obtain a time filtered output for each of the windings;
second means coupled to said first means to form from said windings outputs measurement parameters having sensitivity values;
said sensitivity values being variables in a generalized equation that represents the configuration and location of a geometrical figure defined by the locus of coordinates of said outputs, said outputs having distortions due to permanent and induced magnetism of the vehicle and distortions due to winding imbalance between the misorientation of the magnetic compass windings;
said second means for defining calibration coefficients of said measurement parameters in said equation;
third means coupled to said second means to incorporate said measurement parameters and said calibration coefficients into a least squares matrix and to solve for said calibration coefficients;
fourth means coupled to said third means for computing calibration parameters from said calibration coefficients that are to be applied to said outputs;
fifth means coupled to said first means and said fourth means for applying said calibration parameters to said outputs from said first means to form an output from each of two windings;
said two windings being orthogonally related to one another;
sixth means coupled to said fifth means for obtaining the calibrated compass heading from said two windings outputs.
7 Assignments
0 Petitions
Accused Products
Abstract
A three winding induction compass mounted in a host vehicle has each winding output coupled to an analog to digital converter. Each winding output is weighted and accumulated by a push down stack circuit to obtain a time filtered output; the filtered outputs are mapped into equivalent two winding outputs as the vehicle is turned in a 360° circle to form sensitivity values from the windings readings and using these values to obtain measurement parameters which are incorporated into a least squares matrix which is solved for calibration coefficients to obtain the calibration parameters representing the distortions due to the permanent and inducted magnetism of the host vehicle and due to winding imbalance between the three windings and misorientation of the three windings. The calibration parameters are applied to the outputs of the three windings to obtain an equivalent two winding output which is normalized for determining the corrected compass heading.
-
Citations
21 Claims
-
1. Apparatus for calibrating the distortions in the readings of a magnetic compass having a plurality of windings in a two dimensional plane and mounted in a vehicle comprising:
-
first means coupled to the compass windings for obtaining the outputs from each of the windings as a function of time by weighting and combining the outputs from each of the windings at a first time and for a predetermined number of the next previous times to said first time to obtain a time filtered output for each of the windings; second means coupled to said first means to form from said windings outputs measurement parameters having sensitivity values;
said sensitivity values being variables in a generalized equation that represents the configuration and location of a geometrical figure defined by the locus of coordinates of said outputs, said outputs having distortions due to permanent and induced magnetism of the vehicle and distortions due to winding imbalance between the misorientation of the magnetic compass windings;said second means for defining calibration coefficients of said measurement parameters in said equation; third means coupled to said second means to incorporate said measurement parameters and said calibration coefficients into a least squares matrix and to solve for said calibration coefficients; fourth means coupled to said third means for computing calibration parameters from said calibration coefficients that are to be applied to said outputs; fifth means coupled to said first means and said fourth means for applying said calibration parameters to said outputs from said first means to form an output from each of two windings;
said two windings being orthogonally related to one another;sixth means coupled to said fifth means for obtaining the calibrated compass heading from said two windings outputs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15)
-
-
14. A method for calibrating the distortions in the readings of a magnetic compass having a plurality of windings in a two dimensional plane and mounted in a vehicle comprising the steps of:
-
a first step of obtaining the outputs from each of the windings; a second step of forming from said windings outputs measurement parameters having sensitivity values;
said sensitivity values being variables in a generalized equation that represents the configuration and location of a geometrical figure defined by the locus of coordinates of said outputs, said outputs having distortions due to permanent and induced magnetism of the vehicle and distortions due to winding imbalance between and misorientation of the magnetic compass windings;said second step defining calibration coefficients of said measurement parameters in said equation; a third step of incorporating said measurement parameters and said calibration coefficients into a least squares matrix and solving for said calibration coefficients; a fourth step of computing calibration parameters from said calibration coefficients that are to be applied to said outputs; a fifth step of applying said calibration parameters to said outputs from said first step to form an output from each of two windings;
said two windings being orthogonally related to one another;a sixth step of obtaining the calibrated compass heading from said two windings outputs. - View Dependent Claims (16, 17, 18, 19, 20)
-
-
21. Apparatus for calibrating the distortions in the readings of a magnetic compass having a plurality of windings in a two dimensional plane and mounted in a vehicle comprising:
-
first means coupled to the compass windings for obtaining the outputs from each of the windings; second means coupled to said first means to form from said windings outputs measurement parameters having sensitivity values;
said sensitivity values being variables in a generalized equation that represents the configuration and location of a geometrical figure defined by the locus of coordinates of said outputs, said outputs having distortions due to permanent and induced magnetism of the vehicle and distortions due to winding imbalance between and misorientation of the magnetic compass windings;said second means for defining calibration coefficients of said measurement parameters in said equation; third means coupled to said second means to incorporate said measurement parameters and said calibration coefficients into a least squares matrix and to solve for said calibration coefficients; fourth means coupled to said third means for computing calibration parameters from said calibration coefficients that are to be applied to said outputs; fifth means coupled to said first means and said fourth means for applying said calibration parameters to said outputs from said first means to form an output from each of two windings;
said two windings being orthogonally related to one another;sixth means coupled to said fifth means for obtaining the calibrated compass heading from said two windings outputs.
-
Specification