Magnetometer calibration
First Claim
1. A computer-implemented method performed by a mobile device having a magnetometer, comprising:
- receiving uncalibrated magnetometer readings;
receiving orientation data indicating a current orientation of the mobile device;
estimating calibration parameters for the magnetometer readings based on the uncalibrated magnetometer readings, the orientation data and an estimate of a magnetic field external to the mobile device, where the external magnetic field is estimated by calculating a weighted combination of a past estimate of the external magnetic field and an asymptotic mean of the external magnetic field, perturbed by random noise; and
calibrating the uncalibrated magnetometer readings using the estimated calibration parameters.
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Accused Products
Abstract
A real-time calibration system and method for a mobile device having an onboard magnetometer uses an estimator to estimate magnetometer calibration parameters and a magnetic field external to the mobile device (e.g., the earth magnetic field). The calibration parameters can be used to calibrate uncalibrated magnetometer readings output from the onboard magnetometer. The external magnetic field can be modeled as a weighted combination of a past estimate of the external magnetic field and the asymptotic mean of that magnetic field, perturbed by a random noise (e.g., Gaussian random noise). The weight can be adjusted based on a measure of the statistical uncertainty of the estimated calibration parameters and the estimated external magnetic field. The asymptotic mean of the external magnetic field can be modeled as a time average of the estimated external magnetic field. are within the scope of the following claims.
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Citations
19 Claims
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1. A computer-implemented method performed by a mobile device having a magnetometer, comprising:
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receiving uncalibrated magnetometer readings; receiving orientation data indicating a current orientation of the mobile device; estimating calibration parameters for the magnetometer readings based on the uncalibrated magnetometer readings, the orientation data and an estimate of a magnetic field external to the mobile device, where the external magnetic field is estimated by calculating a weighted combination of a past estimate of the external magnetic field and an asymptotic mean of the external magnetic field, perturbed by random noise; and calibrating the uncalibrated magnetometer readings using the estimated calibration parameters. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A magnetometer calibration system, comprising:
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a magnetometer; an angular rate sensor; a processor coupled to the magnetometer and angular rate sensor, the processor configured for executing instructions to perform operations comprising; receiving uncalibrated magnetometer readings from the magnetometer; receiving orientation data from the angular rate sensor indicating a current orientation of the mobile device; estimating calibration parameters for the magnetometer readings based on the uncalibrated magnetometer readings, the orientation data and an estimate of a magnetic field external to the mobile device, where the external magnetic field is estimated by calculating a weighted combination of a past estimate of the external magnetic field and an asymptotic mean of the external magnetic field, perturbed by random noise; and calibrating the uncalibrated magnetometer readings using the estimated calibration parameters. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification