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Automatically updating hard iron and soft iron coefficients of a magnetic sensor

  • US 9,863,867 B2
  • Filed: 02/22/2015
  • Issued: 01/09/2018
  • Est. Priority Date: 02/23/2014
  • Status: Active Grant
First Claim
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1. A method of automatically updating hard iron and soft iron coefficients of a magnetic sensor of a device, comprising:

  • measuring, by the magnetic sensor, a magnetic field during rotations of the device;

    determining by at least a criterion whether to input the measurements of the magnetic field into a coefficient estimator;

    calculating, by the coefficient estimator, new hard iron and soft iron coefficients upon receiving the measurements of the magnetic field;

    measuring an angular rotation by a gyro;

    successively measuring the magnetic field, by the magnetic sensor, while simultaneously measuring the angular rotation by the gyro, comprising;

    measuring the magnetic field while applying the existing hard and soft iron coefficients to the successive magnetic sensor measurements to generate a first rotation calculation;

    measuring the magnetic field while applying the newly calculated hard and soft iron coefficients to the successive magnetic sensor measurements to generate a second rotation calculation;

    comparing the first calculated rotation and the second calculated rotation to angular rotation measured by the gyro;

    selecting the one of the first calculated and the second calculated rotation that most closely matches the angular rotation as measured by the gyro; and

    measuring, by the magnetic sensor, the magnetic field by the magnetic sensor during rotations of the device using the newly calculated hard and soft iron coefficients when the second calculated rotation is selected.

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