Calibration method for magnetic field sensing devices, corresponding system, apparatus and computer program product

A method, comprising:

• receiving signal components of a magnetic field sensing device, the signal components corresponding to an uncalibrated representation of a sensed magnetic field in a three-dimensional coordinate system;
• determining a center offset based on the received signal components;
• adjusting the signal components based on the determined center offset;
• estimating a gain of the adjusted signal components based on a difference of minimum and maximum values of the adjusted signal components;
• applying Kalman filtering to the adjusted signal components, generating a set of ellipsoid parameters, the Kalman filtering being tuned based on the estimated gain of the adjusted signal components;
• and
• generating calibrated signal components based on the determined center offset and the generated set of ellipsoid parameters, wherein the generating calibrated signal components comprises:
• translating an ellipsoid center corresponding to the ellipsoid parameters to an origin of the three-dimensional coordinate system;
• rotating axes corresponding to the ellipsoid parameters to align with axes of the three-dimensional coordinate system;
• scaling the ellipsoid parameters to define a sphere;
• and
• rotating axes of the defined sphere to align with a pre-rotation orientation of the axes corresponding to the ellipsoid parameters.

A device, comprising:

• an input, which, in operation, receives signal components of a magnetic field sensing device, the signal components corresponding to an uncalibrated representation of a sensed magnetic field in a three-dimensional coordinate system;
• and
• circuitry coupled to the input, wherein the circuitry, in operation:
• determines a center offset based on the received signal components;
• adjusts the signal components based on the determined center offset;
• estimates a gain of the adjusted signal components based on a difference of maximum and minimum values of the adjusted signal components;
• applies Kalman filtering to the adjusted signal components, generating a set of ellipsoid parameters, the Kalman filtering being tuned based on the estimated gain of the adjusted signal components;
• and
• generates calibrated signal components based on the determined center offset and the generated set of ellipsoid parameters.

A device, comprising:

• an input, which, in operation, receives signal components of a magnetic field sensing device, the signal components corresponding to an uncalibrated representation of a sensed magnetic field in a three-dimensional coordinate system;
• and
• circuitry coupled to the input, wherein the circuitry, in operation:
• determines a center offset based on the received signal components;
• adjusts the signal components based on the determined center offset;
• estimates a gain of the adjusted signal components based on a difference of maximum and minimum values of the adjusted signal components;
• applies Kalman filtering to the adjusted signal components, generating a set of ellipsoid parameters, the Kalman filtering being tuned based on the estimated gain of the adjusted signal components;
• and
• generates calibrated signal components based on the determined center offset and the generated set of ellipsoid parameters, wherein the circuitry, in operation, generates the calibrated signal components by:
• translating an ellipsoid center corresponding to the ellipsoid parameters to an origin of the three-dimensional coordinate system;
• rotating axes corresponding to the ellipsoid parameters to align with axes of the three-dimensional coordinate system;
• scaling the ellipsoid parameters to define a sphere;
• and
• rotating axes of the defined sphere to align with a pre-rotation orientation of the axes corresponding to the ellipsoid parameters.

A device, comprising:

• an input, which, in operation, receives signal components of a magnetic field sensing device, the signal components corresponding to an uncalibrated representation of a sensed magnetic field in a three-dimensional coordinate system;
• and
• circuitry coupled to the input, wherein the circuitry, in operation:
• determines a center offset based on the received signal components;
• adjusts the signal components based on the determined center offset;
• estimates a gain of the adjusted signal components based on a difference of maximum and minimum values of the adjusted signal components;
• applies Kalman filtering to the adjusted signal components, generating a set of ellipsoid parameters, the Kalman filtering being tuned based on the estimated gain of the adjusted signal components;
• and
• generates calibrated signal components based on the determined center offset and the generated set of ellipsoid parameters, wherein the circuitry, in operation:
• detects movement of the magnetic field sensing device;
• stores values of said received signal components from the magnetic field sensing device upon detecting movement of the magnetic field sensing device;
• and
• subtracts the values stored from subsequently received signal components prior to applying said Kalman filtering.

A system, comprising:

• a magnetic field sensor configured to generate signal components corresponding to an uncalibrated representation of a sensed magnetic field in a three-dimensional coordinate system;
• and
• reading circuitry coupled to the magnetic field sensor and configured to:
• determine a center offset based on received signal components;
• adjust the received signal components based on the determined center offset;
• estimate a gain of the adjusted signal components based on a difference of maximum and minimum values of the adjusted signal components;
• apply Kalman filtering to the adjusted signal components, generating a set of ellipsoid parameters, the Kalman filtering being tuned based on the estimated gain of the adjusted signal components;
• and
• generate calibrated signal components based on the determined center offset and the generated set of ellipsoid parameters, wherein the reading circuitry is configured to generate the calibrated signal components by:
• translating an ellipsoid center corresponding to the ellipsoid parameters to an origin of the three-dimensional coordinate system;
• rotating axes corresponding to the ellipsoid parameters to align with axes of the three-dimensional coordinate system;
• scaling the ellipsoid parameters to define a sphere;
• and
• rotating axes of the defined sphere to align with a pre-rotation orientation of the axes corresponding to the ellipsoid parameters.

A non-transitory computer-readable medium having contents which configure a magnetic field sensor reading device to perform a method, the method comprising:

• determining a center offset based on signal components generated by a magnetic field sensing device, the signal components corresponding to an uncalibrated representation of a sensed magnetic field in a three-dimensional coordinate system;
• adjusting the signal components based on the determined center offset;
• estimating a gain of the adjusted signal components based on a difference of maximum and minimum values of the adjusted signal components;
• applying Kalman filtering to the adjusted signal components, generating a set of ellipsoid parameters, the Kalman filtering being tuned based on the estimated gain of the adjusted signal components;
• and
• generating calibrated signal components based on the determined center offset and the generated set of ellipsoid parameters, wherein the generating the calibrated signal components includes:
• translating an ellipsoid center corresponding to the ellipsoid parameters to an origin of the three-dimensional coordinate system;
• rotating axes corresponding to the ellipsoid parameters to align with axes of the three-dimensional coordinate system;
• scaling the ellipsoid parameters to define a sphere;
• and
• rotating axes of the defined sphere to align with a pre-rotation orientation of the axes corresponding to the ellipsoid parameters.