MAGNETIC DATA PROCESSING DEVICE

Abstract

In a magnetic data processing device, an input part sequentially inputs magnetic data outputted from a two-dimensional or three-dimensional magnetic sensor. The magnetic data is two-dimensional or three-dimensional vector data that is a linear combination of a set of fundamental vectors. The magnetic data processing device stores a plurality of the inputted magnetic data as a data set of statistical population in order to update an old offset of the magnetic data with a new offset. An offset derivation part derives the new offset based on the old offset and the data set of statistical population under a constraint condition that the new offset be obtained as the sum of the old offset and a correction vector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the embodiments of the first aspect of the present invention.

FIG. 2 is a schematic diagram of the embodiments of the first aspect of the present invention.

FIG. 3 is a block diagram of the embodiments of the first aspect of the present invention.

FIG. 4 is a block diagram of the embodiments of the first aspect of the present invention.

FIG. 5 is a flow chart of the first embodiment of the first aspect of the present invention.

FIG. 6 is a schematic diagram of the first embodiment of the first aspect of the present invention.

FIG. 7 is a schematic diagram of the first embodiment of the first aspect of the present invention.

FIG. 8 is a flow chart of the second embodiment of the first aspect of the present invention.

FIG. 9 is a graph associated with the second embodiment of the first aspect of the present invention.

FIG. 10 is a graph associated with the second embodiment of the first aspect of the present invention.

FIG. 11 is a schematic diagram of the embodiments of the second aspect of the present invention.

FIG. 12 is a schematic diagram of the embodiments of the second aspect of the present invention.

FIG. 13 is a block diagram of the embodiments of the second aspect of the present invention.

FIG. 14 is a block diagram of the embodiments of the second aspect of the present invention.

FIG. 15 is a flow chart of the first embodiment of the second aspect of the present invention.

FIG. 16 is a schematic diagram of the first embodiment of the second aspect of the present invention.

FIG. 17 is a schematic diagram of the first embodiment of the second aspect of the present invention.

FIG. 18 is a flow chart of the second embodiment of the second aspect of the present invention.

Claims

1. A magnetic data processing device comprising: an input part that sequentially inputs magnetic data outputted from a two-dimensional (2D) magnetic sensor, the magnetic data being 2D vector data that is a linear combination of a set of first fundamental vectors;a storage part that stores a plurality of the inputted magnetic data as a data set of statistical population in order to update an old offset of the magnetic data with a new offset; andan offset derivation part that derives the new offset based on the old offset and the data set of statistical population under a constraint condition that the new offset be obtained as the sum of the old offset and a correction vector,where the correction vector is a linear combination of a set of second fundamental vectors defined in principle axis directions of distribution of the data set of statistical population, and respective coefficients of the linear combination of the second fundamental vectors representing the correction vector are obtained by weighting respective coefficients of a temporary position vector of a temporary offset relative to the old offset according to a ratio of principle values of the distribution of the data set of statistical population, the temporary offset being derived from the data set of statistical population without using the old offset, the temporary position vector being a linear combination of the second fundamental vectors.

2. The magnetic data processing device according to claim 1, wherein the constraint condition is that a weighting factor of the temporary position vector for the coefficient of the second fundamental vector in the principle axis direction corresponding to a smaller one of the principle values be zero if a ratio of the smaller principle value to a greater one of the principle values is equal to or less than a predetermined threshold.

3. The magnetic data processing device according to claim 1, wherein the constraint condition is that the coefficients of the correction vector be values obtained by weighting the coefficients of the temporary position vector with weighting factors which continuously correspond to the ratio of the principle values of the distribution of the data set of statistical population.

4. The magnetic data processing device according to claim 1, wherein respective weighting factors for the coefficients of the temporary position vector are normalized with reference to a weighting factor which is for the coefficient of the second fundamental vector in the principle axis direction corresponding to the greater principle value and which is set to one.

5. The magnetic data processing device according to claim 1, wherein the offset derivation part derives a value “c” that minimizes the following objective function f(c) under the constraint condition: f(c)=(Xc−j)T(Xc−j)where “X” and “j” are as follows when the magnetic data is represented by qi=(qix,qiy) (i=0,1,2, . . . ):

6. A magnetic measurement apparatus comprising: the magnetic data processing device according to claim 1; andthe 2D magnetic sensor.

7. A magnetic data processing method comprising: sequentially inputting magnetic data outputted from a two-dimensional (2D) magnetic sensor, the magnetic data being 2D vector data that is a linear combination of a set of first fundamental vectors;storing a plurality of the inputted magnetic data as a data set of statistical population in order to update an old offset of the magnetic data with a new offset; andderiving the new offset based on the old offset and the data set of statistical population under a constraint condition that the new offset be obtained as the sum of the old offset and a correction vector,where the correction vector is a linear combination of a set of second fundamental vectors defined in principle axis directions of distribution of the data set of statistical population, and respective coefficients of the linear combination of the second fundamental vectors representing the correction vector are obtained by weighting respective coefficients of a temporary position vector of a temporary offset relative to the old offset according to a ratio of principle values of the distribution of the data set of statistical population, the temporary offset being derived from the data set of statistical population without using the old offset, the temporary position vector being a linear combination of the second fundamental vectors.

8. A machine readable medium for use in a computer, the medium containing a magnetic data processing program allowing the computer to function as: an input part that sequentially inputs magnetic data outputted from a two-dimensional (2D) magnetic sensor, the magnetic data being 2D vector data that is a linear combination of a set of first fundamental vectors;a storage part that stores a plurality of the inputted magnetic data as a data set of statistical population in order to update an old offset of the magnetic data with a new offset; andan offset derivation part that derives the new offset based on the old offset and the data set of statistical population under a constraint condition that the new offset be obtained as the sum of the old offset and a correction vector,where the correction vector is a linear combination of a set of second fundamental vectors defined in principle axis directions of distribution of the data set of statistical population, and respective coefficients of the linear combination of the second fundamental vectors representing the correction vector are obtained by weighting respective coefficients of a temporary position vector of a temporary offset relative to the old offset according to a ratio of principle values of the distribution of the data set of statistical population, the temporary offset being derived from the data set of statistical population without using the old offset, the temporary position vector being a linear combination of the second fundamental vectors.

9. A magnetic data processing device comprising: an input part that sequentially inputs magnetic data outputted from a three-dimensional (3D) magnetic sensor, the magnetic data being 3D vector data that is a linear combination of a set of first fundamental vectors;a storage part that stores a plurality of the inputted magnetic data as a data set of statistical population in order to update an old offset of the magnetic data with a new offset; andan offset derivation part that derives the new offset based on the old offset and the data set of statistical population under a constraint condition that the new offset be obtained as the sum of the old offset and a correction vector,where the correction vector is a linear combination of a set of second fundamental vectors defined in principle axis directions of distribution of the data set of statistical population, and respective coefficients of the linear combination of the second fundamental vectors representing the correction vector are obtained by weighting respective coefficients of a position vector of a temporary offset relative to the old offset according to ratios of principle values of the distribution of the data set of statistical population, the temporary offset being derived from the data set of statistical population without using the old offset, the position vector of the temporary offset being a linear combination of the second fundamental vectors.

10. The magnetic data processing device according to claim 9, wherein the constraint condition is that a weighting factor of the position vector for the coefficient of one of the second fundamental vectors in one of the principle axis directions corresponding to a minimum one of the principle values be zero if a ratio of an intermediate one of the principle values to a maximum one of the principle values is higher than a first threshold and a ratio of the minimum principle value to the maximum principle value is equal to or less than a second threshold, and that respective weighting factors of the position vector for the coefficient of the second fundamental vector in the principle axis direction corresponding to the minimum principle value and the coefficient of another of the second fundamental vectors in one of the principle axis directions corresponding to the intermediate principle value be zero if the ratio of the intermediate principle value to the maximum principle value is equal to or less than the first threshold and the ratio of the minimum principle value to the maximum principle value is equal to or less than the second threshold.

11. The magnetic data processing device according to claim 9, wherein the constraint condition is that the coefficients of the correction vector be values obtained by weighting the coefficients of the position vector with weighting factors which continuously correspond to ratios of the principle values of the distribution of the data set of statistical population.

12. The magnetic data processing device according to claim 9, wherein the respective weighting factors for the coefficients of the position vector are normalized with reference to the weighting factor which is for the coefficient of the second fundamental vector in the principle axis direction corresponding to the maximum principle value and which is set to one.

13. The magnetic data processing device according to claim 9, wherein the offset derivation part derives a value “c” that minimizes the following objective function f(c) under the constraint condition: f(c)=(Xc−j)T(Xc−j)where “X” and “j” are as follows when the magnetic data is represented by qi=(qix,qiy,qiz) (i=0,1,2, . . . ):

14. A magnetic measurement apparatus comprising: the magnetic data processing device according to claim 9; andthe 3D magnetic sensor.

15. A magnetic data processing method comprising: sequentially inputting magnetic data outputted from a three-dimensional (3D) magnetic sensor, the magnetic data being 3D vector data that is a linear combination of a set of first fundamental vectors;storing a plurality of the inputted magnetic data as a data set of statistical population in order to update an old offset of the magnetic data with a new offset; andderiving the new offset based on the old offset and the data set of statistical population under a constraint condition that the new offset be obtained as the sum of the old offset and a correction vector,where the correction vector is a linear combination of a set of second fundamental vectors defined in principle axis directions of distribution of the data set of statistical population, and respective coefficients of the linear combination of the second fundamental vectors representing the correction vector are obtained by weighting respective coefficients of a position vector of a temporary offset relative to the old offset according to ratios of principle values of the distribution of the data set of statistical population, the temporary offset being derived from the data set of statistical population without using the old offset, the position vector of the temporary offset being a linear combination of the second fundamental vectors.

16. A machine readable medium for use in a computer, the medium containing a magnetic data processing program allowing the computer to function as: an input part that sequentially inputs magnetic data outputted from a three-dimensional (3D) magnetic sensor, the magnetic data being 3D vector data that is a linear combination of a set of first fundamental vectors;a storage part that stores a plurality of the inputted magnetic data as a data set of statistical population in order to update an old offset of the magnetic data with a new offset; andan offset derivation part that derives the new offset based on the old offset and the data set of statistical population under a constraint condition that the new offset be obtained as the sum of the old offset and a correction vector,where the correction vector is a linear combination of a set of second fundamental vectors defined in principle axis directions of distribution of the data set of statistical population, and respective coefficients of the linear combination of the second fundamental vectors representing the correction vector are obtained by weighting respective coefficients of a position vector of a temporary offset relative to the old offset according to ratios of principle values of the distribution of the data set of statistical population, the temporary offset being derived from the data set of statistical population without using the old offset, and the position vector of the temporary offset being a linear combination of the second fundamental vectors.