Magnetic sensor control device

• US 7,418,359 B2
• Filed: 10/10/2006
• Issued: 08/26/2008
• Est. Priority Date: 10/11/2005
• Status: Expired due to Fees

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Handa, Ibuki
• Primary Examiner(s): Nghiem; Michael P.
• Assistant Examiner(s): Le; Toan M
• Application Number:
  US11/548,022
• Publication Number:
  US 20070086103A1
• Time in Patent Office: 686 Days
• Field of Search: 702/104, 702/87, 702/92, 702/95, 702/85, 73/14.1, 324/202, 324/207.11, 324/226, 324/244, 324/260, 333/55.R, 333/56, 701/224
• US Class Current: 702/104
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A magnetic sensor control device has an input section, a selection section, a calculation section, and a setting section. The input section inputs a plurality of magnetic data each having 3 components sequentially output from a 3-dimensional (3D) magnetic sensor. The selection section selects 4 magnetic data satisfying a predetermined 4-point selection condition from the plurality of the input magnetic data. The calculation section calculates a center point equally distant from 4 points corresponding to the 4 selected magnetic data. The setting section sets 3 components representing the center point as an offset of the magnetic data.

Claims

1. A magnetic sensor control device comprising:

an input section that input a plurality of magnetic data having 2 components sequentially output from a 2-dimensional (2D) magnetic sensor;

a buffer that stores the plurality of magnetic data;

a selection section that selects 3 magnetic data satisfying a predetermined 3-point selection condition from the plurality of the stored magnetic data;

wherein, when new magnetic data is stored in the buffer, the selection section selects one of 3 data structures provided for storing 3 magnetic data as candidates for selection, and updates the selected data structure with the new magnetic data stored in the buffer, provided that the length of a chord of a circular arc passing through 3 points corresponding to the 3 magnetic data stored in the 3 data structures is increased or at least is not decreased by updating the one data structure, in which magnetic data corresponding to one of the two points at both ends of the circular arc is stored, with the new magnetic data stored in the buffer, such that the 3 data structures store first magnetic data and second magnetic data which correspond to two points at both ends of the circular arc and one of which is the new magnetic data;

wherein, when new magnetic data is stored in the buffer, the selection section obtains magnetic data which has not been selected as any candidate for selection of the first and second magnetic data corresponding to the two points at both ends of the circular arc, and sets the obtained magnetic data as a candidate for selection of third magnetic data of an intermediate point of the circular arc, and

wherein the selection section determines whether or not a set of the first, second and third magnetic data satisfies the predetermined 3-point selection condition;

a calculation section that calculates a center point equally distant from 3 points each represented by 2 components of a corresponding one of the 3 selected magnetic data; and

a setting section that sets 2 components representing the center point as an offset of the magnetic data.

2. The magnetic sensor control device according to claim 1, wherein the 3-point selection condition includes a triangle condition associated with distortion of a concerned triangle relative to a regular triangle, the concerned triangle having vertices specified by 3 points corresponding to the 3 magnetic data stored in the data structures.

3. The magnetic sensor control device according to claim 2, wherein the triangle condition includes a condition that variation between inner angles of the concerned triangle is within a predetermine range.

4. The magnetic sensor control device according to claim 2, wherein the triangle condition includes a condition that variation between lengths of sides of the concerned triangle is within a predetermined range.

5. The magnetic sensor control device according to claim 2, wherein the triangle condition includes a condition that variation between distances of vertices of the concerned triangle from a centroid of the concerned triangle is within a predetermined range.

6. A magnetic sensor control device, comprising:

an input section that inputs a plurality of magnetic data having 2 components sequentially output from a 2-dimensional (2D) magnetic sensor;

a selection section that selects 3 magnetic data satisfying a predetermined 3-point selection condition from the plurality of the input magnetic data,

wherein the 3-point selection condition includes a triangle condition associated with distortion of a concerned triangle relative to a regular triangle, the concerned triangle having vertices specified by 3 points corresponding to the 3 magnetic data stored in the data structures, and

wherein the triangle condition includes a condition that the ratio of a minimum eigenvalue of a symmetric matrix A of 2 rows and 2 columns expressed as follows to a maximum eigenvalue of the symmetric matrix A is equal to or higher than a predetermined value;

$A=\underset{i=0}{\overset{2}{\sum <br><br>}}<br><br>\left(p_i-d_3\right)<br><br>{\left(p_i-d_3\right)}^T,$

where pi (i=0, 1,2) denotes each vertex of the concerned triangle, and d₃ denotes a centroid of the concerned triangle;

a calculation section that calculates a center point equally distant from 3 points each represented by 2 components of a corresponding one of the 3 selected magnetic data; and

a setting section that sets 2 components representing the center point as an offset of the magnetic data.

7. The magnetic sensor control device according to claim 6, wherein the selection section applies the triangle condition to a plurality of combinations of the input magnetic data to calculate respective values of the ratio for the respective triangles, and selects 3 points which represent one of the plurality of the triangles having a maximal value of the ratio.

8. The magnetic sensor control device according to claim 7, further comprising:

a progress value output section that outputs a value of the ratio or a progress value derived based on the ratio, indicating a progress state of selection of the 3 magnetic data satisfying the 3-point selection condition until the selection is completed after the selection is initiated.

9. The magnetic sensor control device according to claim 8, wherein the progress value represents an angle corresponding to a central angle of the circular arc passing through the 3 points corresponding to the 3 magnetic data stored in the 3 data structures.

10. A magnetic measurement apparatus comprising:

a 2-dimensional (2D) magnetic sensor that sequentially outputs a plurality of magnetic data each having 2 components;

an input section that inputs the plurality of the magnetic data having 2 components sequentially output from the 2-dimensional (2D) magnetic sensor;

a buffer that stores the plurality of the input magnetic data;

a selection section that selects 3 magnetic data satisfying a predetermined 3-point selection condition from the plurality of the stored magnetic data;

wherein, when new magnetic data is stored in the buffer, the selection section selects one of 3 data structure provided for storing 3 magnetic data as candidates for selection, and updates the selected data structure with the new magnetic data stored in the buffer, provided that the length of a chord of a circular arc passing through 3 points corresponding to the 3 magnetic data stored in the 3 data structures is increased or at least is not decreased by updating the one data structure, in which magnetic data corresponding to one of two points at both ends of the circular arc is stored, with the new magnetic data stored in the buffer, such that the 3 data structures store first magnetic data and second magnetic data which correspond to two points at both ends of the circular arc and one of which is the new magnetic data;

wherein, when new magnetic data is stored in the buffer, the selection section obtains magnetic data which has not been selected as any candidate for selection of the first and second magnetic data corresponding to the two points at both the ends of the circular arc, and sets the obtained magnetic data as a candidate for selection of third magnetic data of an intermediate point of the circular arc, and

wherein the selection section determines whether or not a set of the first, second and third magnetic data satisfies the predetermined 3-point selection condition;

a calculation section that calculates a center point equally distant from 3 points each represented by 2 components of a corresponding one of the 3 selected magnetic data; and

a setting section that sets 2 components representing the center point as an offset of the magnetic data.

11. The magnetic measurement apparatus according to claim 10, wherein the selection section sequentially applies the 3-point selection condition to a plurality of triangles corresponding to a plurality of combinations of the input magnetic data so as to find a optimum triangle which best satisfies the 3-point selection condition, the apparatus further comprising a display section that allows the user to view a progress state of operation of the selection section.

12. A magnetic measurement apparatus, comprising:

a 2-dimensional (2D) magnetic sensor that sequentially outputs a plurality of magnetic data each having 2 components;

an input section that inputs the plurality of the magnetic data having 2 components sequentially output from the 2-dimensional (2D) magnetic sensor;

a selection section that selects 3 magnetic data satisfying a predetermined 3-point selection condition from the plurality of the input magnetic data, wherein the selection section sequentially applies the 3-point selection condition to a plurality of triangles corresponding to a plurality of combinations of the input magnetic data so as to find a optimum triangle which best satisfies the 3-point selection condition,

a notification section that notifies a user of a progress state of operation of the selection section by generating a sound of a music note varying depending on the progress state;

a calculation section that calculates a center point equally distant from 3 points each represented by 2 components of a corresponding one of the 3 selected magnetic data; and

a setting section that sets 2 components representing the center point as an offset of the magnetic data.

13. An offset setting method for magnetic sensors, the method comprising:

inputting a plurality of magnetic data each having 2 components sequentially output from a 2-dimensional (2D) magnetic sensor;

storing the plurality of the input magnetic data in the buffer;

selecting 3 magnetic data satisfying a predetermined 3-point selection condition from the plurality of the stored magnetic data;

wherein, when new magnetic data is stored in the buffer, the step of selecting selects one of 3 data structures provided for storing 3 magnetic data as candidates for selection, and updates the selected data structure with the new magnetic data stored in the buffer, provided that the length of a chord of a circular arc passing through 3 points corresponding to the 3 magnetic data stored in the 3 data structures is increased or at least is not decreased by updating the one data structure, in which magnetic data corresponding to one of two points at both ends of the circular arc is stored, with the new magnetic data stored in the buffer, such that the 3 data structures store first magnetic data and second magnetic data which correspond to two points at both ends of the circular arc and one of which is the new magnetic data;

wherein, when new magnetic data is stored in the buffer, the step of selecting obtains magnetic data which has not been selected as any candidate for selection of the first and second magnetic data corresponding to the two points at both ends of the circular arc, and sets the obtained magnetic data as a candidate for selection of third magnetic data of an intermediate point of the circular arc; and

wherein the step of selecting determines whether or not a set of the first, second or third magnetic data satisfies the predetermined 3-point selection condition;

calculating a center point equally distant from 3 points each represented by 2 components of a corresponding one of the 3 selected magnetic data; and

setting 2 components of the center point as an offset of the magnetic data.

14. A machine readable medium containing an offset setting program for magnetic sensors, the program being executable by a computer to perform a method comprising:

inputting a plurality of magnetic data each having 2 components sequentially output from a 2-dimensional (2D) magnetic sensor;

storing the plurality of the input magnetic data in the buffer

selecting 3 magnetic data satisfying a predetermined 3-point selection condition from the plurality of the stored magnetic data;

wherein, when new magnetic data is stored in the buffer, the step of selecting selects one of 3 data structures provided for storing 3 magnetic data as candidates for selection, and updates the selected data structure with the new magnetic data stored in the buffer, provided that the length of a chord of a circular arc passing through 3 points corresponding to the 3 magnetic data stored in the 3 data structures is increased or at least is not decreased by updating the one data structure, in which magnetic data corresponding to one of two points at both ends of the circular arc is stored, with the new magnetic data stored in the buffer, such that the 3 data structures store first magnetic data and second magnetic data which correspond to two points at both ends of the circular arc and one of which is the new magnetic data;

wherein, when new magnetic data is stored in the buffer, the step of selecting obtains magnetic data which has not been selected as any candidate for selection of the first and second magnetic data corresponding to the two points at both ends of the circular arc, and sets the obtained magnetic data as a candidate for selection of third magnetic data of an intermediate point of the circular arc, and

wherein the step of selecting determines whether or not a set of the first, second and third magnetic data satisfies the predetermined 3-point selection condition;

calculating a center point equally distant from 3 points each represented by 2 components of a corresponding one of the 3 selected magnetic data; and

setting 2 components of the center point as an offset of the magnetic data.