NOISE PATTERN ACQUISITION DEVICE AND POSITION DETECTION APPARATUS PROVIDED THEREWITH

• US 20130218451A1
• Filed: 05/29/2012
• Published: 08/22/2013
• Est. Priority Date: 06/13/2011
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Inventors: Yamada, Kazunori
• Granted Patent: US 8,996,298 B2
• Time in Patent Office: Days
• US Class Current: 701/409
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence
• CPC Class Codes: G01C 21/08 involving use of the magnetic field of the earth
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation

Abstract

A noise pattern acquisition device includes: a geomagnetic sensor; a coordinate estimation unit configured to estimate current position coordinates; and a geomagnetic noise pattern management unit configured to, when an abnormality occurs in a magnetic field strength detected by the geomagnetic sensor during movement of the noise pattern acquisition device, store in a geomagnetic noise pattern storage unit a geomagnetic noise pattern which is a pattern representing a time-series change of the magnetic field strength detected by the geomagnetic sensor. This makes it possible to not only acquire a geomagnetic noise pattern but also detect a proper position with a simple structure and process at reduced cost.

Claims

1. A noise pattern acquisition device comprising:

a geomagnetic sensor;

a coordinate estimation unit configured to estimate current position coordinates representing a current position of the noise pattern acquisition device; and

a geomagnetic noise pattern management unit configured to, when an abnormality occurs in a magnetic field strength detected by the geomagnetic sensor during movement of the noise pattern acquisition device, store a geomagnetic noise pattern in a recording medium in association with the current position coordinates estimated by the coordinate estimation unit when the abnormality occurs, the geomagnetic noise pattern being a pattern representing a time-series change of the magnetic field strength detected by the geomagnetic sensor, the time-series change of the magnetic field strength being caused by the movement of the noise pattern acquisition device.

2. The noise pattern acquisition device according to claim 1, further comprising

a geomagnetic noise detection unit configured to detect a time period during which the pattern representing the time-series change of the magnetic field strength detected by the geomagnetic sensor during movement of the noise pattern acquisition device is different from a standard pattern, as a time period during which an abnormality occurs in the magnetic field strength, the time-series change of the magnetic field strength being caused by the movement of the noise pattern acquisition device.

3. The noise pattern acquisition device according to claim 1, further comprising

a geomagnetic noise detection unit configured to detect a time period during which an amount of change in the magnetic field strength of geomagnetism detected by the geomagnetic sensor is greater than or equal to a predetermined amount, as a time period during which an abnormality occurs in the magnetic field strength.

4. The noise pattern acquisition device according to claim 1, further comprising

a geomagnetic pattern acquisition unit configured to acquire a geomagnetic pattern that is a pattern representing a time-series change of the magnetic field strength detected by the geomagnetic sensor during movement of the noise pattern acquisition device, the time-series change of the magnetic field strength being caused by the movement of the noise pattern acquisition device.

5. The noise pattern acquisition device according to claim 1,

wherein the geomagnetic noise pattern management unit is configured to:

search the recording medium in which one or more patterns are stored, for a correction reference noise pattern that is (i) associated with coordinates near processing-target current position coordinates estimated by the coordinate estimation unit when the abnormality occurs and (ii) similar to the geomagnetic noise pattern, the processing-target current position coordinates being the current position coordinates to be processed;

store the processing-target current position coordinates and the geomagnetic noise pattern in the recording medium in association with each other when the correction reference noise pattern is not found through the search; and

instruct correction of the processing-target current position coordinates when the correction reference noise pattern is found through the search, and

the noise pattern acquisition device further comprises

a coordinate correction unit configured to correct the processing-target current position coordinates to coordinates stored in the recording medium in association with the correction reference noise pattern, according to the correction instruction by the geomagnetic noise pattern management unit.

6. A position detection apparatus comprising

the noise pattern acquisition device according to claim 5,

wherein the position detection apparatus detects a position of the position detection apparatus after movement as the current position coordinates, by estimating coordinates indicating the position of the position detection apparatus after movement.

7. The position detection apparatus according to claim 6, further comprising:

an acceleration sensor;

a posture detection unit configured to detect a posture of the position detection apparatus based on detection results of the acceleration sensor and the geomagnetic sensor; and

a movement amount detection unit configured to detect a movement amount indicating a movement direction and a movement distance of the position detection apparatus, based on the posture detected by the posture detection unit and the detection result of the acceleration sensor,

wherein the coordinate estimation unit is configured to estimate, as the current position coordinates, coordinates away from previously estimated coordinates by the movement amount detected by the movement amount detection unit.

8. The position detection apparatus according to claim 6, further comprising

an angular velocity sensor,

wherein the geomagnetic noise detection unit is configured to detect whether or not an abnormality occurs in geomagnetic detection, by comparing an amount of change in orientation of the position detection apparatus detected by the angular velocity sensor and an amount of change in orientation of the position detection apparatus derived based on a change in the magnetic field strength detected by the geomagnetic sensor.

9. The position detection apparatus according to claim 7,

wherein the movement amount detection unit is configured to further detect a movement velocity of the position detection apparatus based on the detection result of the acceleration sensor,

when searching for the correction reference noise pattern, the geomagnetic noise pattern management unit is configured to (i) scale a comparison-target pattern stored in the recording medium, according to a ratio between a movement velocity stored in the recording medium in association with the comparison-target pattern and the movement velocity detected by the movement amount detection unit when the abnormality occurs, to match a time-axis scale of the comparison-target pattern with a time-axis scale of the geomagnetic noise pattern, and (ii) perform pattern matching between the geomagnetic noise pattern and the scaled comparison-target pattern to determine whether or not the comparison-target pattern is the correction reference noise pattern, the comparison-target pattern being a pattern to be compared with the geomagnetic noise pattern, and

when the correction reference noise pattern is not found through the search, the geomagnetic noise pattern management unit is configured to store the movement velocity detected by the movement amount detection unit when the abnormality occurs, in the recording medium in association with the processing-target current position coordinates and the geomagnetic noise pattern.

10. The position detection apparatus according to claim 7,

wherein the movement amount detection unit is configured to further detect a movement velocity of the position detection apparatus based on the detection result of the acceleration sensor,

when searching for the correction reference noise pattern, the geomagnetic noise pattern management unit is configured to (i) scale the geomagnetic noise pattern according to a ratio between a predetermined movement velocity and the movement velocity detected by the movement amount detection unit when the abnormality occurs, to match a time-axis scale of the geomagnetic noise pattern with a time-axis scale of a comparison-target pattern stored in the recording medium, and (ii) perform pattern matching between the scaled geomagnetic noise pattern and the comparison-target pattern to determine whether or not the comparison-target pattern is the correction reference noise pattern, the comparison-target pattern being a pattern to be compared with the geomagnetic noise pattern, and

when the correction reference noise pattern is not found through the search, the geomagnetic noise pattern management unit is configured to store the scaled geomagnetic noise pattern in the recording medium.

11. The position detection apparatus according to claim 6,

wherein the coordinate estimation unit is further configured to calculate current position accuracy indicating accuracy of the current position coordinates, according to at least one of:

a distance of movement of the position detection apparatus from coordinates of a reference point;

complexity of the movement of the position detection apparatus from the coordinates of the reference point; and

a time period required for the movement of the position detection apparatus from the coordinates of the reference point, the reference point being a point by which the position detection apparatus has most recently passed and whose position is already identified,

when the correction reference noise pattern is not found through the search, the geomagnetic noise pattern management unit is configured to store current position accuracy calculated for the processing-target current position coordinates, in the recording medium in association with the processing-target current position coordinates and the geomagnetic noise pattern, and

when the correction reference noise pattern is found through the search, the geomagnetic noise pattern management unit is configured to (i) compare the current position accuracy calculated for the processing-target current position coordinates and accuracy stored in the recording medium in association with the correction reference noise pattern, and (ii) instruct the coordinate correction unit to correct the processing-target current position coordinates when the accuracy stored in the recording medium is higher than the current position accuracy.

12. The position detection apparatus according to claim 11,

wherein the geomagnetic noise pattern management unit is configured to replace the coordinates and the accuracy stored in the recording medium in association with the correction reference noise pattern, with the processing-target current position coordinates and the current position accuracy, respectively, when the accuracy stored in the recording medium is equal to or lower than the current position accuracy.

13. The position detection apparatus according to claim 6,

wherein the geomagnetic noise pattern management unit is configured to search for the correction reference noise pattern based on (i) a similarity between each of one or more patterns stored in the recording medium and the geomagnetic noise pattern and (ii) a distance between each set of the coordinates stored in the recording medium in association with the one or more patterns and the processing-target current position coordinates.

14. The position detection apparatus according to claim 6,

wherein when the correction reference noise pattern is found through the search, the geomagnetic noise pattern management unit is configured to store the geomagnetic noise pattern in the recording medium to associate the correction reference noise pattern and the geomagnetic noise pattern with same coordinates, and

when the geomagnetic noise detection unit detects a next geomagnetic noise pattern, the geomagnetic noise pattern management unit is configured to search the recording medium in which plural patterns are stored, for a correction reference noise pattern corresponding to the next geomagnetic noise pattern, the plural patterns including the correction reference noise pattern and the geomagnetic noise pattern which are associated with the same coordinates.

15. The position detection apparatus according to claim 6,

wherein when searching for the correction reference noise pattern, the geomagnetic noise pattern management unit is configured to specify a type of the geomagnetic noise pattern, and when the specified type indicates that the magnetic field strength is disturbed, search for a pattern stored in the recording medium in association with the type indicating the disturbance, as the correction reference noise pattern, and

when the correction reference noise pattern is not found through the search, the geomagnetic noise pattern management unit is configured to store the type indicating the disturbance in the recording medium in association with the processing-target current position coordinates and the geomagnetic noise pattern.

16. A noise pattern acquisition method to be performed by a noise pattern acquisition device, the method comprising:

estimating current position coordinates representing a current position of the noise pattern acquisition device; and

when an abnormality occurs in a magnetic field strength detected by a geomagnetic sensor during movement of the noise pattern acquisition device, storing, in a recording medium, a geomagnetic noise pattern which is a pattern representing a time-series change of the magnetic field strength detected by the geomagnetic sensor, the time-series change of the magnetic field strength being caused by the movement of the noise pattern acquisition device.

17. A non-transitory computer-readable recording medium for use in a computer, the recording medium having a computer program recorded thereon for causing the computer to acquire a noise pattern, the computer program causing the computer to execute:

estimating current position coordinates representing a current position of a noise pattern acquisition device; and

when an abnormality occurs in a magnetic field strength detected by a geomagnetic sensor during movement of the noise pattern acquisition device, storing, in a recording medium, a geomagnetic noise pattern which is a pattern representing a time-series change of the magnetic field strength detected by the geomagnetic sensor, the time-series change of the magnetic field strength being caused by the movement of the noise pattern acquisition device.

18. An integrated circuit comprising:

a coordinate estimation unit configured to estimate current position coordinates representing a current position of a noise pattern acquisition device; and

a geomagnetic noise pattern management unit configured to, when an abnormality occurs in a magnetic field strength detected by a geomagnetic sensor during movement of the noise pattern acquisition device, store, in a recording medium, a geomagnetic noise pattern which is a pattern representing a time-series change of the magnetic field strength detected by the geomagnetic sensor, the time-series change of the magnetic field strength being caused by the movement of the noise pattern acquisition device.