Bearing calculator and error correction method

• US 7,937,217 B2
• Filed: 08/02/2010
• Issued: 05/03/2011
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Okeya, Shigeo
• Primary Examiner(s): Black; Thomas G
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US12/848,831
• Publication Number:
  US 20100299093A1
• Time in Patent Office: 274 Days
• Field of Search: 701/207
• US Class Current: 701/207
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence

Abstract

A bearing calculator provided with a geomagnetic sensor for detecting earth-geomagnetism and a control unit for calculating a geographical bearing based on detection values of the geomagnetic sensor. The control unit can execute offset error correction processing for correcting the offset error to the geomagnetic sensor based on a change in the magnetic field inside the bearing calculator. When detection values of the geomagnetic sensor enter an abnormal state, it performs said offset error correction processing when the abnormal state continues for a predetermined time, while does not perform the offset error correction processing when the abnormal state ends within a predetermined time.

Claims

1. A mobile communication terminal apparatus comprising:

a geomagnetic sensor for detecting earth-geomagnetism;

a displaying means; and

a control means for calculating a geographical bearing base on values detected by the geomagnetic sensor, and displaying the resultant bearing information on the display means,

the control means

correcting the bearing information, when the detected value of the geomagnetic sensor is in a predetermined abnormal status, and the abnormal status has continued over a predetermined time, during displaying the bearing information on the display means,

displaying an information indicating that an accuracy of the bearing information is low, or an information indicating that the correction is in execution, on the display means, when the correction of the bearing information is in execution, and

displaying an information indicating that the accuracy of the bearing information is returned, or an information indicating that the correction of the bearing information has completed, on the display means, after the correction of the bearing information has completed, wherein

the geomagnetic sensor detects a plurality of earth-geomagnetism in a plurality of perpendicular directions each other,

the control means performs a detection of an offset error of the geomagnetic sensor and correction of the same, as the above correction, if at least one of the detected values of plurality of earth-geomagnetism becomes the predetermined abnormal status and the predetermined abnormal status continues over a predetermined time, and

the control means does not perform the detection of the offset error of the bearing sensor and the offset error correction processing, as the correction, if the predetermined time is not passed from when at least one of the detected values of the plurality of the earth-geomagnetism in the plurality of directions becomes the predetermined abnormal state to when all of the detected values of the earth geomagnetism in the plurality of directions is returned from the abnormal state.

2. A mobile communication terminal apparatus as set forth in claim 1, wherein the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is outside a range determined as normal.

3. A mobile communication terminal apparatus as set forth in claim 1, wherein

the geomagnetic sensor converts analog signals of the earth-geomagnetism to digital signals and outputs the same as the detected value of the earth-geomagnetism, and

the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is equal to a maximum value or a minimum value in the predetermined range.

4. A correction method for correcting an error of a geomagnetic sensor for detecting earth-geomagnetism, used in a mobile communication terminal apparatus comprising a display means for displaying a geographical bearing information calculated on the basis of a detected value of the geomagnetic sensor,

the method including:

a first step for judging an occurrence of a predetermined abnormal state of the detected value of the geomagnetic sensor, when displaying the geographical bearing information on the display means;

a second step for monitoring a state where the predetermined abnormal state continues a predetermined time from a time where the occurrence of the predetermined abnormal state is judged in the first step;

a third step for correcting the geographical bearing information when detected the predetermined abnormal state is continued for the predetermined time in the second step;

a forth step for displaying an information that an accuracy of the bearing information is low, or an information including that the correction is in execution, on the display means, when the correction of the bearing information is in execution;

a fifth step for displaying an information that the accuracy of the bearing information is returned, or an information indicating that the correction of the bearing information has completed, on the display means, after the correction of the bearing information has completed,

a sixth step for detecting a plurality of earth-geomagnetism in a plurality of perpendicular directions each other in the geomagnetic sensor,

a seventh step for performing a detection of an offset error of the geomagnetic sensor and correction of the same, as the above correction, if at least one of the detected values of plurality of earth-geomagnetism becomes the predetermined abnormal status and the predetermined abnormal status continues over a predetermined time, and

an eighth step for not performing the detection of the offset error of the bearing sensor and the offset error correction processing, as the correction, if the predetermined time is not passed from when at least one of the detected values of the plurality of the earth-geomagnetism in the plurality of directions becomes the predetermined abnormal state to when all of the detected values of the earth-geomagnetism in the plurality of directions is returned from the abnormal state.

5. A correction method as set forth in claim 4, wherein the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is outside a range determined as normal.

6. A correction method as set forth in claim 4, further including a ninth step for converting analog signals of the earth-geomagnetism to digital signals and outputs the same as the detected value of the earth-geomagnetism, and

wherein the predetermined abnormal state is a state where the detected value of the geomagnetic sensor is equal to a maximum value or a minimum value in the predetermined range.