AZIMUTH DETECTING DEVICE AND AZIMUTH DETECTING METHOD

• US 20090088976A1
• Filed: 10/01/2008
• Published: 04/02/2009
• Est. Priority Date: 10/02/2007
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: UEDA, Akihiro, Nagamiya, Kiyomi, Maeda, Iwao, Shibata, Naoto
• Granted Patent: US 8,224,573 B2
• Time in Patent Office: Days
• US Class Current: 701/216
• CPC Class Codes: G01C 17/00 Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes using gyroscopic effect G01C19/00
• CPC Class Codes: G01S 19/45 by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement

Abstract

An azimuth detecting device mounted in a mobile object and having: a geomagnetic sensor; GPS signal receiving means; and measuring means for measuring a position of the mobile object by using a GPS signal, the azimuth detecting device being characterized in calculating a gain correction amount by means of a method of least squares, using an output value of the geomagnetic sensor when a level of the GPS signal received by the GPS signal receiving means is lower than a predetermined level, and calculating a declination correction amount and/or an inclination correction amount on the basis of information obtained from the GPS signal and correcting the output value of the geomagnetic sensor, when the level of the GPS signal is at least the predetermined level.

Claims

1. An azimuth detecting device mounted in a mobile object, comprising:

a geomagnetic sensor;

a GPS signal receiver;

a measuring part that measures a position of the mobile object by using a GPS signal; and

a controller that calculates a gain correction amount by means of a method of least squares, using an output value of the geomagnetic sensor when a level of the GPS signal received by the GPS signal receiver is lower than a predetermined level, and calculates a declination correction amount and/or an inclination correction amount on the basis of information obtained from the GPS signal, and corrects the output value of the geomagnetic sensor, when the level of the GPS signal is at least the predetermined level.

2. The azimuth detecting device according to claim 1, wherein when the level of the GPS signal is at least the predetermined level, the controller compares reliability of position information of the mobile object with reliability of speed information of the mobile object, both information being obtained based on the GPS signal, calculates the declination correction amount and/or the inclination correction amount based on the speed information when the reliability of the speed information is higher than the reliability of the position information, and calculates the declination correction amount and/or the inclination correction amount based on the position information when the reliability of the position information is higher than the reliability of the speed information.

3. An azimuth detecting device mounted in a mobile object, comprising:

a magnetic sensor;

a mobile object traveling azimuth calculation part that calculates a traveling azimuth of the mobile object on the basis of a radio wave received from a satellite;

a calculation part that calculates a geomagnetic declination and/or a geomagnetic inclination on the basis of a relationship between the traveling azimuth calculated by the mobile object traveling azimuth calculation part and an output of the geomagnetic sensor;

a correction part that corrects the output of the geomagnetic sensor by using the geomagnetic declination and/or the geomagnetic inclination calculated by the calculation part; and

an azimuth calculation part that calculates an azimuth of the mobile object on the basis of an output of the correction part.

4. The azimuth detecting device according to claim 3, wherein

when a speed of the mobile object is higher than a predetermined threshold value, the mobile object traveling azimuth calculation part calculates the traveling azimuth of the mobile object on the basis of a Doppler frequency of the radio wave received from a satellite, and

when the speed of the mobile object is lower than the predetermined threshold value, the mobile object traveling azimuth calculation part calculates the traveling azimuth of the mobile object on the basis of a difference between two positions of the mobile object that are measured at different times based on the radio wave received from the satellite.

5. An azimuth detecting method, comprising the steps of:

receiving an output value of a geomagnetic sensor;

receiving, by a GPS signal receiver, a GPS signal that is used for measuring a position of a mobile object;

calculating a gain correction amount by means of a method of least squares by using the output value of the geomagnetic sensor and correcting the output value of the geomagnetic sensor, when a level of the GPS signal is lower than a predetermined value; and

calculating a declination correction amount and/or an inclination correction amount on the basis of information received from the GPS signal to correct the output value of the geomagnetic sensor, when the level of the GPS signal is at least the predetermined level.

6. The azimuth detecting method, further comprising the steps of:

receiving an output value of a geomagnetic sensor;

calculating a traveling azimuth of a mobile object on the basis of a radio wave received from a satellite;

calculating a geomagnetic declination and/or a geomagnetic inclination on the basis of a relationship between the calculated traveling azimuth and the output value of the geomagnetic sensor;

correcting the output value of the geomagnetic sensor by using the calculated geomagnetic declination and/or the calculated geomagnetic inclination; and

calculating an azimuth of the mobile object on the basis of an output of the corrected output value of the geomagnetic sensor.