Method and apparatus for calculating azimuth

Patent metadata

Field	Value
Publication number	US-10267649-B2
Application number	US-201414243643-A
Country	US
Kind code	B2
Filing date	Apr 2, 2014
Priority date	Jul 24, 2013
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

A method and an apparatus for calculating azimuth, and a method and an apparatus for determining an offset from geomagnetic field are provided. An apparatus for calculating azimuth includes a magnetic sensor configured to sense magnetic field, a data selecting unit configured to select offset data items, an offset calculating unit configured to calculate an offset by a geometrical method that uses the selected offset data items, and an azimuth calculating unit configured to calculate an azimuth by using the calculated offset.

First claim

What is claimed is:

1. An apparatus comprising:
a magnetic sensor configured to sense a magnetic field and convert the sensed magnetic field into a voltage;
an amplifier configured to amplify the voltage;
an analog-to-digital converter configured to convert the amplified voltage into voltage data; and
a processor configured to execute instructions stored in a memory, thereby configuring the processor to:
separate the voltage data into 3-axis magnetic field components in X, Y and Z axes to generate separated voltage data;
remove noise components of the separated voltage data by creating a median value of the separated voltage data and filtering the separated voltage data by selecting midmost voltage data;
apply a previously calculated offset to the filtered separated voltage data;
determine, based on the application of the previously calculated offset, whether the filtered separated voltage data correspond to a geomagnetic field;
selectively, based on a result of the determining of whether the filtered separated voltage data correspond to the geomagnetic field,
select offset data items from the filtered separated voltage data,
subtract a difference between the filtered separated voltage data and previously measured voltage data from a previous offset reference point,
set a resultant value as a new offset reference point, in response to the filtered separated voltage data being determined not to correspond to the geomagnetic field and the previously measured voltage data being determined to correspond to the geomagnetic field, and
calculate an offset by a geometrical method that uses the selected offset data items and the new offset reference point; and

determine a location or directional information of the apparatus based on the voltage data for the sensed magnetic field and selectively one of the calculated offset and the previously calculated offset, with increased location or directional determination speed and/or accuracy with respect to a presence of an abnormal magnetic field.

2. The apparatus according to claim 1 , wherein the processor is further configured, through the execution of the instructions, to remove an instantaneous noise from measurements of the magnetic field.

3. The apparatus according to claim 1 , wherein the processor is further configured, through the execution of the instructions, to select at least three data items as the selected offset data items, including two distant X or Y axis voltage data items and an X or Y voltage data item between the two distant voltage data items.

4. The apparatus according to claim 3 , wherein the processor is further configured, through the execution of the instructions, to use two values, which are a value having the greatest difference in distance between data items in a measured data group and a value having the second greatest difference, as main-calculation data items, and
wherein, when arranged in order of X values, a data item between the two values is used as sub-calculation data.

5. The apparatus according to claim 4 , wherein the processor is further configured, through the execution of the instructions, to set one point that is farther from the sub-calculation data, among intersecting points of two circles having the two main-calculation data items as centers and each having a radius r, as the calculated offset.

6. The apparatus according to claim 1 ,
wherein the determining of the location or directional information of the apparatus includes, based on a result of the determining of whether the filtered separated voltage data correspond to the geomagnetic field,
determining the location or directional information based on the previously calculated offset, without performing the selecting of the offset data items, the subtracting of the difference, the setting of the resultant value, and the calculating of the offset, in response to determining that the magnetic field is the geomagnetic field, and
determining the location or directional information based on the calculated offset in response to determining that the magnetic field is not the geomagnetic field.

7. The apparatus according to claim 1 , wherein the filtered separated voltage data that is presently measured is represented as C 1 (X c , Y c ) and the filtered separated voltage data which is previously measured is represented as P 1 (X p , Y p ), and in response to a determination that the P 1 is the geomagnetic field and the C 1 is not the geomagnetic field, the processor is controlled to subtracts a difference between the C 1 (X c , Y c ) and the P 1 (X p , Y p ) from the previously calculated offset and set a resultant value as the new offset reference point.

8. The apparatus according to claim 1 , wherein the determination of whether the filtered separated voltage data correspond to the geomagnetic field is based on consideration of a dip angle with respect to the Z axis in the XY plane and magnitudes of the magnetic field in the X, Y, and Z axes.

9. A processor-implemented method of determining a location or directional information of an apparatus comprising a magnetic sensor, an amplifier, an analog-to-digital converter, and a processor, the method comprising:
sensing, using the magnetic sensor, a magnetic field and converting the sensed magnetic field into a voltage;
amplifying, using the amplifier, the voltage;
converting, using the analog-to-digital converter, the amplified voltage into voltage data;
controlling, through execution by a processor of instructions stored in a memory, the processor to:
separate the voltage data into 3-axis magnetic field components in X, Y and Z axes to generate separated voltage data;
remove noise components of the separated voltage data by creating a median value of the separated voltage data and filtering the separated voltage data by selecting midmost voltage data;
apply a previously calculated offset to the filtered separated voltage data;
determine, based on the application of the previously calculated offset, whether the filtered separated voltage data correspond to a geomagnetic field;
selectively, based on a result of the determining of whether the filtered separated voltage data correspond to the geomagnetic field,
select offset data from the filtered separated voltage data which do not correspond to the geomagnetic field,
subtract a difference between the filtered separated voltage data and previously measured voltage data from the previously calculated offset and setting a resultant value as a new offset reference point, in response to the previously measured voltage data being determined to correspond to the geomagnetic field, and
calculate an offset by using the selected offset data and the new offset reference point; and

determine a location or directional information of the apparatus based on the voltage data for the sensed magnetic field and selectively one of the calculated offset, another calculated offset, and the previously calculated offset, with increased location or directional determination speed and/or accuracy with respect to a presence of an abnormal magnetic field,
wherein, when the filtered separated voltage data does not correspond to the geomagnetic field, the location or directional information of the apparatus is determined based on the voltage data for the sensed magnetic field and the calculated offset in response to a determination that the calculated offset is within a set range of a reference point, and determined based on the voltage data for the sensed magnetic field and the other calculated offset, calculated by a geometrical method that uses the previously calculated offset, in response to a determination that the calculated offset is outside the set range of the reference point.

Assignees

• Magnachip Semiconductor Ltd

Inventors

• Kim Dong Ho
• Cho Ki Seok

Classifications

• G01C17/30 Primary

  Earth-inductor compasses · CPC title

• G01C25/00 Primary

  Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass (testing, calibrating or compensating compasses G01C17/38) · CPC title

• G01C17/28

  Electromagnetic compasses (with north seeking magnetic elements and having electric pick-offs G01C17/26) · CPC title

• G01C17/38 Primary

  Testing, calibrating, or compensating of compasses · CPC title