Method and system to detect an orientation of a moving object

• US 7,225,552 B2
• Filed: 08/16/2005
• Issued: 06/05/2007
• Est. Priority Date: 01/14/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Shim, Young Bo, Roh, Kyung Shik, Kwon, Woong, Han, Woo Sup
• Primary Examiner(s): Fulton; Christopher W.
• Application Number:
  US11/204,347
• Publication Number:
  US 20060156564A1
• Time in Patent Office: 658 Days
• Field of Search: 333/55.R, 333/56, 333/57
• US Class Current: 33/356
• CPC Class Codes: G01C 17/02 Magnetic compasses
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38

Abstract

Method and system to detect orientations of a moving object using one or more magnetic compasses. The method and system minimize magnetic field interference in a space where an object is moving such that the orientations of the moving object can be precisely detected. The method includes setting one or more earth magnetic field (EMF) conditions without a magnetic field interference component to determine whether the one or more magnetic compasses are located in an EMF area, calculating a magnitude of a magnetic field applied to the moving object using the one or more magnetic field compasses, and detecting an orientation of the moving object by determining whether the calculated magnitude of the magnetic field satisfies the one or more EMF conditions.

Claims

1. A method of detecting an orientation of a moving object on which one or more magnetic compasses are installed, the method comprising:

setting one or more earth magnetic field (EMF) conditions without a magnetic field interference component to determine whether the one or more magnetic compasses are located in an EMF area;

calculating a magnitude of a magnetic field applied to the moving object using the one or more magnetic compasses; and

detecting an orientation of the moving object by determining whether the calculated magnitude of the magnetic field satisfies the one or more EMF conditions.

2. The method as set forth in claim 1, wherein the setting of the one or more EMF conditions comprises:

obtaining trajectories of a horizontal component H_x and a vertical component H_y of a plurality of magnetic fields by rotating the one or more magnetic compasses in a plurality of corresponding positions in the EMF area;

obtaining one or more parameters to approximate the trajectories as a sinusoidal curve; and

calculating the one or more EMF conditions by obtaining upper and lower limits of the one or more parameters.

3. The method as set forth in claim 2, wherein the one or more parameters include amplitudes of the approximated sinusoidal curve.

4. The method as set forth in claim 2, wherein the one or more EMF conditions include a plurality of EMF conditions, and if the plurality of EMF conditions are satisfied by the calculated magnitude of the magnetic field, data of the one or more magnetic compasses are determined to be valid and then the orientation of the moving object is determined.

5. The method as set forth in claim 4, wherein the one or more magnetic compasses include two or more magnetic compasses.

6. The method as set forth in claim 4, wherein the data of the one or more magnetic compasses is determined to be invalid if any one of the plurality of EMF conditions is not satisfied.

7. The method as set forth in claim 4, wherein the plurality of EMF conditions comprises a first condition set to be compared to azimuths of the one or more magnetic compasses and magnitudes of the magnetic fields of the one or more magnetic compasses and defined by the following equation (1), and a second condition set to be compared to a difference between magnitudes of the one or more magnetic compasses and defined by the following equation (2),

(ψ

_l++ψ

_l−

cos 2θ

)/2≦

|H|²/|H_E|²≦

(ψ

_u++ψ

_u−

cos 2θ

)/2 

 

(1)

wherein, ψ

_l+≡

ψ

_xl+ψ

_yl,ψ

_u+≡

ψ

_xu+ψ

_yu and ψ

_l−

≡

min(ψ

_yl−

ψ

_xl,ψ

_yu−

ψ

_xu),ψ

_l+≡

max(ψ

_yl−

ψ

_xl,ψ

_yu−

ψ

_xu), and θ

is an azimuth measurement value,

( ψ

_l++ ψ

_l−

cos 2θ

)/2≦

(|¹H|²−

|²H|²)/|H_E|²≦

( ψ

_u++ ψ

_u−

cos 2θ

)/2 

 

(2)

where, ψ

_l+≡

min(¹ψ

_x−

²ψ

_x)+min(¹ψ

_y−

²ψ

_y), ψ

_u+≡

max(¹ψ

_x−

²ψ

_x)+max(¹ψ

_y−

²ψ

_y), ψ

_l−

≡

min(¹ψ

_y−

²ψ

_y−

¹ψ

_x+²ψ

_x), and ψ

_u−

≡

max(¹ψ

_y−

²ψ

_y−

¹ψ

_x+²ψ

_x), and θ

is the azimuth measurement value.

8. The method as set forth in claim 1, wherein the magnitude of the calculated magnetic field is obtained by the following equation (3) using the one or more magnetic compasses

$\begin{array}{c}{}^{}\end{array}$

H 

2 = ( r x - O x A ^ x ⨯



H E 

) 2 + ( r y - O y A ^ y ⨯



H E 

) 2 , ( 3 )

where, Â

_x and Â

_y are amplitude values, O_x, and O_y, are offset values, r_x, and r_y are raw data values of the one or more magnetic compasses, and |H_E| denotes magnitude of the earth'"'"'s magnetic field.

9. A method of detecting an orientation of a moving object, the method comprising:

collecting calibration magnetic field data from a plurality of locations in an earth magnetic field (EMF) area; and

characterizing the collected calibration magnetic field data and setting one or more rules to define when the moving object is in the EMF area according to a current magnetic field data.

10. The method as set forth in claim 9, wherein the EMF area comprises at least one space having minimal or no magnetic field interference, and the collecting of the calibration magnetic field data comprises:

estimating the plurality of locations in the EMF area;

calculating a plurality of magnetic fields at the plurality of locations in the EMF area;

determining a plurality of calibration parameters that correspond with the plurality of magnetic fields; and

selecting ones of the plurality of calibration parameters that are determined to approximate the earth'"'"'s magnetic field to set the one or more rules accordingly.

11. The method as set forth in claim 9, further comprising:

collecting current magnetic field data about a first magnetic field with a first compass disposed on the moving object;

collecting current magnetic field data about a second magnetic field with a second compass disposed on the moving object;

determining whether the current magnetic field data of the first and second magnetic fields satisfy the one or more rules; and

detecting the orientation of the moving object according to the current magnetic field data of the first and second magnetic fields when it is determined that the current magnetic field data of the first and second magnetic fields satisfy the one or more rules.

12. The method as set forth in claim 11, wherein the characterizing of the collected magnetic field data and the setting of the one or more rules comprises:

creating a first rule to be satisfied by the magnetic field data of both the first and second magnetic fields; and

creating a second rule to be satisfied by a difference between the magnetic field data of the first and second magnetic fields.

13. The method as set forth in claim 11, wherein the detecting of the orientation further comprises setting an azimuth of one of the first and second compasses as the orientation of the moving object.

14. A method of detecting an orientation of a moving object, the method comprising:

collecting magnetic field data at a present location of the moving object;

determining whether the collected magnetic field data satisfies one or more predetermined rules that define when the moving object is in an earth magnetic field (EMF) area; and

detecting the orientation of the moving object according to the collected magnetic field data when the collected magnetic field data satisfies the one or more predetermined rules.

15. A system to detect orientations of a moving object on which one or more magnetic compasses are installed, comprising:

a magnetic field condition setting unit to set one or more conditions of an earth magnetic field (EMF) without a magnetic field interference component to determine whether the one or more magnetic compasses are located in an EMF area;

a magnetic field calculation unit to calculate a magnitude of a magnetic field applied to the moving object using the one or more magnetic compasses;

an earth magnetic field area determination unit to determine whether the calculated magnitude of the magnetic field satisfies the one or more EMF conditions and to determine whether a position of the moving object is in the EMF area; and

an orientation determining unit to determine an orientation of the moving object based on one or more azimuths of the one or more magnetic compasses if the position of the moving object corresponds to the EMF area.

16. The system as set forth in claim 15, wherein the magnetic field condition setting unit comprises:

a candidate position selection unit to select one or more candidate positions in which corresponding magnetic fields have little or no magnetic field interference component;

a raw data acquisition unit to obtain one or more parameters by obtaining a raw data trajectory of the corresponding magnetic fields having a horizontal component H_x and a vertical component H_y by rotating the one or more magnetic compasses at the one or more selected candidate positions;

a candidate position determination unit to determine a current compass position as a candidate position that satisfy the one or more EMF conditions when the corresponding trajectory of raw data approximates a sinusoidal wave and to generate a candidate position group based on a result of the determination; and

a condition acquisition unit to determine upper and lower limits obtained at each candidate position in the candidate position group and to determine the one or more EMF conditions.

17. The system as set forth in claim 16, wherein the candidate position determination unit compares amplitudes and offsets at each of the one or more selected candidate positions with one and another and excludes one or more candidate positions having outlier points from the candidate position group based on a result of the comparison.

18. The system as set forth in claim 15, wherein the one or more magnetic compasses include two or more magnetic compasses.

19. The system as set forth in claim 15, wherein the one or more EMF conditions include a plurality of EMF conditions, and the EMF area determination unit determines that the position of the moving object corresponds to the EMF area without the magnetic field interference component if the magnitude of the magnetic field satisfies all of the plurality of EMF conditions, and determines that the position of the moving object does not correspond to the EMF area if the magnitude of the magnetic field fails to satisfy any one of the plurality of EMF conditions.

20. A system to detect an orientation of a moving object, comprising:

a magnetic field calculation unit to collect calibration magnetic field data from a plurality of locations in an earth magnetic field (EMF) area; and

a magnetic field condition setting unit to characterize the collected calibration magnetic field data and to set one or more rules to define when the moving object is in the EMF area according to a current magnetic field data.

21. The system as set forth in claim 20, wherein the magnetic field calculation unit collects current magnetic field data about a first magnetic field with a first compass disposed on the moving object and collects current magnetic field data about a second magnetic field with a second compass disposed on the moving object, and the system further comprises:

an earth magnetic field area determination unit to determine whether the current magnetic field data of the first and second magnetic fields satisfy the set one or more rules; and

an orientation determination unit to determine the orientation of the moving object according to the current magnetic field data of the first and second magnetic fields when it is determined that the current magnetic field data of the first and second magnetic fields satisfy the set one or more rules.

22. A system to detect an orientation of a moving object, comprising:

a magnetic field calculation unit to collect magnetic field data at a present location of the moving object;

a magnetic field comparison unit to determine whether the collected magnetic field data satisfies one or more predetermined rules that define when the moving object is in an earth magnetic field (EMF) area; and

an orientation determination unit to detect the orientation of the moving object according to the collected magnetic field data when the collected magnetic field data satisfies the one or more predetermined rules.