Automatic compass calibration systems and methods

• US 10,215,564 B2
• Filed: 11/13/2015
• Issued: 02/26/2019
• Est. Priority Date: 05/15/2013
• Status: Active Grant

• Current Assignee: Teledyne FLIR LLC (Teledyne Technologies Incorporated)
• Original Assignee: FLIR Systems, Inc. (Teledyne Technologies Incorporated)
• Inventors: Johnson, Mark, Mills, Warwick, Yeomans, Chris
• Primary Examiner(s): Fulton, Christopher W
• Application Number:
  US14/941,497
• Publication Number:
  US 20160069681A1
• Time in Patent Office: 1,201 Days
• Field of Search: 33356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 21/18 Stabilised platforms, e.g. by gyroscope
• CPC Class Codes: G01C 21/203 Specially adapted for sailing ships

Abstract

Techniques are disclosed for systems and methods to provide automatic and substantially continuous calibration for compasses mounted to moving structures. A compass calibration system may include a logic device configured to receive one or more sensor signals and determine a corrected magnetic field based, at least in part, on a measured local magnetic field. The logic device may be adapted to receive an angular velocity, an acceleration, the measured local magnetic field, and/or a speed of a mobile structure; generate stabilized roll and pitch components of an orientation of the mobile structure based, at least in part, on the acceleration and angular velocity; and determine the corrected magnetic field based, at least in part, on the speed, the local magnetic field, the stabilized roll and pitch components, and/or the angular velocity.

Claims

1. A system comprising:

a logic device configured to receive one or more sensor signals and determine a corrected magnetic field based, at least in part, on a measured local magnetic field, wherein the logic device is adapted to;

receive an angular velocity, an acceleration, the measured local magnetic field, and/or a speed of a mobile structure;

generate stabilized roll and pitch components of an orientation of the mobile structure based, at least in part, on the acceleration and angular velocity; and

determine the corrected magnetic field based, at least in part, on the local magnetic field and the stabilized roll and pitch components.

2. The system of claim 1, wherein:

the stabilized roll and pitch components define a stabilized horizontal plane;

the logic device is adapted to determine a heading of the mobile device based, at least in part, on a projection of the corrected magnetic field onto the stabilized horizontal plane; and

the determined heading is relatively insensitive to signal artifacts in yaw-rate components of the received angular velocity.

3. The system of claim 1, wherein the acceleration comprises a motion compensated acceleration of the mobile structure based, at least in part, on the received acceleration and/or the angular velocity.

4. The system of claim 1, wherein the angular velocity comprises a debiased angular velocity of the mobile structure based, at least in part, on the received angular velocity and/or the acceleration.

5. The system of claim 1, wherein the logic device is adapted to:

generate a raw heading based, at least in part, on the stabilized roll and pitch and/or the corrected magnetic field;

generate a corrected angular velocity of the mobile structure based, at least in part, on a debiased angular velocity of the mobile structure, the raw heading, and/or the stabilized roll and pitch; and

determine a stabilized heading based, at least in part, on the raw heading and the corrected angular velocity.

6. The system of claim 5, wherein the logic device is adapted to generate control signals for a steering actuator corresponding to a difference between a user-defined heading and the stabilized heading.

7. The system of claim 1, wherein the determining the corrected magnetic field is additionally based on the speed and/or the angular velocity, and wherein the logic device is adapted to:

determine that external conditions corresponding to the angular velocity, the acceleration, the measured local magnetic field, and/or the speed of the mobile structure are appropriate for performing a calibration process;

determine that internal conditions corresponding to a set of prior calibration points are appropriate to store a calibration point corresponding to the angular velocity, the acceleration, the measured local magnetic field, and/or the speed of the mobile structure;

store the calibration point; and

determine, from the set of prior calibration points and/or the calibration point, calibration parameters to determine the corrected magnetic field.

8. The system of claim 1, further comprising a user interface, wherein the logic device is adapted to receive user input from the user interface corresponding to a user-defined heading, and wherein the logic device is configured to display the user-defined heading and/or the corrected magnetic field using the user interface.

9. The system of claim 8, further comprising a magnetometer, wherein the logic device, the user input, and the magnetometer are implemented within a common housing.

10. The system of claim 1, wherein the mobile structure comprises a smart phone, a terrestrial robot, an aerial drone, a motorboat, a sailboat, an automobile, and/or an airplane.

11. A method comprising:

receiving an angular velocity, an acceleration, a measured local magnetic field, and/or a speed of a mobile structure;

generating stabilized roll and pitch components of an orientation of the mobile structure based, at least in part, on the acceleration and angular velocity; and

determining a corrected magnetic field based, at least in part, on the local magnetic field and the stabilized roll and pitch components.

12. The method of claim 11, wherein:

the stabilized roll and pitch components define a stabilized horizontal plane;

the method further comprises determining a heading of the mobile device based, at least in part, on a projection of the corrected magnetic field onto the stabilized horizontal plane; and

the determined heading is relatively insensitive to signal artifacts in yaw-rate components of the received angular velocity.

13. The method of claim 11, wherein the acceleration comprises a motion compensated acceleration of the mobile structure based, at least in part, on the received acceleration and/or the angular velocity.

14. The method of claim 11, wherein the angular velocity comprises a debiased angular velocity of the mobile structure based, at least in part, on the received angular velocity and/or the acceleration.

15. The method of claim 11, comprising:

generating a raw heading based, at least in part, on the stabilized roll and pitch and/or the corrected magnetic field;

generating a corrected angular velocity of the mobile structure based, at least in part, on a debiased angular velocity of the mobile structure, the raw heading, and/or the stabilized roll and pitch; and

determining a stabilized heading based, at least in part, on the raw heading and the corrected angular velocity.

16. The method of claim 15, further comprising generating control signals for a steering actuator corresponding to a difference between a user-defined heading and the stabilized heading.

17. The method of claim 11, wherein the determining the corrected magnetic field is additionally based on the speed and/or the angular velocity, the method further comprising:

determining that external conditions corresponding to the angular velocity, the acceleration, the measured local magnetic field, and/or the speed of the mobile structure are appropriate for performing a calibration process;

determining that internal conditions corresponding to a set of prior calibration points are appropriate to store a calibration point corresponding to the angular velocity, the acceleration, the measured local magnetic field, and/or the speed of the mobile structure;

storing the calibration point; and

determining, from the set of prior calibration points and/or the calibration point, calibration parameters to determine the corrected magnetic field.

18. The method of claim 11, further comprising receiving user input from a user interface corresponding to a user-defined heading, and displaying the user-defined heading and/or the corrected magnetic field using the user interface.

19. The method of claim 18, wherein the user interface is implemented within a common housing including a logic device and a magnetometer.

20. The method of claim 11, wherein the mobile structure comprises a smart phone, a terrestrial robot, an aerial drone, a motorboat, a sailboat, an automobile, and/or an airplane.