PROCESSES FOR MORE ACCURATELY CALIBRATING AND OPERATING E-COMPASS FOR TILT ERROR, CIRCUITS, AND SYSTEMS

• US 20090254294A1
• Filed: 03/05/2009
• Published: 10/08/2009
• Est. Priority Date: 03/06/2008
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Dutta, Goutam
• Granted Patent: US 9,062,971 B2
• Time in Patent Office: Days
• US Class Current: 702/92
• CPC Class Codes: G01C 17/02 Magnetic compasses
• CPC Class Codes: G01C 17/28 Electromagnetic compasses with north seeking magnetic elements and having electric pick-offs G01C17/26
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

An electronic circuit includes an electronic compass (e-compass 1150) having e-compass sensors (X, Y, Z) mounted on different axes and operable to supply e-compass sensor data, memory circuitry (1024), and an electronic processor (1030) coupled to said e-compass sensors (1150, X, Y, Z) and to said memory circuitry (1024), said electronic processor (1030) operable to execute an electronic ellipse-fitting procedure responsive to the e-compass sensor data to generate at least one signal related to an ellipse tilt angle (ξ), and store the at least one signal in said memory circuitry (1024) as a tilt calibration parameter for the e-compass. Processes for calibrating an e-compass, as well as electronic circuits and processes for correcting measured heading, and processes of manufacture are also disclosed.

Claims

1. An electronic circuit comprising:

an e-compass having e-compass sensors mounted on different axes and operable to supply e-compass sensor data;

memory circuitry; and

an electronic processor coupled to said e-compass sensors and to said memory circuitry, said electronic processor operable to execute an electronic ellipse-fitting procedure responsive to the e-compass sensor data to generate at least one signal related to an ellipse tilt angle, and store the at least one signal in said memory circuitry as a tilt calibration parameter for the e-compass.

2. The electronic circuit claimed in claim 1 further comprising a tilt sensor coupled to supply tilt sensor data to said electronic processor.

3. The electronic circuit claimed in claim 2 wherein said electronic processor is operable in response to the tilt sensor data to execute a coarse detilting procedure on the e-compass sensor data.

4. The electronic circuit claimed in claim 3 wherein said electronic processor is operable to generate the at least one signal related to the ellipse tilt angle fitted to the e-compass sensor data as processed by the coarse detilting procedure.

5. The electronic circuit claimed in claim 2 wherein said tilt sensor includes an accelerometer.

6. The electronic circuit claimed in claim 1 wherein said processor is further operable to generate a second signal representing a hard iron calibration parameter responsive to the e-compass sensor data and the tilt calibration parameter.

7. An electronic circuit comprising:

an e-compass oriented with a heading and having e-compass sensors mounted on different axes and operable to supply e-compass sensor data;

memory circuitry holding a tilt angle e-compass calibration parameter; and

an electronic processor coupled to said e-compass sensors and to said memory circuitry, said electronic processor responsive to the e-compass sensor data and the tilt angle e-compass calibration parameter to generate at least one signal representing a measured heading of the e-compass corrected using the tilt angle e-compass calibration parameter.

8. The electronic circuit claimed in claim 7 further comprising a tilt sensor coupled to supply tilt sensor data to said electronic processor.

9. The electronic circuit claimed in claim 8 wherein said electronic processor is operable in response to the tilt sensor data to execute a coarse detilting procedure on the e-compass sensor data.

10. The electronic circuit claimed in claim 9 wherein said electronic processor is operable to apply the residual tilt angle e-compass calibration parameter to the e-compass sensor data as processed by the coarse detilting procedure.

11. The electronic circuit claimed in claim 8 wherein said tilt sensor includes an accelerometer.

12. The electronic circuit claimed in claim 11 wherein said processor is operable to generate at least one signal representing position in response to said accelerometer and said e-compass sensor data.

13. The electronic circuit claimed in claim 7 wherein said memory circuitry holds instructions for processing the e-compass sensor data and the residual tilt angle e-compass calibration parameter to generate the at least one signal representing the corrected measured heading of the e-compass.

14. The electronic circuit claimed in claim 7 further comprising decoding circuitry for decoding satellite positioning signals, said processor coupled to said decoding circuitry and operable to generate at least one signal representing position in response to said decoding circuitry and said e-compass sensor data.

15. A calibration process for an e-compass with sensors, the calibration process comprising executing an electronic ellipse-fitting procedure responsive to data from the e-compass sensors to generate at least one signal related to an ellipse tilt angle for use as a tilt calibration parameter for the e-compass.

16. The calibration process claimed in claim 15 further comprising performing a coarse detilting procedure on the e-compass sensor data using tilt sensor data and then executing the electronic ellipse-fitting procedure on the coarsely-detilted e-compass sensor data to generate a signal related to the ellipse tilt angle for use as the tilt calibration parameter for the e-compass.

17. A measuring process for measuring heading of an e-compass having sensors, the measuring process comprising utilizing e-compass sensor data and a tilt angle e-compass calibration parameter to generate at least one signal representing a measured heading of the e-compass corrected using the tilt angle e-compass calibration parameter.

18. The measuring process claimed in claim 17 further comprising performing a coarse detilting procedure on the e-compass sensor data using tilt sensor data and then applying the residual tilt angle e-compass calibration parameter to the e-compass sensor data as processed by the coarse detilting procedure to generate the at least one signal representing a measured heading of the e-compass corrected using the tilt angle e-compass calibration parameter.

19. A portable electronic device oriented with a heading to be measured, the device comprising:

an e-compass having e-compass sensors mounted on different axes and operable to supply e-compass sensor data;

memory circuitry holding a tilt angle e-compass calibration parameter; and

an electronic processor coupled to said e-compass sensors and to said memory circuitry, said electronic processor responsive to the e-compass sensor data and the tilt angle e-compass calibration parameter to generate at least one signal representing a measured heading of the e-compass corrected using the tilt angle e-compass calibration parameter; and

a display coupled to said electronic processor to display information based on the corrected measured heading of the e-compass.

20. The portable electronic device claimed in claim 19 further comprising a tilt sensor coupled to supply tilt sensor data to said electronic processor.

21. The portable electronic device claimed in claim 20 wherein said electronic processor is operable to generate the at least one signal related to the ellipse tilt angle fitted to the e-compass sensor data as processed by a coarse detilting procedure on the tilt sensor data.

22. The portable electronic device claimed in claim 19 further comprising a satellite positioning decoder coupled to said electronic processor wherein said processor is operable as an electronic position engine responsive to blend signals representing information from said satellite positioning decoder and the signals representing e-compass data.

23. The portable electronic device claimed in claim 19 further comprising an accelerometer coupled to said electronic processor wherein said processor is operable as an electronic position engine responsive to signals representing information from said accelerometer and the signals representing e-compass data to supply signals representing position information.

24. The portable electronic device claimed in claim 19 wherein said electronic processor is further responsive to at least one hard iron calibration parameter to generate the at least one signal representing a measured heading of the e-compass.

25. The portable electronic device claimed in claim 19 further comprising a wireless modem coupled to said electronic processor, said electronic processor operable to display information received from said wireless modem on said display.

26. A process of manufacture comprising attaching to a printed wiring board an electronic processor and an e-compass and a flash memory holding a tilt angle e-compass calibration parameter and instructions executable by the electronic processor to generate at least one signal representing a measured heading of the e-compass corrected using the tilt angle e-compass calibration parameter.