Accurate magnetic compass in mobile electronic device

• US 8,880,373 B2
• Filed: 11/04/2009
• Issued: 11/04/2014
• Est. Priority Date: 11/04/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kulik, Victor, Brunner, Christopher
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): Zhang, Haidong
• Application Number:
  US12/612,529
• Publication Number:
  US 20110106474A1
• Time in Patent Office: 1,826 Days
• Field of Search: 702/92
• US Class Current: 702/92
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

Methods and apparatus are described herein for calibration and correction of non-constant sensor errors, and in particular non-constant compass errors, that are based in part on changing software and hardware modes of a host device. The non-constant errors induced in the sensor by each mode and combination of modes is determined in a calibration that may be determined during pre-production testing of one or more host devices. The calibration results can be incorporated into software and/or hardware of the host device. During normal operation, a sensor correction can be applied to sensor measurements based in part on the active mode or combination of modes.

Claims

1. A method of dynamic sensor correction, the method comprising:

determining a sensor output value;

determining a dynamic state of a host device having the sensor;

determining that a change in the dynamic state of the host device by an electric current generated by the host device distorts the sensor output value such that the sensor output value has reduced accuracy;

determining the existence of a user calibration value;

determining a calibration value based on the sensor, the change in the dynamic state, and if said user calibration value exists, the user calibration value; and

applying the calibration value to the sensor output value to generate a corrected sensor output value that is more accurate than the distorted sensor output value.

2. The method of claim 1, wherein determining the sensor output value comprises determining an output value from an electronic magnetic compass.

3. The method of claim 1, wherein determining the sensor output value comprises retrieving a sensor output value from a storage register.

4. The method of claim 1, wherein the host device is a mobile device having a Global Navigation Satellite System (GNSS) receiver, and determining the dynamic state comprises determining a dynamic state of the mobile device.

5. The method of claim 1, wherein determining the dynamic state comprises determining a hardware state.

6. The method of claim 1, wherein determining the dynamic state comprises determining presence of a transitory state.

7. The method of claim 1, wherein determining the dynamic state comprises determining a wireless communication transceiver state.

8. The method of claim 1, wherein determining the dynamic state comprises determining a Global Navigation Satellite System (GNSS) receiver state.

9. The method of claim 1, wherein determining the dynamic state comprises determining an amplifier state.

10. The method of claim 9, wherein the amplifier state comprises an amplifier gain state.

11. The method of claim 1, wherein determining the dynamic state comprises determining a display backlight state.

12. The method of claim 1, wherein determining the dynamic state comprises determining a battery charging state.

13. The method of claim 1, wherein the host device is a mobile device, and determining the dynamic state comprises determining a combination of states within the mobile device.

14. The method of claim 1, wherein the host device is a mobile device, and determining the dynamic state comprises:

monitoring each of a plurality of states within the mobile device; and

updating a state table based on the monitoring.

15. The method of claim 1, wherein determining the calibration value comprises retrieving the calibration value corresponding to the dynamic state from a calibration table.

16. The method of claim 15, wherein determining the calibration value further comprises:

determining a presence of at least one transitory state in the dynamic state; and

maintaining a prior calibration value.

17. The method of claim 15, wherein determining the calibration value further comprises selecting from multiple calibration values corresponding to the dynamic state reported by a state monitor.

18. The method of claim 1, wherein applying the calibration value to the sensor output value comprises summing the calibration value with the sensor output value.

19. The method of claim 1, wherein applying the calibration value to the sensor output value comprises summing a prior calibration value to a prior sensor output value.

20. The method of claim 1, further comprising determining the existence of an automatic calibration value.

21. The method of claim 20, wherein said determining the calibration value is based further on:

if it exists, the automatic calibration value.

22. A dynamic sensor correction apparatus, the apparatus comprising:

a state monitor configured to determine a dynamic state of a host device; and

a correction module, said correction module being coupled to the state monitor and configured to determine a sensor output value, determine that a change in the dynamic state of the host device by an electric current generated by the host device distorts the sensor output value such that the sensor output value has reduced accuracy;

determine a calibration based on the state of the host device, and output a corrected sensor output value based at least in part on a user initiated calibration and the state of the host device, wherein the corrected sensor output value is more accurate than the distorted sensor output value.

23. The apparatus of claim 22, wherein the host device is a mobile device, and the state monitor is configured to further determine a dynamic hardware state within the mobile device.

24. The apparatus of claim 22, the host device is a mobile device, and wherein the state monitor is configured to monitor each of a plurality of states within the mobile device and update a state table based on the monitoring.

25. The apparatus of claim 22, further comprising:

a calibration table, and

wherein the correction module is configured to determine the dynamic state from the state monitor and retrieve a calibration value from the calibration table based on the dynamic state.

26. The apparatus of claim 25, wherein the calibration table maps each of a plurality of possible dynamic states to a corresponding calibration value.

27. The apparatus of claim 22, wherein the correction module is configured to determine a presence of a transitory state from the state monitor, and selectively freeze the corrected sensor output value in the presence of the transitory state.

28. The apparatus of claim 22, wherein the correction module comprises:

a first register configured to receive and store the sensor output value; and

a summer having a first input coupled to the first register and a second input configured to receive a calibration value, and wherein an output of the summer provides the corrected sensor output value.

29. The apparatus of claim 22, wherein the correction module further determines the calibration based at least in part on an automatic calibration.

30. The apparatus of claim 22, wherein the correction module is further configured to output the corrected sensor output value based further on correction values supplied by the user initiated calibration.

31. The apparatus of claim 29, wherein the correction module is further configured to output the corrected sensor output value based further on correction values supplied by the automatic calibration.

32. A dynamic sensor correction apparatus, the apparatus comprising:

means for determining a sensor output value;

means for determining a dynamic state of a host device having the sensor;

means for determining that a change in the dynamic state of the host device by an electric current generated by the host device distorts the sensor output value such that the sensor output value has reduced accuracy;

means for identifying the existence of a user calibration value;

means for determining a calibration value based on the sensor, the change in the dynamic state, and, if said user calibration value exists, the user calibration value, and

means for applying the calibration value to the sensor output value to generate a corrected sensor output value that is more accurate than the distorted sensor output value.

33. The apparatus of claim 32, wherein the means for determining the dynamic state is configured to determine at least one of a hardware state, a wireless communication transceiver state, a Global Navigation Satellite System (GNSS) receiver state, a display backlight state, an Automatic Gain Control (AGC) state, or a battery charging state.

34. The apparatus of claim 32, wherein the host device is a mobile device, and the means for determining the dynamic state comprises:

means for monitoring each of a plurality of states within the mobile device; and

means for updating a state table based on the monitoring.

35. The apparatus of claim 32, wherein the means for determining the calibration value further comprises:

means for determining a presence of at least one transitory state in the dynamic state; and

means for maintaining a prior calibration value.

36. The apparatus of claim 32, further comprising

means for identifying the existence of an automatic calibration value;

and

said means for determining the calibration value based further on;

if it exists, the automatic calibration value.

37. A non-transitory storage media having one or more processor readable instruction encoded thereon, when executed by the processor performing dynamic sensor correction, the instructions comprising:

instructions for determining a sensor output value;

instructions for determining a dynamic state of a host device having the sensor;

instructions for determining that a change in the dynamic state of the host device by an electric current generated by the host device distorts the sensor output value such that the sensor output value has reduced accuracy;

instructions for determining the existence of a user calibration value;

instructions for determining a calibration value based on the sensor, the change in the dynamic state, and, if said user calibration value exists, the user calibration value; and

instructions for applying the calibration value to the sensor output value to generate a corrected sensor output value.

38. The non-transitory storage media of claim 37, wherein the instructions encoded on the storage media for determining the dynamic state comprise at least one of:

instructions for determining a hardware state,

instructions for determining a wireless communication transceiver state,

instructions for determining a Global Navigation Satellite System (GNSS) receiver state,

instructions for determining a display backlight state, an Automatic Gain Control (AGC) state, or

instructions for determining a battery charging state.

39. The storage media of claim 37, further comprising

instructions for determining the existence of an automatic calibration value;

and

said instructions for determining a calibration value based further on;

if it exists, the automatic calibration value.