ACCURATE MAGNETIC COMPASS IN MOBILE ELECTRONIC DEVICE

• US 20110106474A1
• Filed: 11/04/2009
• Published: 05/05/2011
• Est. Priority Date: 11/04/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kulik, Victor, Brunner, Christopher
• Granted Patent: US 8,880,373 B2
• Time in Patent Office: Days
• 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 a calibration value based on the sensor and the dynamic state; and

applying the calibration value to the sensor output value to generate a corrected 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 determining the dynamic state comprises determining the dynamic state of a mobile device having a Global Navigation Satellite System (GNSS) receiver.

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 a software state.

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

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

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

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

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

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

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

14. The method of claim 1, wherein determining the dynamic state comprises determining a combination of states within a mobile device.

15. The method of claim 1, wherein determining the dynamic state comprises:

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

updating a state table based on the monitoring.

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

17. The method of claim 16, 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.

18. The method of claim 16, wherein determining the calibration value further comprises selecting from multiple calibration values corresponding to the dynamic state reported by a state monitor.

19. 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.

20. 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.

21. 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 coupled to the state monitor and configured to determine a sensor output value, determine a calibration based on the state of the host device, and output a corrected sensor output value based at least in part on the calibration and the state of the host device.

22. The apparatus of claim 21, wherein the state monitor is configured to determine at least one of a dynamic hardware state or a dynamic software state within a mobile device.

23. The apparatus of claim 21, wherein the state monitor is configured to monitor each of a plurality of states within a mobile device and update a state table based on the monitoring.

24. The apparatus of claim 21, 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.

25. The apparatus of claim 24, wherein the calibration table maps each of a plurality of possible dynamic states to a corresponding calibration value.

26. The apparatus of claim 21, 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.

27. The apparatus of claim 21, 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.

28. 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 a calibration value based on the sensor and the dynamic state; and

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

29. The apparatus of claim 28, wherein the means for determining the dynamic state is configured to determine at least one of a hardware state, a software 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.

30. The apparatus of claim 28, wherein the means for determining the dynamic state comprises:

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

means for updating a state table based on the monitoring.

31. The apparatus of claim 28, 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.

32. A 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 a calibration value based on the sensor and the dynamic state; and

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

33. The storage media of claim 32, 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 software 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.