NAVIGATION SYSTEM WITH DYNAMICALLY CALIBRATED PRESSURE SENSOR

• US 20090143983A1
• Filed: 12/04/2007
• Published: 06/04/2009
• Est. Priority Date: 12/04/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Nemerix, SA
• Inventors: VENKATRAMAN, SaiPradeep, LIU, Quanwei, GARIN, Lionel
• Granted Patent: US 8,332,137 B2
• Time in Patent Office: Days
• US Class Current: 701/214
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments
• CPC Class Codes: G01C 5/06 by using barometric means

Abstract

A navigation system includes a pressure sensor, a calibration module in communication with the pressure sensor, and an altitude module in communication with the calibration module. The calibration module is configured to determine a dynamic pressure proportionality coefficient based at least in part on a static pressure proportionality coefficient, a measured pressure value from the pressure sensor, and a velocity value. The altitude module is configured to calculate a sensor-based altitude value based at least in part on the determined dynamic pressure proportionality coefficient.

Claims

1. A navigation system comprising:

a pressure sensor;

a calibration module configured to be in communication with the pressure sensor and configured to determine dynamic pressure model information based at least in part on static pressure model information, a measured pressure value from the pressure sensor, and a velocity value; and

an altitude module in communication with the calibration module and configured to calculate a sensor-based altitude value based at least in part on the determined dynamic pressure model information.

2. The navigation system of claim 1, wherein the calibration module is further configured to determine a static pressure proportionality coefficient based at least in part on a received altitude value and a second measured pressure value from the pressure sensor.

3. The navigation system of claim 2, further comprising a global navigation satellite system chipset configured to provide a received altitude value to the calibration module.

4. The navigation system of claim 2, wherein the static pressure proportionality coefficient is determined during a static condition.

5. The navigation system of claim 1, further comprising a filtering module configured to:

receive the sensor-based altitude value from the calibration module; and

receive a global navigation satellite system (GNSS)-based altitude value from a global navigation satellite system chipset; and

combine the sensor-based altitude value and the GNSS-based altitude value to create an overall altitude value, wherein the overall altitude value is based at least in part on a noise characteristic of the GNSS-based altitude value.

6. The navigation system of claim 1, wherein the velocity value is received from at least one of a global navigation satellite system or a dead reckoning system.

7. The navigation system of claim 1, further comprising a detection module configured to identify a change in the dynamic pressure proportionality coefficient.

8. A method for calibrating a pressure sensor of a navigation system, the method comprising:

determining a static pressure value based at least in part on a first pressure measurement from the pressure sensor, wherein the first pressure measurement is taken during a static condition;

identifying a zero slope condition based on road slope information; and

determining dynamic pressure model information based at least in part on the determined static pressure, a second pressure measurement taken by the pressure sensor during a non-static condition, and a velocity value.

9. The method of claim 8, further comprising receiving the road slope information from at least one of a dead reckoning system or an attitude sensor.

10. The method of claim 8, further comprising receiving the velocity value from at least one of a global navigation satellite system chipset or a dead reckoning system.

11. The method of claim 8, further comprising using a joint estimation process to iteratively determine a calibrated dynamic pressure proportionality coefficient value based at least in part on the determined dynamic pressure model information.

12. The method of claim 11, wherein the joint estimation process comprises a least squares process.

13. The method of claim 8, wherein determining the dynamic pressure model information is further based at least in part on a static pressure proportionality coefficient.

14. A method for calibrating a pressure sensor of a navigation system, the method comprising:

determining static pressure model information based at least in part on a measured pressure value and a received altitude value; and

determining dynamic pressure model information based at least in part on the determined static pressure model information and a received velocity value.

15. The method of claim 14, wherein the dynamic pressure model information is determined based at least in part on a second measured pressure value, wherein the second measured pressure is taken during a non-static condition.

16. The method of claim 14, further comprising identifying a static condition, wherein the measured pressure value is taken during the static condition.

17. The method of claim 14, wherein determining the static pressure model information further comprises determining whether a termination condition is satisfied, wherein the termination condition is based at least in part on a plurality of determined static pressure proportionality coefficients, and further wherein the termination condition is satisfied if a difference between a first static pressure proportionality coefficient and a second static pressure proportionality coefficient does not exceed a predetermined threshold.

18. The method of claim 14, further comprising:

using the determined static pressure model information and the determined dynamic pressure model information to calculate a sensor-based altitude value;

receiving a global navigation satellite system (GNSS)-based altitude value derived from a GNSS chipset; and

combining the sensor-based altitude value and the GNSS-based altitude value to generate an overall altitude value.

19. A method for calibrating a pressure sensor of a navigation system, the method comprising:

determining static pressure model information based at least in part on a measured pressure value;

determining an expected altitude difference over a time interval; and

determining dynamic pressure model information based at least in part on the static pressure model information and the expected altitude difference.

20. The method of claim 19, wherein the expected altitude difference is based at least in part a first GNSS-based altitude value taken at a start of the time interval and a second GNSS-based altitude value taken at an end of the time interval.

21. The method of claim 19, wherein the expected altitude difference is determined based at least in part on road slope information and a horizontal distance traveled.

22. The method of claim 19, wherein determining the dynamic pressure model information comprises expressing a dynamic pressure proportionality coefficient in terms of an altitude difference using a pressure equation, and substituting the expected altitude difference into the pressure equation.

23. A method for calibrating a pressure sensor of a navigation system, the method comprising:

determining a pressure change threshold based at least in part on a first dynamic pressure proportionality coefficient corresponding to a first environmental state;

determining a change in measured pressure based at least in part on a first measured pressure value and a second measured pressure value;

determining whether the change in measured pressure exceeds the pressure change threshold; and

if the pressure change threshold is exceeded, calculating a second dynamic pressure proportionality coefficient corresponding to a second environmental state.

24. The method of claim 23, wherein the pressure change threshold is based at least in part on a velocity value and road slope information.

25. The method of claim 23, wherein the pressure change threshold is based at least in part on a first GNSS-based altitude value and a second GNSS-based altitude value.