Low power position locator

• US 20030236619A1
• Filed: 02/20/2003
• Published: 12/25/2003
• Est. Priority Date: 06/25/2002
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Dorian, A. Challoner, Wiberg, Dean V.
• Granted Patent: US 6,859,725 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 5/019 Energy consumption

Abstract

Embodiments of the invention generally encompass a device for determining a user position including an RF position locating device (e.g., a GPS receiver) for intermittently determining a reference position and an inertial sensing system for determining a position change from the reference position. A current position is determined from the reference position and the position change and the inertial sensing system operates at a lower power level than the RF position locating device.

Claims

1. A device comprising:

a radio frequency (RF) position locating device for intermittently determining a reference position; and

an inertial sensing system for determining a position change relative to the reference position;

wherein a current position is determined from the reference position and the position change and the inertial sensing system operates at a lower power level than the RF position locating device.

2. The device of claim 1, wherein the reference position is determined using an apriori estimate from the inertial sensing system.

3. The device of claim 1, wherein the RF position locating device comprises a global positioning system (GPS) receiver for intermittently determining the reference position.

4. The device of claim 1, wherein a first power of the inertial sensing system is less than a second power of the RF position locating device multiplied by an inverse of a duty cycle of the RF position locating device.

5. The device of claim 1, wherein RF position locating device is used to determine the reference position only if the position change determined by the inertial sensing system exceeds a specified limit.

6. The device of claim 1, wherein RF position locating device is used to determine the reference position at substantially regular time intervals.

7. The device of claim 1, wherein the inertial sensing system includes at least one microelectromechanical system (MEMS) sensor.

8. The device of claim 7, wherein the inertial sensing system includes three MEMS accelerometers for determining a translation vector and three MEMS gyros for determining an orientation change wherein the position change comprises a combination of the translation vector and the orientation change.

9. The device of claim 7, wherein the inertial sensing system includes three MEMS sensors each sensing a measurement for one of three mutually orthogonal axes.

10. A method comprising the steps of:

intermittently determining a reference position with a radio frequency (RF) position locating device; and

determining a position change relative to the reference position with an inertial sensing system;

wherein a current position is determined from the reference position and the position change and the inertial sensing system operates at a lower power level than the RF position locating device.

11. The method of claim 10, wherein the reference position is determined using an apriori estimate from the inertial sensing system.

12. The method of claim 10, wherein the RF position locating device comprises a global positioning system (GPS) receiver for intermittently determining the reference position.

13. The method of claim 10, wherein a first power of the inertial sensing system is less than a second power of the RF position locating device multiplied by an inverse of a duty cycle of the RF position locating device.

14. The method of claim 10, wherein RF position locating device is used to determine the reference position only if the position change determined by the inertial sensing system exceeds a specified limit.

15. The method of claim 10, wherein RF position locating device is used to determine the reference position at substantially regular time intervals.

16. The method of claim 10, wherein the inertial sensing system includes at least one microelectromechanical system (MEMS) sensor.

17. The method of claim 16, wherein the inertial sensing system includes three MEMS accelerometers for determining a translation distance and three MEMS gyros for determining an orientation change wherein the position change comprises a combination of the translation distance and the orientation change.

18. The method of claim 16, wherein the inertial sensing system includes three MEMS sensors each sensing a measurement for one of three mutually orthogonal axes.