Forward-looking altitude detector

• US 7,856,336 B2
• Filed: 06/11/2008
• Issued: 12/21/2010
• Est. Priority Date: 06/11/2008
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Van Wyck Loomis, Peter
• Primary Examiner(s): Dunn; Drew A
• Assistant Examiner(s): VO, HIEN XUAN
• Application Number:
  US12/157,519
• Publication Number:
  US 20090312975A1
• Time in Patent Office: 923 Days
• Field of Search: 702/141, 702/96, 702/150, 702/154, 342/357.06, 342/357.14, 701/216
• US Class Current: 702/141
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 5/00 Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels G01C3/20, G01C3/30 take precedence

Abstract

An altitude dead reckoning system using a measured forward speed and a measured forward-looking acceleration in a dead reckoning (DR) altitude calculator to calculate an altitude change. The DR altitude calculator may also use a measured yaw angle rate to provide compensation to improve the accuracy of the altitude change calculation.

Claims

1. A dead reckoning altimeter, comprising:

a speedometer to determine a forward speed;

an accelerometer to measure a forward acceleration;

a yaw rate sensor to measure a yaw angle rate;

a yaw compensator to determine a yaw compensation of said measured acceleration according to said yaw angle rate; and

a DR altitude calculator to use said yaw compensation, said measured acceleration and said speed to calculate an altitude change.

2. The altimeter of claim 1, wherein:

the yaw compensator includes a yaw position compensator to compensate said measured acceleration for said yaw angle rate with a linear position offset respective to a turn radius line to determine said compensated acceleration.

3. The altimeter of claim 2, further comprising:

a return-to-position compensation detector to estimate said linear position offset using a double return loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

4. The altimeter of claim 1, wherein:

the yaw compensator includes a yaw alignment compensator configured to compensate said measured acceleration for said yaw angle rate with a yaw alignment angle to determine said compensated acceleration.

5. The altimeter of claim 4, further comprising:

a return-to-position compensation detector to estimate said yaw alignment angle using a double return loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

6. A dead reckoning altimeter, comprising:

a speedometer to determine a forward speed;

an accelerometer to measure a forward acceleration;

a bias compensator to determine a bias compensation of said measured acceleration according to an accelerometer bias; and

a DR altitude calculator to use said bias compensation, said measured acceleration and said speed to calculate an altitude change.

7. The altimeter of claim 6, further comprising:

a Kalman filter configured to filter said altitude change with an external altitude fix to estimate said accelerometer bias.

8. The altimeter of claim 7, wherein:

said external altitude fix is derived from GNSS signals.

9. The altimeter of claim 7, wherein:

said external altitude fix is derived from map matching.

10. The altimeter of claim 6, further comprising:

a return-to-position compensation detector to estimate said accelerometer bias based on a return to position.

11. The altimeter of claim 6, further comprising:

a return-to-position compensation detector to estimate said accelerometer bias based on a return to position facing in an opposite direction.

12. The altimeter of claim 6, further comprising:

an incline angle calculator to calculate an incline angle based on said bias compensation, said measured acceleration and a rate of change of said speed; and

a restart bias detector to estimate said accelerometer bias at a restart of motion after a dormant time period based on a last said incline angle before said dormant time period.

13. A dead reckoning altimeter, comprising:

a speedometer to determine a forward speed;

an accelerometer to measure a forward acceleration;

a GNSS receiver to determine a GNSS-based position including a GNSS-based altitude;

a yaw rate sensor to measure a yaw angle rate; and

a DR altitude calculator to use said speed, said measured acceleration, said yaw angle rate, and said GNSS-based position for providing a DR altitude having a better accuracy than said GNSS-based altitude.

14. The altimeter of claim 13, further comprising:

a map having floors of a parking garage;

wherein;

said DR altitude is used to distinguish between said floors when said floors are not reliably distinguished by said GNSS-based altitude.

15. A method for dead reckoning altitude, comprising:

determining a forward speed;

measuring a forward acceleration with an accelerometer;

measuring a yaw angle rate with a yaw rate sensor;

in a computing device, compensating said measured acceleration according to a yaw compensation determined from said yaw angle rate; and

in a computing device, calculating an altitude change using said yaw compensation, said measured acceleration and said speed.

16. The method of claim 15, wherein:

compensating said measured acceleration includes using said yaw angle rate with a linear position offset respective to a turn radius line for determining said yaw compensation.

17. The method of claim 16, further comprising:

estimating said linear position offset using a double loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

18. The method of claim 15, wherein:

compensating said measured acceleration includes using said yaw angle rate with a yaw alignment angle for determining said yaw compensation.

19. The method of claim 18, further comprising:

estimating said yaw alignment angle using a double loop having a first return to position after one of a clockwise loop or counterclockwise loop and a second return to position after the other of said clockwise loop or counterclockwise loop.

20. A method for dead reckoning altitude, comprising:

determining a forward speed;

measuring a forward acceleration with an accelerometer;

in a computing device, compensating said measured acceleration according to an accelerometer bias to provide a bias compensation; and

in a computing device, calculating an altitude change using said bias compensation, said measured acceleration and said speed.

21. The method of claim 20, further comprising:

Kalman filtering said altitude change with an external altitude fix to estimate said accelerometer bias.

22. The method of claim 21, further comprising:

deriving said external altitude fix from GNSS signals.

23. The method of claim 21, wherein:

deriving said external altitude fix from map matching.

24. The method of claim 20, further comprising:

estimating said accelerometer bias based on a return to position.

25. The method of claim 20, further comprising:

estimating said accelerometer bias based on a return to position facing in an opposite direction.

26. The method of claim 20, further comprising:

calculating incline angle based on said bias compensation, said measured acceleration and a rate of change of said speed; and

estimating said accelerometer bias at a restart of motion after a dormant time period based on a last said incline angle before said dormant time period and said measured acceleration.

27. A method for dead reckoning altitude, comprising:

determining a forward speed;

measuring a forward acceleration with an accelerometer;

determining a GNSS-based position including a GNSS-based altitude with a GNSS receiver;

measuring a yaw angle rate with a yaw rate sensor; and

in a computing device, calculating an altitude change using said speed, said measured acceleration, said yaw angle rate, and said GNSS-based position for providing a DR altitude having a better accuracy than said GNSS-based altitude.

28. The method of claim 27, further comprising:

providing an electronic map having floors of a parking garage; and

using said DR altitude for distinguishing between said floors when said floors are not reliably distinguished by said GNSS-based altitude.