Method and system for determining the location of a vehicle

• US 20060220954A1
• Filed: 03/31/2005
• Published: 10/05/2006
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Hunt, Kenneth Edward, Zeitzew, Michael Alan, Schmidt, Mark Alvin, Holm, David Roy, Stephens, Scott Adam
• Granted Patent: US 7,479,922 B2
• Time in Patent Office: Days
• US Class Current: 342/357.310
• CPC Class Codes: G01S 1/06 Means for providing multiple indication, e.g. coarse and fine indications
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system

Abstract

A first location determining receiver determines a first location estimate of a vehicle. The first location determining receiver is associated with satellite beacons. A second location determining receiver determines a second location estimate of a vehicle. The second location determining receiver is exclusively associated with terrestrial beacons. A selector selects the first location estimate of the vehicle as a preferential location in accordance with an initialization scheme for the vehicle in a work area. A filtering module applies a first weight to a first location and a second weight to the second location to derive a weighted estimate as the preferential location upon satisfactory completion of the initialization scheme.

Claims

1. A method for accurately determining a location of a vehicle, the method comprising:

determining a first location estimate of a vehicle based on a first location determining receiver associated with satellite beacons;

determining a second location estimate of a vehicle based on a second location determining receiver exclusively associated with terrestrial beacons;

selecting the first location estimate of the vehicle as a preferential location in accordance with an initialization scheme for the vehicle in a work area; and

applying a first weight to a first location and a second weight to the second location to derive a weighted estimate as the preferential location upon satisfactory completion of the initialization scheme.

2. The method according to claim 1 further comprising:

establishing the first weight based on a first variance of the first location estimate such that the first weight varies generally inversely to the first variance; and

establishing the second weight based on a second variance of the second location estimate such that the second weight varies generally inversely with the second variance.

3. The method according to claim 1 further comprising:

establishing a first target probability density function for the first location estimate based on empirical measurements in a work area;

establishing a second target probability density function for the second location estimate based on empirical measurements in the work area; and

providing a soft transition from a first location estimate as the dominant estimate and a second location estimate as the dominant estimate by limiting a rate of change in the first weight and the second weight in accordance with the first target probability density function and the second probability density function.

4. The method according to claim 1 wherein the initialization scheme comprises a time period between start-up of a vehicle and moving the vehicle into a defined home position in a work area for execution of a task in the work area.

5. The method according to claim 1 wherein the initialization scheme comprises a time period between start-up of a vehicle and moving the vehicle into a defined home position in a work area for execution of a path plan in the work area.

6. The method according to claim 1 wherein the initialization scheme comprises a time period between start-up of a vehicle and verification that the second location determining receiver receives at least one of a pilot signal and an initialization transmission associated with the stationary beacons around the work area.

7. The method according to claim 1 wherein the applying of the first weight and the second weight conforms to a least squares estimation for the first location estimate and the second location estimate.

9. The method according to claim 1 wherein the applying of the first weight and the second weight conforms to a weighted least squares estimation for the first location estimate and the second location estimate.

10. The method according to claim 9 wherein the weighted least squares estimation is consistent with a generally linear relationship of the first location estimate and the second location estimate over time.

11. The method according to claim 1 further comprising:

providing measurement predictions and variances associated with the first location estimate and the second location estimate; and

limiting a tracking loop of location measurement data based on feedback of the measurement predictions and variances.

8. The method according to claim 8 wherein the least squares estimation is consistent with a generally linear relationship of the first location estimate and the second location estimate over time.

12. A method for accurately determining a location of a vehicle, the method comprising:

determining a first location estimate of a vehicle based on a first location determining receiver associated with satellite beacons;

determining a second location estimate of a vehicle based on a second location determining receiver exclusively associated with terrestrial beacons;

applying a first weight to a first location and a second weight to the second location to derive a weighted estimate as a preferential location of the vehicle;

establishing a first target probability density function for the first location estimate based on empirical measurements in a work area;

establishing a second target probability density function for the second location estimate based on empirical measurements in the work area; and

providing a soft transition from the first location estimate as a dominant estimate in the weighted estimate and the second location estimate as the dominant estimate in the weighted estimate by limiting a rate of change in the first weight and the second weight in accordance with the first target probability density function and the second probability density function.

13. The method according to claim 12 further comprising:

establishing the first weight based on a first variance of the first location estimate such that the first weight varies inversely to the first variance; and

establishing the second weight based on a second variance of the second location estimate such that the second weight varies inversely with the second variance.

14. A system for accurately determining a location of a vehicle, the system comprising:

a first location determining receiver for determining a first location estimate of a vehicle based on a first location determining receiver associated with satellite beacons;

a second location determining receiver for determining a second location estimate of a vehicle based on a second location determining receiver exclusively associated with terrestrial beacons;

a selector for selecting the first location estimate of the vehicle as a preferential location in accordance with an initialization scheme for the vehicle in a work area; and

a filtering module for applying a first weight to a first location and a second weight to the second location to derive a weighted estimate as the preferential location upon satisfactory completion of the initialization scheme.

15. The system according to claim 14 further comprising:

a variance monitor for establishing the first weight based on a first variance of the first location estimate and for establishing a second weight based on a second variance of the second location estimate such that the first weight varies inversely to the first variance and such that the second weight varies inversely with the second variance.

16. The system according to claim 14 further comprising:

a definer for establishing a first target probability density function for the first location estimate based on empirical measurements in a work area and for establishing a second target probability density function for the second location estimate based on empirical measurements in the work area; and

a transition manager for providing a soft transition from a first location estimate as the dominant estimate and a second location estimate as the dominant estimate by limiting a rate of change in the first weight and the second weight in accordance with the first target probability density function and the second probability density function.

17. The system according to claim 14 wherein the initialization scheme comprises a time period between start-up of a vehicle and moving the vehicle into a defined home position in a work area for execution of a task in the work area.

18. The system according to claim 14 wherein the initialization scheme comprises a time period between start-up of a vehicle and moving the vehicle into a defined home position in a work area for execution of a path plan in the work area.

19. The system according to claim 14 wherein the initialization scheme comprises a time period between start-up of a vehicle and verification that the second location determining receiver receives at least one of a pilot signal and an initialization transmission associated with the stationary beacons around the work area.

20. The system according to claim 14 wherein the filtering module is arranged to apply the first weight and the second weight to conform to a least squares estimation for the first location estimate and the second location estimate.

21. The system according to claim 20 wherein the least squares estimation is consistent with a generally linear relationship of the first location estimate and the second location estimate over time.

22. The system according to claim 14 further comprising:

a focused acquisition manager associated with at least one of the first location determining receiver and the second location determining receiver for limiting a tracking loop of location measurement data;

a feedback manager for providing measurement predictions and variances from the filtering module to the focused acquisition manager.

23. A system for accurately determining a location of a vehicle, the system comprising:

a first location determining receiver for determining a first location estimate of a vehicle based on a first location determining receiver associated with satellite beacons;

a second location determining receiver for determining a second location estimate of a vehicle based on a second location determining receiver exclusively associated with terrestrial beacons;

a filtering module for applying a first weight to a first location and a second weight to the second location to derive a weighted estimate as a preferential location of the vehicle;

a definer for establishing a first target probability density function for the first location estimate based on empirical measurements in a work area and for establishing a second target probability density function for the second location estimate based on empirical measurements in the work area; and

a transition manager for providing a soft transition from the first location estimate as a dominant estimate in the weighted estimate and the second location estimate as the dominant estimate in the weighted estimate by limiting a rate of change in the first weight and the second weight in accordance with the first target probability density function and the second probability density function.

24. The system according to claim 23 wherein the filtering module establishes the first weight based on a first variance of the first location estimate such that the first weight varies inversely to the first variance;

the filtering module establishing the second weight based on a second variance of the second location estimate such that the second weight varies inversely with the second variance.