Vehicle heading change determination using compensated differential wheel speed

• US 6,631,321 B1
• Filed: 10/29/2001
• Issued: 10/07/2003
• Est. Priority Date: 10/29/2001
• Status: Expired due to Term

• Current Assignee: HERE Global B.V. (Nokia Corporation)
• Original Assignee: Navigation Technologies Corp. (Nokia Corporation)
• Inventors: Ciprian, Joseph
• Primary Examiner(s): Marc-Coleman, Marthe Y.
• Application Number:
  US10/055,497
• Time in Patent Office: 708 Days
• Field of Search: 701/207, 701/208, 701/215, 701/216, 701/217, 701/224, 701/72, 701/75, 340/988, 340/990, 340/995, 342/451, 342/357.14, 342/357.13
• US Class Current: 701/207
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments

Abstract

A vehicle positioning application in a navigation system provides for determining a change of vehicle heading using differential wheel speed sensors and compensates for dynamic and static changes in the wheel radii.

Claims

1. A method of compensating for differential wheel speed (DWS) heading determination errors in a navigation system for a vehicle, comprising:

a) calculating a heading change value according to a DWS formula of;

(dL−

dR)/dWT;

where;

dL is distance traveled as derived from a left wheel sensor,

dR is distance traveled as derived from a right wheel sensor, and

dWT is the wheel track distance between the left wheel and the right wheel; and

b) compensating for wheel radii change induced error in the heading change value according to the DWS formula by factoring in lateral acceleration, distance through a turn, and a vehicle constant for the course of the vehicle during the heading change.

2. The method according to claim 1 further comprising:

deriving the vehicle constant by the formula;

3. The method according to claim 2 further comprising:

recalculating the vehicle constant after each detected turn.

4. The method according to claim 3 further comprising:

updating the vehicle constant at each detected turn by the formula;

5. The method according to claim 4 further comprising:

deriving an estimated lateral acceleration by multiplying yaw rate times speed through the turn.

6. The method according to claim 5 wherein the yaw rate is determined by the heading change and vehicle speed as derived from wheel speed sensor data.

7. The method according to claim 1 further comprising:

detecting that the vehicle has made a turn to trigger the compensating for wheel radii change induced error in the heading change value.

8. A method of compensating for differential wheel speed heading determination errors in a vehicle navigation system, comprising:

a) instituting a long term, low weighted correction algorithm for a first heading change value; and

b) correcting the long term, low weighted correction algorithm with a short term, high weighted correction value derived from an inter-wheel differential radius measurement sample between a left wheel and right wheel opposing wheel pair;

wherein said short term, high weighted correction value is derived according to the formula;

dr=rL−

rR;

where;

dr is the inter-wheel radius differential value, rL is the left wheel radius and rR is the right wheel radius, and

calculating an updated, or new, inter-wheel radius differential value, drnew, according to;

drnew=Average (dr);

where;

the average is based on a number of samples,

and further adjusting each of the left and right radii by a selected weight whereby,

rLnew=rL−

(dr(new)−

dr(old))/selected weight, and

rRnew=rR+(dr(new)−

dr(old))/selected weight.

9. The method according to claim 8 further comprising:

deriving the first heading change value from a GPS sensor.

10. The method according to claim 8 further comprising:

deriving the inter-wheel radius differential from a speed pulse sensor on each of the left wheel and right wheel of the opposing wheel pair.

11. The method according to claim 8 wherein the selected weight is four.

12. The method according to claim 8 further comprising:

using the drnew value only if the variance among the measurement samples is within a predetermined range and no outliers are detected, thereby indicating that the drnew value is valid.

13. The method according to claim 12 further comprising adjusting the inter-wheel radius value only if (drew−

drold)/drold)>

0.025%).

14. The method according to claim 8 further comprising adjusting the inter-wheel radius value only if (drew−

drold)/drold)>

0.025%).

15. The method according to claim 8 further comprising adjusting the inter-wheel radius value only if (drew−

drold)/drold) exceeds a preselected percent value.