Method and apparatus for improving dead reckoning distance calculation in vehicle navigation system

• US 6,360,165 B1
• Filed: 10/21/1999
• Issued: 03/19/2002
• Est. Priority Date: 10/21/1999
• Status: Expired due to Term

• Current Assignee: TomTom Navigation B.V (TomTom NV)
• Original Assignee: Visteon Technologies LLC (Visteon Corporation)
• Inventors: Chowdhary, Mahesh
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US09/422,830
• Time in Patent Office: 880 Days
• Field of Search: 701/200, 701/201, 701/205, 701/206, 701/207, 701/213, 702/85, 702/97, 731/78.R, 337/00, 337/72
• US Class Current: 701/205
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments
• CPC Class Codes: G01C 22/02 by conversion into electric waveforms and subsequent integration, e.g. using tachometer generator G01C22/002, G01C22/004, G01C22/006 take precedence

Abstract

The present invention enables a vehicle navigation system to automatically compensate for odometer measurement errors due to changes in tire size and/or slip, and to avoid odometer recalibration when slip is present. These capabilities improve the accuracy and reliability of the vehicle navigation system. Slip of a vehicle, e.g., a loss of traction, can occur when a road is wet or covered with snow or ice. It can occur when a road is dry, and a vehicle is accelerating or decelerating rapidly. It can occur rounding a sharp corner. Because an odometer is typically hooked up to a driven wheel, the engine or transmission, there may be large sources of error in the distance estimates derived from the odometer. Utilizing conveniently derived slip signals from an anti-lock brake system (ABS) or from a traction control system (TCS), the slip of the vehicle can be accounted for, even absent a GPS signal to recalibrate the system. This allows for improved accuracy of the system which is particularly noticeable in urban environments where GPS signals may not be available.

Claims

1. A method for navigating a vehicle comprising the acts of:

obtaining during a first time interval an odometer indication signal indicative of a distance traveled by the vehicle, a slip indication signal indicative of the slip of the vehicle, and a heading indication signal indicative of the heading of the vehicle;

converting the odometer indication signal to a first distance estimate;

determining a position of the vehicle based on a known prior position, the first distance estimate obtained during said act of converting and the heading of the vehicle indications of which are obtained during said first act of obtaining;

obtaining during the first time interval an external distance estimate for the vehicle from a radio navigation system;

determining whether the external distance estimate includes indicia of reliability; and

adjusting an odometer conversion parameter utilized in said act of converting if the external distance estimate includes indicia of reliability as determined in said second act of determining.

2. The method for navigating a vehicle of claim 1, further comprising the acts of:

correcting an error in the position of the vehicle determined in said first act of determining if the external distance estimate includes indicia of reliability as determined in said second act of determining.

3. The method for navigating a vehicle of claim 1, further comprising the acts of:

calculating a difference between the adjusted first distance estimate and the external distance estimate; and

correcting an error in the position of the vehicle determined in said first act of determining if the external distance estimate includes indicia of reliability as determined in said second act of determining and the difference as determined in said act of calculating exceeds a first threshold value.

4. The method for navigating a vehicle of claim 1, wherein the converting act further comprises the act of:

correcting the first distance estimate using data derived from the slip indication signal.

5. The method for navigating a vehicle of claim 4, wherein the adjusting act further comprises:

adjusting an odometer conversion parameter utilized in said act of converting if the external distance estimate includes indicia of reliability as determined in said second act of determining and values representative of the slip indication signal obtained in said first act of obtaining fall below a second threshold value.

6. The method for navigating a vehicle of claim 5, wherein the odometer conversion parameter includes a constant proportionate to a ratio of a distance traveled to the number of rotations indicated by the odometer indication signal.

7. The method for navigating a vehicle of claim 6, wherein the converting act further comprises the act of:

multiplying a value representative of the odometer signal by the constant to form the first distance estimate.

8. The method for navigating a vehicle of claim 1, wherein the radio navigation system includes a global positioning satellite sensor which generates the external distance estimate for the vehicle.

9. The method of claim 1, wherein the first and second obtaining and determining acts, the converting and adjusting acts, are repeated a plurality of times during successive time intervals to track a movement of the vehicle.

10. The method of claim 1, further comprising the act of:

determining a slip difference between a left and a right wheel of the vehicle; and

correcting the heading indication signal for the vehicle based on the slip difference calculated in said determining act.

11. A vehicle navigation system comprising:

an odometer generating an odometer indication signal indicative of a distance traveled by the vehicle;

a slip sensor generating a slip indication signal indicative of a slip of the vehicle;

a heading sensor generating a heading indication signal indicative of the heading of the vehicle;

a first logic for converting the odometer indication signal to a first distance estimate utilizing an odometer conversion parameter and for determining a position of the vehicle based on a known prior position, the first distance estimate and the heading of the vehicle indications of which are obtained from said heading sensor;

a radio navigation sensor for receiving radio navigation signals; and

a second logic for converting the radio navigation signals to an external distance estimate for the vehicle, for determining whether the external distance estimate includes indicia of reliability; and

for adjusting the odometer conversion parameter utilized by said first logic if the external distance estimate includes indicia of reliability.

12. The vehicle navigation system recited in claim 11, wherein the first logic uses data from the slip indication signal to convert the odometer indication signal to a first distance estimate.