POSITION AND HEADING ERROR-CORRECTION METHOD AND APPARATUS FOR VEHICLE NAVIGATION SYSTEMS

• US 20030036847A1
• Filed: 01/08/2001
• Published: 02/20/2003
• Est. Priority Date: 01/08/2001
• Status: Active Grant

• Current Assignee: Continental Automotive Systems, Inc. (Continental AG)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Figor, Russel S., Geier, George J., Strother, Troy L.
• Granted Patent: US 6,577,952 B2
• Time in Patent Office: Days
• US Class Current: 701/209
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled

Abstract

The present invention solves the problems of the prior art by providing methods for compensating for temperature-dependent drift of bias in a vehicle heading sensor of a dead reckoning vehicle positioning system. Specifically, the invention uses a Kalman filter to generate a calibration curve for the rate of heading sensor bias drift with temperature change. The Kalman filter calculates coefficients for a model of heading sensor bias drift rate versus temperature at each point where the vehicle is stationary. The bias drift rate calibration curve is then used to estimate a heading sensor bias periodically while the vehicle is moving. The invention further provides a method for using an aging time for temperature sensor bias drift rate to force convergence of the error variance matrix of the Kalman filter. The invention further provides vehicle navigational systems that utilize the methods of the present invention.

Claims

1. A vehicle navigational system having built-in error correction comprising:

(a) a distance-traveled sensor;

(b) a heading sensor having a bias that drifts over time;

(c) a temperature sensor;

(d) a dead reckoning system having a distance traveled sensor interface, a heading sensor interface, and a temperature sensor interface, wherein the dead reckoning component receives distance-traveled data from the distance-traveled sensor, heading data from the heading sensor, and temperature data from the temperature sensor;

(e) a first computational means for determining whether the vehicle is stationary;

(f) a second computational means for estimating a calibration curve for heading sensor bias drift rate when the vehicle is stationary;

(g) a third computational means for calculating a first vehicle heading correction using an estimated bias drift rate to compensate for first vehicle heading errors induced by heading sensor bias drift; and

(h) a fourth computational means for calculating a first vehicle position correction using the first vehicle heading correction to compensate for first vehicle position errors induced by heading sensor bias drift.

2. The apparatus of claim 1 wherein the heading sensor is a gyroscope.

3. The apparatus of claim 1 wherein the heading sensor is a low-cost gyroscope.

4. The apparatus of claim 1 wherein the heading sensor is a vibrational gyroscope.

5. The apparatus of claim 1 wherein the distance-traveled sensor is an odometer.

6. The apparatus of claim 1 wherein the dead reckoning component comprises a dead reckoning processor, a heading sensor interface, a distance-traveled sensor interface and a temperature sensor interface.

7. The apparatus of claim 6 wherein the heading sensor interface is a gyroscope interface.

8. The apparatus of claim 6 wherein the distance-traveled sensor interface is an odometer interface.

9. The apparatus of claim 1 further comprising a reference vehicle position system.

10. The apparatus of claim 9 wherein the reference vehicle position system is a satellite-based positioning system.

11. The apparatus of claim 10 wherein the satellite-based positioning system is the global positioning system.

12. The apparatus of claim 11 wherein the global positioning system component comprises an antenna and a receiver.

13. The apparatus of claim 12 further comprising a global positioning system processor.

14. The apparatus of claim 9 further comprising a fifth computational means for combining the corrected vehicle heading calculated by the dead reckoning system and a vehicle heading provided by the reference vehicle position heading into an integrated vehicle heading and a sixth computational means for combining the corrected vehicle position calculated by the dead reckoning system and a vehicle position provided by the reference vehicle position heading into an integrated vehicle heading.

15. The apparatus of claim 14 wherein the fourth computational means comprises a Kalman filter.

16. The apparatus of claim 14 wherein the fifth computational means comprises a Kalman filter.

17. The apparatus of claim 1 further comprising an application specific device.

18. The apparatus of claim 17 wherein the application specific device is a unit for matching the corrected vehicle position with a map contained in the application specific device.

19. The apparatus of claim 18 further comprising a unit for displaying the map contained in the application specific device and identifying the corrected vehicle position on the displayed map.

20. The apparatus of claim 17 wherein the application specific device is a transmitter, wherein the transmitter transmits the vehicle position and heading data to a service center having a receiver.

21. A method for correcting temperature-dependent sensor drift in a vehicle navigational system comprising a distance traveled sensor, a heading sensor, a temperature sensor, and a dead reckoning component, comprising the steps of:

(a) transmitting distance-traveled data from the distance-traveled sensor to the dead reckoning component and storing the distance-traveled data in the dead reckoning component;

(b) transmitting heading data from the heading sensor to the dead reckoning component and storing the heading data in the dead reckoning component;

(c) transmitting temperature data from the temperature sensor to the dead reckoning component and storing the temperature data in the dead reckoning component;

(d) transmitting heading sensor bias data from the heading sensor to the dead reckoning component and storing the sensor bias data in the dead reckoning component;

(e) determining whether the vehicle is stationary;

(f) if the vehicle is stationary, updating an estimate for heading sensor bias drift rate using the data transmitted to and stored in the dead reckoning component; and

(g) if the vehicle is not stationary, using the last estimate of heading sensor bias drift rate to update the estimate of heading sensor bias.

22. A computer readable medium having stored therein instructions for causing a central processing unit to execute the method of claim 21.

27. The method of claim 21 wherein the method is iterated periodically.

28. The method of claim 27 wherein the method is iterated at a frequency of 1 iteration per second.

29. The method of claim 21 wherein the step of estimating a heading sensor bias drift rate comprises the steps of:

(a) taking a first measurement of heading sensor bias and a measurement of temperature when the vehicle reaches a first stationary point,

(b) taking a second measurement of heading sensor bias and a second measurement of temperature when the vehicle reaches a second stationary point;

(c) dividing the difference between the measured bias at the second stationary point and the measured bias at the second stationary point by the difference between the measured temperature at the second stationary point and the measured temperature at the second stationary point;

(d) calculating an average temperature for the two stationary points; and

(e) using a Kalman filter to estimate to coefficients of a model of the rate of bias drift in response to change in average temperature.

30. The method of claim 29 further comprising the step of using a temperature sensor bias drift rate aging time to force convergence of the error variance matrix of the Kalman filter.

31. The method of claim 30 wherein the aging time is updated at each vehicle stationary point.

23. A method for correcting heading and position error induced by temperature-dependent heading sensor drift in a vehicle navigational system comprising a distance traveled sensor, a heading sensor, a temperature sensor, and a dead reckoning component, comprising the steps of:

(a) transmitting distance-traveled data from the distance-traveled sensor to the dead reckoning component and storing the distance-traveled data in the dead reckoning component;

(b) transmitting heading data from the heading sensor to the dead reckoning component and storing the heading data in the dead reckoning component;

(c) transmitting temperature data from the temperature sensor to the dead reckoning component and storing the temperature data in the dead reckoning component;

(d) transmitting heading sensor bias data from the heading sensor to the dead reckoning component and storing the sensor bias data in the dead reckoning component;

(e) determining whether the vehicle is stationary;

(f) if the vehicle is stationary, updating an estimate for heading sensor bias drift rate using the data transmitted to and stored in the dead reckoning component; and

(g) if the vehicle is not stationary, using the last estimate of heading sensor bias drift rate to update the estimate of heading sensor bias;

(h) estimating a vehicle heading using the heading data transmitted to and stored in the dead reckoning component and the estimated heading sensor bias;

(i) estimating a vehicle position using the distance-traveled data transmitted to and stored in the dead reckoning component, the estimated vehicle heading, and the estimated heading sensor bias.

24. A computer readable medium having stored therein instructions for causing a central processing unit to execute the method of claim 23.

25. A method for correcting heading and position error induced by temperature-dependent heading sensor drift in a vehicle navigational system comprising a distance traveled sensor, a heading sensor, a temperature sensor, and a dead reckoning component, comprising the steps of:

(a) transmitting distance-traveled data from the distance-traveled sensor to the dead reckoning component and storing the distance-traveled data in the dead reckoning component;

(b) transmitting heading data from the heading sensor to the dead reckoning component and storing the heading data in the dead reckoning component;

(c) transmitting temperature data from the temperature sensor to the dead reckoning component and storing the temperature data in the dead reckoning component;

(d) transmitting heading sensor bias data from the heading sensor to the dead reckoning component and storing the sensor bias data in the dead reckoning component;

(e) determining whether the vehicle is stationary;

(f) if the vehicle is stationary, updating an estimate for heading sensor bias drift rate using the data transmitted to and stored in the dead reckoning component; and

(g) if the vehicle is not stationary, using the last estimate of heading sensor bias drift rate to update the estimate of heading sensor bias;

(h) estimating a vehicle heading using the heading data transmitted to and stored in the dead reckoning component and the estimated heading sensor bias;

(i) estimating a vehicle position using the distance-traveled data transmitted to and stored in the dead reckoning component, the estimated vehicle heading, and the estimated heading sensor bias;

(j) calculating an integrated vehicle heading using the estimated vehicle heading and the global positioning data transmitted to the global positioning system component; and

(k) calculating an integrated vehicle position using the estimated vehicle position and the global positioning data transmitted to the global positioning system component.

26. A computer readable medium having stored therein instructions for causing a central processing unit to execute the method of claim 25.