Vehicle navigation system and method using multiple axes accelerometer

• US 6,308,134 B1
• Filed: 11/30/1998
• Issued: 10/23/2001
• Est. Priority Date: 12/28/1995
• Status: Expired due to Term

• Current Assignee: MiTAC International Corporation (MiTAC Holdings Corp.)
• Original Assignee: Magellan DIS, Inc.
• Inventors: Croyle, Steven R., Sittaro, Ernie R., Spencer, II, Larry E.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): To, Tuan C
• Application Number:
  US09/091,430
• Time in Patent Office: 1,058 Days
• Field of Search: 701/220, 701/207, 701/1, 364/454, 235/150.27
• US Class Current: 701/220
• CPC Class Codes: G01C 21/16 by integrating acceleration or speed, i.e. inertial navigation
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network

Abstract

The improved vehicle navigation system uses a multiple, orthogonal axes accelerometer, such as two or three accelerometers which are mounted orthogonal to one another. The two axes whose acceleration are to be measured are the longitudinal (nose to rear bumper) axis and lateral (left to right side) axis. The tangential or longitudinal axis acceleration is integrated once to obtain longitudinal speed and is integrated again to produce a vehicle displacement. The lateral accelerometer measures the centripetal force that the vehicle is encountering which is used to compute a centripetal or lateral acceleration. The lateral acceleration is used to obtain a heading change derived from the lateral acceleration information and the longitudinal speed. Using the heading change and the longitudinal acceleration, the improved vehicle navigation system propagates a previous position to a current position. This is accomplished without the need for connection to the vehicle speed sensor and the heading sensor. If a third axis acceleration measurement sensor is used the improved vehicle navigation system can operate completely independent of vehicle sensors, further increasing flexibility in mounting. The third accelerometer provides pitch to assist in calibrating the other accelerometers or other sensors and in altering the longitudinal and/or lateral acceleration information by, for example, detecting a banked turn.

Claims

1. A vehicle navigation system (10) comprising:

an orthogonal axes accelerometer (20) provides longitudinal acceleration information and lateral acceleration information; and

said vehicle navigation system (10) derives longitudinal speed from said longitudinal acceleration information and derives heading change from said lateral acceleration information and said longitu dinal speed and uses said heading change and said longitudinal acceleration information to propagate a previous position to a current position.

2. The system of claim 1 wherein said vehicle navigation system (10) assigns an axis of said orthogonal axes accelerometer to a particular axis by comparing the difference between a first acceleration information and second acceleration information to a predetermined threshold and by comparing said first and second acceleration information to acceleration measurements derived from at least one other sensor in said particular axis, and said system assigns said particular axis to said axis of said accelerometer having acceleration information closest to said acceleration information derived from at least one other sensor.

3. The system of claim 1 wherein said vehicle navigation system (10) determines lateral and longitudinal calibration accelerations from GPS velocities, said system calibrates said lateral and longitudinal acceleration information with said latitudinal and longitudinal calibration accelerations.

4. The system of claims 3 wherein said system updates scale factors for said lateral and longitudinal acceleration information using said latitudinal and longitudinal calibration accelerations.

5. The vehicle navigation system (10) of claim 2 wherein said vehicle navigation system compares the difference between said first acceleration information and said second acceleration information to a predetermined threshold to ensure the accelerations are different enough for valid axis assignment.

6. The vehicle navigation system (10) of claim 1 wherein said orthogonal axes accelerometer further provides vertical acceleration information and said vehicle navigation system uses said vertical acceleration information to calibrate said longitudinal and lateral acceleration information.

7. A method of propagating a previous position to a current position in a vehicle navigation system (10), said method including the steps of:

providing longitudinal acceleration information;

providing lateral acceleration information;

deriving longitudinal speed from said longitudinal acceleration information;

deriving heading change from said lateral acceleration information and said longitudinal speed; and

using said heading change and said longitudinal acceleration to propagate a previous position to a current position.

8. The method of claim 7 further including the steps of:

providing vertical acceleration information; and

using said vertical information to calibrate said longitudinal and lateral acceleration information.

9. The method of claim 7 further including, for orienting acceleration information to a particular axis, the steps of:

comparing the difference between first acceleration information and second acceleration information to a predetermined threshold;

comparing said first and second acceleration information to acceleration measurements derived from at least one other sensor in said particular axis; and

assigning said particular axis to acceleration information closest to said acceleration information derived from at least one other sensor based upon said step of comparing.

10. The method of claim 7 further including the steps of:

determining latitudinal and longitudinal calibration accelerations from GPS velocities; and

calibrating said lateral and longitudinal acceleration information with said latitudinal and longitudinal calibration accelerations.

11. The method of claim 10 further including the steps of:

update scale factors for said lateral and longitudinal acceleration information using said latitudinal and longitudinal calibration accelerations.

12. A vehicle navigation system comprising:

an orthogonal axes accelerometer providing longitudinal acceleration information and lateral acceleration information; and

said vehicle navigation system assigning an axis of said orthogonal axes accelerometer to a particular axis by comparing first and second acceleration information to acceleration measurements derived from at least one other sensor in said particular axis, and said system assigning said particular axis to said axis of said accelerometer having acceleration information closest to said acceleration information derived from at least one other sensor.

13. The vehicle navigation system of claim 12 wherein said vehicle navigation system compares the difference between said first acceleration information and said second acceleration information to a predetermined threshold to ensure the accelerations are different enough for valid axis assignment.

14. A vehicle navigation system comprising:

an orthogonal axes accelerometer providing longitudinal acceleration information and lateral acceleration information; and

said vehicle navigation system determining lateral and longitudinal calibration accelerations from GPS velocities, said system calibrating said lateral and longitudinal acceleration information with said latitudinal and longitudinal calibration accelerations.

15. The system of claim 14 wherein said system updates scale factors for said lateral and longitudinal acceleration information using said lateral and longitudinal calibration accelerations.

16. A vehicle navigation system comprising:

an orthogonal axes accelerometer providing first acceleration information along a first axis of the accelerometer and second acceleration information along a second axis of said accelerometer, said accelerometer installed in a vehicle in an unknown orientation relative to the vehicle; and

said vehicle navigation system determining the orientation of said accelerometer relative to the vehicle based upon said first acceleration information and said second acceleration information.

17. The vehicle navigation system of claim 16 wherein said vehicle navigation system compares said first and second acceleration information to acceleration measurements derived from at least one other sensor in a particular axis, and said system assigning said particular axis to said axis of said accelerometer having acceleration information closest to said acceleration information derived from at least one other sensor, said vehicle navigation system propagating a previous position to a current position based upon said first and second acceleration information.

18. A method of propagating a previous position to a current position in a vehicle navigation system, said method including the steps of:

providing longitudinal acceleration information;

providing lateral acceleration information;

deriving longitudinal speed from said longitudinal acceleration information;

deriving heading change from said lateral acceleration information and said longitudinal speed; and

using said heading change and said longitudinal acceleration to propagate a previous position to a current position;

determining latitudinal and longitudinal calibration accelerations from GPS velocities; and

calibrating said lateral and longitudinal acceleration information with said latitudinal and longitudinal calibration accelerations.

19. A method for propagating a previous position to a current position in a vehicle navigation system, said method including the steps of:

a) receiving a plurality of signals from an inertial sensor mounted in a vehicle in an unknown orientation relative to the vehicle;

b) determining said orientation of the inertial sensor relative to the vehicle based upon the plurality of signals; and

c) propagating a previous position to a current position based upon the plurality of signals.

20. The method of claim 19 wherein said step b) further includes the step of comparing the plurality of signals to acceleration measurements from at least one other sensor.