Method and apparatus for inertial guidance for an automobile navigation system

• US 6,282,496 B1
• Filed: 10/29/1999
• Issued: 08/28/2001
• Est. Priority Date: 10/29/1999
• Status: Active Grant

• Current Assignee: TomTom Navigation B.V (TomTom NV)
• Original Assignee: Visteon Technologies LLC (Visteon Corporation)
• Inventors: Chowdhary, Mahesh
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): Tran, Dalena
• Application Number:
  US09/430,557
• Time in Patent Office: 669 Days
• Field of Search: 701/213, 701/217, 701/220, 701/221, 701/214, 701/41, 342/357.08, 342/357.14, 342/457
• US Class Current: 701/220
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network

Abstract

The present invention discloses an improved vehicular inertial guidance navigation system, a.k.a. a dead reckoning system for navigation of a vehicle. The inertial guidance navigation system which may be used alone or in combination with other position determination means, such as GPS and map databases, to determine the location of a vehicle. The dead reckoning system has several advantages over existing systems. First, it can be easily mounted to the chassis of any vehicle. Second, it does not require any interface with existing sensors on the vehicle. Third, the system contains logic for removing errors in the position and heading determinations, brought about by angulation/rotation of the chassis and inertial guidance sensors, brought about by inclination or tilt of the chassis, with respect to an inertial/quasi-inertial frame of reference, such as the earth. The inertial guidance system includes: an inertial guidance sensor, a translation unit, and a logic unit. The inertial guidance sensor is suitable for coupling to the vehicle. The inertial guidance sensor senses motion of the vehicle in a non-inertial frame of reference and forming a sensor signal corresponding thereto. The translation unit is coupled to receive the sensor signal formed by the inertial guidance sensor. The translation unit translates the sensor signal into a quasi-inertial frame of reference and forms a translated signal corresponding thereto. The logic unit receives the translated signal formed by the translation unit and converts converting the translated signal into an estimated position and heading of the vehicle.

Claims

1. An inertial guidance system for navigation of a vehicle having a body plane angle associated therewith, said inertial guidance system comprising:

an inertial guidance sensor for coupling to the vehicle, and for sensing motion of the vehicle in a non-inertial frame of reference and forming an angular motion signal and an acceleration signal corresponding thereto;

a frame transformation unit coupled to receive the angular motion and acceleration signals, correct the angular motion signal using body plane angle data derived from the acceleration signal, and correct the acceleration signal using a rotation matrix representing the corrected angular motion signal, thereby transforming the angular motion and acceleration signals into a quasi-inertial frame of reference; and

a logic unit coupled to receive the corrected angular motion and acceleration signals formed by said frame transformation unit, said logic unit for converting the corrected angular motion and acceleration signals into an estimated position and heading of the vehicle.

2. The inertial guidance system of claim 1, wherein the inertial guidance sensor further comprises:

an acceleration sensor for coupling to the vehicle, and the acceleration sensor forming a z axis raw acceleration signal and an x axis raw acceleration signal, and the z axis raw acceleration signal corresponding to an acceleration of the vehicle along a z axis substantially normal to a chassis of the vehicle, and the x axis raw acceleration signal corresponding to an acceleration of the vehicle along an x axis substantially aligned with a direction of motion of the vehicle.

3. The inertial guidance system of claim 1, wherein the inertial guidance sensor further comprises:

an angular rate sensor to measure an angular rotation rate of the vehicle; and

an accelerometer to measure an acceleration of the vehicle.

4. The inertial guidance system for vehicle navigation of claim 3, wherein the angular rate sensor comprises at least one of:

an inclinometer and an angular rate sensor together with an integrator.

5. The inertial guidance system of claim 1, wherein the angular motion signal represents angular rotation of the vehicle in a non-inertial frame of reference and the acceleration signal represents an acceleration of the vehicle in a non-inertial frame of reference.

6. The inertial guidance system for vehicle navigation of claim 1, wherein the the body plane angle data is derived from the projections into the acceleration signal of at least one of a gravitational constant and a magnitude of a gravity vector at a location of the vehicle.

7. The inertial guidance system for vehicle navigation of claim 1, wherein the logic unit comprises at least one of:

a Kalman filter and a covariance filter.

8. The inertial guidance system of claim 5, wherein the body plane angle data is derived from the projections into the acceleration signal of at least one of a gravitational constant and a magnitude of a gravity vector at a location of the vehicle;

and wherein the angular motion signal is corrected in an inertial rotation module by a scale factor corresponding with the body plane angle.

9. The inertial guidance system for vehicle navigation of claim 8, wherein in a rotation matrix module the acceleration signal is corrected by matrix multiplication of the rotation matrix and an acceleration matrix representing the acceleration signal.

10. A hybrid system for navigation of a vehicle having a body plane angle associated therewith, said hybrid system comprising:

an inertial guidance sensor for coupling to the vehicle, and for sensing motion of the vehicle in a non-inertial frame of reference and forming an angular motion signal and an acceleration signal corresponding thereto;

a frame transformation unit coupled to receive the angular motion and acceleration signals, correct the angular motion signal using body plane angle data derived from the acceleration signal, and correct the acceleration signal using a rotation matrix representing the corrected angular motion signal, thereby transforming the angular motion and acceleration signals into a quasi-inertial frame of reference;

a first logic unit coupled to receive the corrected angular motion and acceleration signals formed by said frame transformation unit, said logic unit for converting the corrected angular motion and acceleration signals into a first estimated position and heading of the vehicle;

a position and heading determination means for forming a second estimated position and heading of the vehicle; and

a second logic unit coupled to receive the first estimated position and heading signal formed by the first logic unit, together with the second estimated position and heading signal formed by said position and heading determination means and for estimating the position and heading of the vehicle therefrom.

11. The hybrid system for navigation of a vehicle of claim 10, wherein said first logic unit comprises at least one of:

a Kalman filter and a covariance filter.

12. The hybrid system for navigation of a vehicle of claim 10, wherein said second position and heading determination means comprises at least one of:

a GPS system, a WAAS system and a map database together with map matching processes.

13. A hybrid system for navigation of a vehicle, and said hybrid system comprising:

an inertial guidance sensor for coupling to the vehicle, and for sensing motion of the vehicle in a non-inertial frame of reference and forming sensor signals corresponding thereto;

a frame transformation unit coupled to receive the sensor signals formed by the inertial guidance sensor, said frame transformation unit for transforming the sensor signals into a quasi-inertial frame of reference and forming a first signal corresponding to an acceleration of the vehicle in a quasi-inertial reference frame and an angulation of the vehicle in a quasi-inertial reference frame;

a first logic unit coupled to receive the first signal formed by said frame transformation unit, said logic unit for converting the first signal into a first estimated position and heading of the vehicle;

a position and heading determination means for forming a second estimated position and heading of the vehicle, said position and heading determination means having a map database together with map matching processes, and said map database including data corresponding to inclinations for each of a plurality of road segments; and

a second logic unit coupled to receive the first estimated position and heading signal formed by the first logic unit, together with the second estimated position and heading signal formed by said position and heading determination means and for estimating the position and heading of the vehicle therefrom,

wherein said frame transformation unit utilizes said inclinations for a road segment corresponding with a location of the vehicle, for transforming a portion of the first signal corresponding to the angulation of the vehicle.

14. The hybrid system for navigation of a vehicle of claim 13,

wherein said second position and heading determination means includes a map database together with map matching processes, and said map database including data corresponding to inclinations for each of a plurality of road segments;

wherein said sensor signals include an acceleration signal corresponding to the acceleration of the vehicle in a non-inertial frame of reference and an angular signal corresponding to the angle of the vehicle in a non-inertial frame of reference; and

wherein said frame transformation unit derives from the acceleration signal a gravity angle corresponding to the angle with respect to the gravity vector of the non-inertial frame of reference, and further utilizes inclinations for a road segment corresponding with a location of the vehicle to modify a gain factor applied to the combination of the gravity angle with the angulation signal to generate the portion of the first signal corresponding to the angulation of the vehicle in a quasi-inertial reference frame.

15. The hybrid system for navigation of a vehicle of claim 14, wherein said frame transportation unit further utilizes at least one of:

a history of the effect of each gain factor on calculated angles for common maneuvers, a data corresponding to a particular driving style to modify the gain factor.

16. A method for navigating a vehicle having a body plane angle associated therewith comprising the acts of:

detecting an initial position and an initial heading of the vehicle;

sensing a motion of the vehicle in a non-inertial frame of reference and generating an angular motion signal and an acceleration signal corresponding to the motion;

transforming the motion sensed into motion within a quasi-inertial frame of reference by correcting the angular motion signal using body plane angle data derived from the acceleration signal, and correcting the acceleration signal using a rotation matrix representing the corrected angular motion signal;

converting the motion within a quasi-inertial frame of reference into a position change and a heading change; and

adding the position change to the initial position and the heading change to the initial heading to form respectively an updated position estimate and an updated heading estimate.

17. The method for navigating a vehicle of claim 16,

wherein the acceleration signal is generated by sensing along a first axis substantially normal to a chassis of the vehicle and a second axis substantially aligned with a direction of travel of the vehicle; and

wherein the body plane angle is derived from the acceleration signal by projecting the first axis and the second axis into a quasi-inertial frame of reference such that the projected acceleration of the vehicle along the first axis in the quasi-inertial frame of reference corresponds to at least one of a gravitational constant and a magnitude of a gravity vector at a location of the vehicle.

18. The method for navigating a vehicle of claim 16,

wherein the sensing act further comprises the acts of:

measuring an acceleration of the vehicle in a non-inertial frame of reference;

measuring an angular motion of the vehicle in the non-inertial frame of reference; and

wherein the transforming act further comprises the acts of;

correlating a vertical component of the acceleration of the vehicle measured in said first measuring act with at least one of a gravitational constant and a magnitude of a gravity vector at a location of the vehicle;

generating a gravity angle responsive to said correlating act and the gravity angle corresponding to an angular rotation of the non-inertial reference frame with respect to a quasi-inertial reference frame; and

correcting the angular motion of the vehicle sensed in said second measuring act by an amount corresponding with the gravity angle.

19. The method for navigating a vehicle of claim 18, further comprising the act of:

multiplying the rotation matrix corresponding to a corrected angular motion of the vehicle determined in said correcting act with an acceleration matrix corresponding to the acceleration of the vehicle determined in said first measuring act.

20. A computer program product for navigating a vehicle, and the computer program product comprising:

a computer-readable storage medium having computer-readable program code means embodied in the medium, the computer-readable program code means comprising;

computer-readable program code means for detecting an initial position and an initial heading of the vehicle;

computer-readable program code means for sensing a motion of the vehicle in a non-inertial frame of reference and generating an angular motion signal and an acceleration signal corresponding to the motion;

computer-readable program code means for transforming the motion senses in said act of sensing into motion within quasi-inertial frame of reference by correcting the angular motion signal using body plane angle data derived from the acceleration signal, and correcting the acceleration signal using a rotation matrix representing the corrected angular motion signal;

computer-readable program code means for converting the motion with a quasi-inertial frame of reference into a position change and a heading change; and

computer-readable program code means for adding the position change to the initial position and the heading change to the initial heading to form respectively an updated position estimate and an updated heading estimate.

21. The computer readable program product of claim 20,

wherein the computer-readable program code means for sensing a motion further comprises:

computer-readable program code means for sensing an acceleration of the vehicle along a first axis substantially normal to a chassis of the vehicle and a second axis substantially aligned with a direction of travel of the vehicle to generate the acceleration signal; and

wherein the computer-readable program code means for transforming further comprises;

computer-readable program code means for projecting the first axis and the second axis into a quasi-inertial frame of reference such that the projected acceleration of the vehicle along the first axis in the quasi-inertial frame of reference corresponds to at least one of;

a gravitational constant and a magnitude of a gravity vector at a location of the vehicle.

22. The computer readable program product of claim 20,

wherein the computer-readable program code means for sensing further comprises:

computer-readable program code means for sensing an acceleration of the vehicle along a first axis substantially normal to a chassis of the vehicle and a second axis substantially aligned with a direction of travel of the vehicle to generate the acceleration signal; and

wherein the computer-readable program code means for transforming further comprises;

computer-readable program code means for deriving the body plane angle from the acceleration signal by projecting the first axis and the second axis into a quasi-inertial frame of reference such that the projected acceleration of the vehicle along the first axis in the quasi-inertial frame of reference corresponds to at least one of;

a gravitational constant and a magnitude of a gravity vector at a location of the vehicle; and

computer-readable program code means for subtracting the body plane angle derived and corresponding to a rotation of the chassis of the vehicle relative to the quasi-inertial frame of reference from the angular motion of the vehicle sensed.