Method and apparatus for determining the geographic heading of a body

• US 6,502,055 B1
• Filed: 04/14/2000
• Issued: 12/31/2002
• Est. Priority Date: 04/28/1999
• Status: Expired due to Fees

• Current Assignee: Rafael - Armament Development Authority Ltd.
• Original Assignee: Rafael - Armament Development Authority Ltd.
• Inventors: Reiner, Jacob, Naroditsky, Michael
• Primary Examiner(s): ASSOUAD, PATRICK J
• Application Number:
  US09/549,600
• Time in Patent Office: 991 Days
• Field of Search: 702/92, 702/93, 702/141, 702/150, 734/88, 735/040.2, 701/200, 701/224
• US Class Current: 702/150
• CPC Class Codes: G01C 19/38 with north-seeking action by other than magnetic means, e.g. gyrocompasses using earth's rotation

Abstract

A method of determining an orientation of a body. The method includes the steps of measuring an acceleration of the body in a first direction, measuring an acceleration of the body in a second direction different from the first direction, the first direction and the second direction defining a plane. Measuring an acceleration perpendicular to the plane in a coordinate system rotating about an axis perpendicular to the plane, and inferring the orientation of the body from the three measurements.

Claims

1. A method of determining an orientation of a body, comprising the steps of:

(a) measuring an acceleration of the body in a first direction;

(b) measuring an acceleration of the body in a second direction different from said first direction, said first direction and said second direction defining a plane;

(c) measuring an acceleration perpendicular to said plane in a coordinate system rotating about an axis perpendicular to said plane; and

(d) inferring the orientation of the body from said three measurements.

2. The method of claim 1, wherein said first and second directions are mutually perpendicular.

3. The method of claim 1, wherein said measuring of said acceleration in said first and second directions is effected using two accelerometers mounted rigidly with respect to the body.

4. The method of claim 1, wherein said rotating coordinate system rotates at a uniform angular speed with respect to the body.

5. The method of claim 1, wherein said measuring of said acceleration in said rotating coordinate system is effected by steps including:

(i) mounting a first accelerometer at a fixed distance from said axis; and

(ii) revolving said first accelerometer about said axis.

6. The method of claim 5, wherein said measuring of said acceleration in said rotating coordinate system is effected by steps further including:

(iii) mounting a second accelerometer at said fixed distance from said axis; and

(iv) revolving said second accelerometer about said axis along with said first accelerometer.

7. The method of claim 6, wherein said first and second accelerometers are mounted on opposite sides of said axis.

8. The method of claim 1, wherein said measuring of said acceleration in said rotating coordinate system is effected at a plurality of times.

9. The method of claim 8, wherein said inferring is based on a phase of a time-dependent component of said acceleration in said rotating coordinate system.

10. A method of determining an azimuth of a body, the azimuth being defined in a certain plane, the method comprising the steps of:

(a) measuring an acceleration, perpendicular to the plane, in a coordinate system rotating about an axis perpendicular to the plane; and

(b) inferring the orientation of the body from said measured acceleration.

11. The method of claim 10, wherein said rotating coordinate system rotates at a uniform angular speed with respect to the body.

12. The method of claim 10, wherein said measuring of said acceleration is effected by steps including:

(i) mounting a first accelerometer at a fixed distance from said axis; and

(ii) revolving said first accelerometer about said axis.

13. The method of claim 12, wherein said measuring of said acceleration is effected by steps further including:

(iii) mounting a second accelerometer at said fixed distance from said axis; and

(iv) revolving said second accelerometer about said axis along with said first accelerometer.

14. The method of claim 13, wherein said first and second accelerometers are mounted on opposite sides of said axis.

15. The method of claim 10, wherein said measuring of said acceleration is effected at a plurality of times.

16. The method of claim 15, wherein said inferring is based on a phase of a time-dependent component of said acceleration.

17. An apparatus for determining an orientation of a body, comprising:

(a) a first accelerometer, fixedly mounted with respect to the body, for measuring an acceleration of the body in a first direction;

(b) a second accelerometer, fixedly mounted with respect to the body, for measuring an acceleration of the body in a second direction, said first and second directions defining a plane;

(c) a third accelerometer for measuring an acceleration in a direction perpendicular to said plane; and

(d) a mechanism for revolving said third accelerometer about an axis of revolution perpendicular to said plane.

18. The apparatus of claim 17, wherein said first and second directions are mutually perpendicular.

19. The apparatus of claim 17, further comprising:

(e) a computational mechanism for receiving signals from said accelerometers and inferring the orientation from said signals.

20. The apparatus of claim 17, further comprising:

(e) a fourth accelerometer for measuring an acceleration in said direction perpendicular to said plane, said mechanism revolving both said third accelerometer and said fourth accelerometer together about said axis.

21. The apparatus of claim 20, wherein said third and fourth accelerometers are mounted on said mechanism on opposite sides of said axis.

22. An apparatus for determining an azimuth of a body, the azimuth being defined in a certain plane, comprising:

(a) a first accelerometer, for measuring an acceleration perpendicular to the plane; and

(b) a mechanism for revolving said first accelerometer about an axis of revolution perpendicular to the plane.

23. The apparatus of claim 22, further comprising:

(c) a computational mechanism for receiving signals from said accelerometer and inferring the azimuth from said signals.

24. The apparatus of claim 22, further comprising:

(c) a second accelerometer for measuring an acceleration in said direction perpendicular to the plane, said mechanism revolving both said third accelerometer and said fourth accelerometer together about said axis of revolution.

25. The apparatus of claim 24, wherein said first and second accelerometers are mounted on said mechanism on opposite sides of said axis.