Method and apparatus for determining orientation using a plurality of angular rate sensors and accelerometers

• US 9,134,131 B2
• Filed: 04/06/2012
• Issued: 09/15/2015
• Est. Priority Date: 04/07/2011
• Status: Active Grant

• Current Assignee: Icefield Tools Corporation
• Original Assignee: Icefield Tools Corporation
• Inventors: Blake, Erik
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US13/441,765
• Publication Number:
  US 20120259579A1
• Time in Patent Office: 1,257 Days
• Field of Search: 702/151
• US Class Current: 1/1
• CPC Class Codes: E21B 47/024 of devices in the borehole determining slope or direction of the borehole E21B47/022
• CPC Class Codes: G01C 21/183 Compensation of inertial measurements, e.g. for temperature effects

Abstract

A method and apparatus for determining the orientation of an object relative to a coordinate system. The apparatus includes a body providing a reference for a local coordinate system. A rotatable sensor array is provided having more than one sensor and a rotational axis about which the rotatable sensor array rotates. A rotational drive system is provided for rotating the rotatable sensor array both to precise positions relative to the local coordinate system and at a precise rate relative to the local coordinate system. An angular position indicator to measure the angular position of the rotatable sensor array.

Claims

1. An apparatus for determining the orientation of an object relative to a geographical coordinate system, comprising:

a body providing a reference for a local coordinate system;

a rotatable sensor array having more than one sensor and a rotational axis about which the rotatable sensor array rotates with respect to the local coordinate system;

a rotational drive system for rotating the rotatable sensor array both to precise positions relative to the local coordinate system and at a precise rate relative to the local coordinate system; and

an angular position indicator to measure the angular position of the rotatable sensor array, whereby values measured in the local coordinate system are used to compute a rotation quaternion required to rotate the local coordinate system into the geographical coordinate system.

2. The apparatus of claim 1, wherein the rotatable sensor array includes three or more angular rate sensors, at least three of the angular rate sensors being mounted with their sensitive axes grossly misaligned with the rotational axis of the rotatable sensor array.

3. The apparatus of claim 2, wherein the rotatable sensor array contains two or three accelerometers.

4. The apparatus of claim 3, wherein two accelerometers are used with their sensitive axes arranged perpendicular to each other and perpendicular to the rotational axis of the rotatable sensor array.

5. The apparatus of claim 3, wherein three accelerometers are used with their sensitive axes arranged perpendicular to each other and with one sensitive axis parallel to the rotational axis of the rotatable sensor array.

6. The apparatus of claim 2, further comprising a temperature sensor that records an ambient temperature.

7. The apparatus of claim 1, wherein the body includes a non-rotatable sensor array.

8. The apparatus of claim 7, wherein the non-rotatable sensor array contains two or three accelerometers.

9. The apparatus of claim 8, wherein the non-rotatable sensor array has two accelerometers with their sensitive axes arranged perpendicular to each other and perpendicular to the rotational axis of the rotatable sensor array.

10. The apparatus of claim 8, wherein the non-rotatable sensor array has three accelerometers with their sensitive axes arranged perpendicular to each other and with one sensitive axis parallel to the rotational axis of the rotatable sensor array.

11. The apparatus of claim 8, wherein the non-rotatable sensor array contains a three-component magnetometer.

12. The apparatus of claim 8, further comprising a temperature sensor that records an ambient temperature.

13. The apparatus of claim 1, wherein the rotatable sensor array contains a three-component magnetometer.

14. The apparatus of claim 1, wherein memory is provided to record and store data from the sensors and the angular position indicator.

15. The apparatus of claim 1, further comprising a processor capable of providing an in-situ scale factor calibration.

16. A method for determining the orientation of an object relative to a geographical coordinate system, comprising:

providing a rotating sensor array with a precise rotational position relative to a local coordinate system and a precise rotational rate relative to the local coordinate system being known;

using sensor data from the rotating sensor array to produce an overdetermined system of equations that can be solved for the unknown direction of the Earth rotation vector {circumflex over (ω

)};

solving, with a measure of the gravity vector ĝ

, a rotation quaternion describing the orientation of the rotating sensor array in the local coordinate system; and

using values of ĝ and

{circumflex over (ω

)}, measured in the local coordinate system to compute a rotation quaternion required to rotate the local coordinate system into the geographical coordinate system.

17. The method of claim 16, wherein the rotating sensor array includes at least three angular rate gyro sensors positioned in at least three different orientations relative to a rotational axis of the rotating sensor array.