SENSOR-BASED ORIENTATION SYSTEM

• US 20120004882A1
• Filed: 07/08/2011
• Published: 01/05/2012
• Est. Priority Date: 03/15/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sheynblat, Leonid
• Granted Patent: US 8,910,522 B2
• Time in Patent Office: Days
• US Class Current: 702/141
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A method for measuring positional changes of an object, including rotation about any or all of three axes, using linear accelerometers. There is disclosed a method of using a linear accelerometer to integrate two 3D linear accelerometers in order to measure and supply for further use six-dimensional information, that is, translation in three dimensions and rotation about three axes. Two linear accelerometer sensors are used to determine all but rotation about an imaginary axis between the accelerometers. Output from a third accelerometer may be used to generate the data needed to determine rotation about the imaginary axis. The need for a gyroscope for detecting changes in heading (i.e., yaw or azimuth) may therefore be avoided.

Claims

1. A method for determining movement of an object in six degrees of freedom, the method comprising:

providing a first linear accelerometer and a second linear accelerometer disposed on an imaginary axis relative to the object, wherein at least one axis of sensitivity of the first linear accelerometer is parallel to at least one axis of sensitivity of the second linear accelerometer;

measuring, with the first linear accelerometer, a first linear movement of the object in relation to an x-y-z coordinate system;

measuring, with the second linear accelerometer, a second linear movement of the object in relation to the x-y-z coordinate system; and

measuring with the first linear accelerometer and the second linear accelerometer an angular rotation of the object in relation to three axes of rotation in the x-y-z coordinate system, wherein the imaginary axis is not parallel with any axes in the x-y-z coordinate system.

2. The method of claim 1, wherein angular rotation about the imaginary axis between the first linear accelerometer and the second linear accelerometer is not fully detectable.

3. The method of claim 1, wherein the first linear accelerometer has a first local horizontal plane and the second linear accelerometer has a second local horizontal plane that is co-planar with or parallel with the first local horizontal plane.

4. The method of claim 1, further comprising:

providing a third linear accelerometer that is off the imaginary axis;

measuring, with the third linear accelerometer, a third linear movement of the object in relation to an x-y-z coordinate system; and

measuring with the first linear accelerometer, the second linear accelerometer, and the third linear accelerometer, angular rotation about the imaginary axis.

5. The method of claim 1, further comprising:

determining, with measurements from the first linear accelerometer and the second linear accelerometer, a change in position of the object; and

determining, with measurements from the first linear accelerometer and the second linear accelerometer, a change in orientation of the object.

6. The method of claim 5, wherein the act of determining the change in orientation comprises comparing respective outputs of the first linear accelerometer and the second linear accelerometer relative to an accelerometer axis of sensitivity.

7. The method of claim 5, further comprising:

assigning a first initial coordinate for the first linear accelerometer and a second initial coordinate for the second linear accelerometer at a first time;

reading data from the first linear accelerometer between the first time and a second time;

reading data from the second linear accelerometer between the first time and a third time;

determining a new first coordinate for the first linear accelerometer at the second time using the first initial coordinate and the data from the first linear accelerometer between the first time and a second time; and

determining a new second coordinate for the second linear accelerometer at the third time using the second initial coordinate and the data from the second linear accelerometer between the first time and a third time;

using the new first coordinate for the first linear accelerometer and the new second coordinate for the second linear accelerometer to determine the change in position of the object and the change in orientation of the object.

16. The method of claim 7, wherein the second time and the third time are a same time.

8. An apparatus for determining movement of an object in six degrees of freedom, comprising:

a first linear accelerometer having three axes of sensitivity;

a second linear accelerometer having three axes of sensitivity and positioned with respect to the first linear accelerometer to define an imaginary axis, wherein at least one axis of sensitivity of the first linear accelerometer is parallel to at least one axis of sensitivity of the second linear accelerometer;

means for measuring, with the first linear accelerometer and the second linear accelerometer, the linear movement of the object in relation to an x-y-z coordinate system; and

means for measuring, with the first linear accelerometer and the second linear accelerometer, an angular rotation of the object in relation to three axes of rotation in the x-y-z coordinate system, wherein the imaginary axis is not parallel with any axes in the x-y-z coordinate system.

9. The apparatus of claim 8, wherein the means for measuring, with the first linear accelerometer and the second linear accelerometer, the angular rotation of the object in relation to three axes of rotation in the x y z coordinate system does not measure angular rotation about the imaginary axis between the first linear accelerometer and the second linear accelerometer.

10. The apparatus of claim 8, wherein the first linear accelerometer has a first local horizontal plane and the second linear accelerometer has a second local horizontal plane that is co-planar with or parallel with the first local horizontal plane.

11. The apparatus of claim 8, further comprising:

a third linear accelerometer that is off the imaginary axis; and

measuring, with the third linear accelerometer, a third linear movement of the object in relation to an x-y-z coordinate system;

wherein the means for measuring, with the first linear accelerometer and the second linear accelerometer, an angular rotation of the object in relation to three axes of rotation in the x-y-z coordinate system further uses the third linear accelerometer for measuring an angular rotation about the imaginary axis.

12. The apparatus of claim 8 further comprising:

a processing unit to determine, from the measurements from the first linear accelerometer and the second linear accelerometer, a changes in a position and an orientation of the object.

13. The apparatus of claim 12, wherein the means for measuring, with the first linear accelerometer and the second linear accelerometer, the linear movement of the object comprises means for comparing respective outputs of the first linear accelerometer and the second linear accelerometer relative to an accelerometer axis of sensitivity.

14. The apparatus of claim 12, wherein the processing unit assigns initial coordinates to each of the first linear accelerometer and the second linear accelerometer at a first time, determines new coordinates for each of the first linear accelerometer and the second linear accelerometer at a subsequent time, and computes the changes in position and orientation of the object using the new coordinates for each of the first linear accelerometer and the second linear accelerometer at the subsequent time.

15. A computer program product for enabling a computer to determine movement of an object in six degrees of freedom comprising:

software instructions for enabling the computer to perform predetermined operations; and

a computer readable storage medium bearing the software instructions;

the predetermined operations including;

receiving information from a first linear accelerometer and a second linear accelerometer disposed on an imaginary axis relative to the object, wherein at least one axis of sensitivity of the first linear accelerometer is parallel to at least one axis of sensitivity of the second linear accelerometer;

determining, with the information from the first linear accelerometer, a first linear movement of the object in relation to an x-y-z coordinate system;

determining, with the information from the second linear accelerometer, a second linear movement of the object in relation to the x-y-z coordinate system;

determining with the information from the first linear accelerometer and the second linear accelerometer an angular rotation of the object in relation to three axes of rotation in the x-y-z coordinate system, wherein the imaginary axis is not parallel with any axes in the x-y-z coordinate system;

determining, with the first linear movement and the second linear movement, a change in position of the object; and

determining, with the angular rotation, a change in orientation of the object, wherein the computer determines changes in orientation of the object in six degrees of freedom.