THREE-DIMENSIONAL, NON-CONTACTING, ANGULAR MOTION SENSOR

• US 20070295089A1
• Filed: 06/11/2007
• Published: 12/27/2007
• Est. Priority Date: 06/09/2006
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Lee, Danny, Velinsky, Steven
• Granted Patent: US 7,868,610 B2
• Time in Patent Office: Days
• US Class Current: 73/514.01
• CPC Class Codes: G01C 17/30 Earth-inductor compasses

Abstract

A three-dimensional non-contacting angular motion sensor, based on magnetometry, has been developed for velocity feedback in the ball wheel mechanism, which serves as the drivetrain for a class of omnidirectional mobile platforms. More generally, this scheme tracks rigid-body rotation about a fixed point with an undefined axis of rotation. The approach involves tracking the time-varying magnetic field of a permanent disc magnet, embedded at the center of the sphere. This data is then used to determine the absolute orientation of the magnet axis. Finally, an approach based on the natural invariants of rigid-body motion is used to determine the instantaneous axis of rotation and the angular speed of the sphere about this axis.

Claims

1. A motion tracking apparatus configured for real-time, three-dimensional angular motion tracking of an object;

wherein said object is configured to engage in spherical motion.

2. A motion tracking apparatus configured for determining, in real time and in three dimensions, an angular velocity vector of a rigid body rotating about a fixed point.

3. A motion tracking apparatus, comprising:

a sensor; and

means for determining an angular velocity vector for an object in real time;

wherein said object is configured for spherical motion; and

wherein said sensor is not in contact with said object.

4. An apparatus as recited in claim 3, further comprising:

a magnet coupled to said object;

wherein said sensor comprises a tri-axial fluxgate magnetometer.

5. An apparatus as recited in claim 3, wherein said apparatus is configured for use in biomedical applications.

6. An apparatus as recited in claim 3, wherein said apparatus is configured for use in virtual reality and game applications.

7. An apparatus as recited in claim 3, wherein said apparatus is configured for use in military aircraft applications.

8. An apparatus as recited in claim 3, wherein said apparatus is configured for use in robotic applications.

9. An apparatus as recited in claim 3, wherein said sensor is operable in harsh or demanding physical environments.

10. An apparatus as recited in claim 3, wherein said apparatus is configured for tracking continuous motion in real time.

11. An apparatus as recited in claim 3:

wherein said sensor takes a single flux density measurement, in three dimensions, of said object; and

wherein components of said angular velocity vector are determined from said single flux density measurement.

12. A motion tracking apparatus configured for determining an instantaneous axis of rotation and an angular speed for a body from a single flux density measurement, in three dimensions, of said body;

wherein said measurement is taken without physical contact of said body.

13. An apparatus as recited in claim 12, wherein said apparatus is configured to operate in complex ferromagnetic environments.

14. An apparatus, comprising:

a rigid body configured for rotational movement in three dimensions;

means for determining a trajectory of a point on said rigid body;

means for determining an angular velocity vector of said rigid body from said trajectory; and

means for outputting components of said angular velocity vector.

15. An apparatus, comprising:

a rigid body configured for rotation in three dimensions;

a magnet attached to said rigid body;

means, not in contact with said rigid body, for measuring orientation of an axis of said magnet;

means for computing real-time angular velocity data from said time-varying magnetic field measurements; and

means for outputting said real-time angular velocity data for said rigid body.

16. An apparatus, comprising:

means, not in contact with a rigid body, for motion tracking of said rigid body;

means for measuring a three-dimensional trajectory of a point on said rigid body;

means for determining an angular velocity of said rigid body from said trajectory; and

means for outputting said angular velocity of said rigid body;

wherein said rigid body is capable of rotational motion in three dimensions.

17. An apparatus, comprising:

a rigid body configured for rotation in three dimensions;

a magnet attached to said rigid body;

means, not in contact with said rigid body, for measuring a time-varying magnetic field of said magnet;

means for computing real-time angular velocity data from said time-varying magnetic field measurements; and

means for outputting said real-time angular velocity data for said rigid body.

18. A method of tracking motion of a body, wherein said body is configured to engage in spherical motion, comprising:

embedding a permanent magnet in the center of the body;

measuring the time-varying magnetic field as said magnet rotates;

determining the instantaneous magnet orientation from said field measurements; and

outputting angular motion data for the body.

19. A method, comprising:

measuring a three-dimensional trajectory of a point on a rigid body;

determining an angular velocity of said rigid body from said trajectory; and

outputting said angular velocity of said rigid body;

wherein said rigid body is capable of rotational motion in three dimensions.