System for three dimensional positioning and tracking

• US 20030120448A1
• Filed: 12/04/2002
• Published: 06/26/2003
• Est. Priority Date: 02/08/2001
• Status: Active Grant

• Current Assignee: Nemor Properties LLC (Intellectual Ventures LLC)
• Original Assignee: Netmor Ltd.
• Inventors: Primack, Harel, Moriya, Netzer, Itzkovich, Moti
• Granted Patent: US 6,912,475 B2
• Time in Patent Office: Days
• US Class Current: 702/95
• CPC Class Codes: G06T 7/277 involving stochastic approaches, e.g. using Kalman filters
• CPC Class Codes: G06V 40/23 Recognition of whole body movements, e.g. for sport training

Abstract

A system for tracking and positioning a moving object, the system including a plurality of transmitters operative to transmit alternating electromagnetic fields within a three-dimensional space and at least one sensor arranged to be fixed to at least one corresponding portion of a moving object whose position it is sought to monitor. Each of said at least one sensors includes an electromagnetic field receiver having at least one active axis and operative to receive at least one component, lying along the at least one active axis respectively, of the alternating electromagnetic fields, an accelerometer to independently measure at least one component of the acceleration of the moving object; and a digital signal processor. The digital signal processor is adapted to store at least one characteristic of the electromagnetic fields as received by the electromagnetic field receiver, and at least one characteristic of the acceleration as measured by the accelerometer, and to transmit the stored characteristics to a Kalman filter, and to compute therefrom an estimate of at least one component of the position and orientation of the moving object.

Claims

1. A system for tracking and positioning a moving object, the system comprising:

a plurality of transmitters operative to transmit alternating electromagnetic fields within a three-dimensional space; and

at least one sensor arranged to be fixed to at least one corresponding portion of a moving object whose position it is sought to monitor, each of said at least one sensors comprising;

an electromagnetic field receiver having at least one active axis and operative to receive at least one component, lying along the at least one active axis respectively, of the alternating electromagnetic fields;

an accelerometer to independently measure at least one component of the acceleration of the moving object; and

a digital signal processor adapted to store at least one characteristic of the electromagnetic fields as received by the electromagnetic field receiver, and at least one characteristic of the acceleration as measured by the accelerometer, and to transmit the stored characteristics to a Kalman filter, and to compute therefrom an estimate of at least one component of the position and orientation of the moving object.

2. A system according to claim 1 wherein said at least one component of the position of the moving object comprises at least two components.

3. A system according to claim 2 wherein said at least two components of the position of the moving object comprise three components.

4. A system according to claim 1 wherein said at least one component of the position of the moving object is selected from the group consisting of the x, y, and z coordinates of the moving object.

5. A system according to claim 1 wherein said at least one component of the acceleration of the moving object comprises at least two components.

6. A system according to claim 5 wherein said at least two components of the acceleration of the moving object comprise three components.

7. A system according to claim 1 wherein said at least one component of the acceleration of the moving object is selected from the group consisting of the a_x, a_y, and a_z acceleration components of the moving object.

8. A system according to claim 1 wherein the Kalman filter employs at least one estimate of an acceleration value'"'"'s components in order to compute an estimate of said at least one component of the moving object'"'"'s position and orientation, and wherein the Kalman filter employs said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components, rather then deriving said at least one estimated acceleration value'"'"'s components from the electromagnetic field information.

9. A system according to claim 8 wherein employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components improves the accuracy of the estimate of the at least one component of the position and orientation of the moving object.

10. A system according to claim 8 wherein the electromagnetic field receiver comprises a single axis electromagnetic field receiver, and wherein the accelerometer is attached thereto, such that employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components provides information about the axial rotation of the moving object.

11. A system for indicating a disturbance in an electromagnetic field, the system comprising:

a plurality of transmitters operative to transmit alternating electromagnetic fields within a three-dimensional space; and

at least one sensor arranged to be fixed to at least one corresponding portion of a moving object whose position it is sought to monitor, each of said at least one sensors comprising;

an electromagnetic field receiver having at least one active axis and operative to receive at least one component, lying along the at least one active axis respectively, of the alternating electromagnetic fields;

an accelerometer operative to independently measure at least one component of the acceleration of the moving object; and

a digital signal processor for storing at least one characteristic of the electromagnetic fields as received by the electromagnetic field receiver, and at least one characteristic of the acceleration as measured by the accelerometer,

wherein said digital signal processor is adapted to

transmit the at least one stored characteristic of the electromagnetic fields to a Kalman filter and calculate therefrom a first estimate of at least one component of the position and orientation of the moving object;

transmit the at least one stored characteristics of the electromagnetic field and the at least one characteristic of the acceleration as measured by the accelerometer to the Kalman filter, and calculate therefrom a second estimate of at least one component of the position and orientation of the moving object; and

compare said first and second estimates for a discrepancy indicating a disturbance in the electromagnetic field.

12. A system according to claim 11 wherein said digital signal processor compares said first and second estimates for a discrepancy indicating a disturbance in the electromagnetic field on a periodic basis.

13. A system according to claim 11, wherein a discrepancy indicating a disturbance in the electromagnetic field comprises a discrepancy of greater than the expected absolute accuracy of the measurement of the position and orientation of the moving object.

14. A system according to claim 11 wherein said at least one component of the position of the moving object comprises at least two components.

15. A system according to claim 14 wherein said at least two components of the position of the moving object comprise three components.

16. A system according to claim 11 wherein said at least one component of the position of the moving object is selected from the group consisting of the x, y, and z coordinates of the moving object.

17. A system according to claim 11 wherein said at least one component of the acceleration of the moving object comprises at least two components.

18. A system according to claim 17 wherein said at least two components of the acceleration of the moving object comprise three components.

19. A system according to claim 11 wherein said at least one component of the acceleration of the moving object is selected from the group consisting of the a_x, a_y, and a_z acceleration components of the moving object.

20. A system according to claim 11 wherein the Kalman filter calculating the second estimate of at least one component of the position and orientation of the moving object employs at least one estimate of an acceleration value'"'"'s components in order to compute an estimate of said at least one component of the moving object'"'"'s position and orientation, and wherein the Kalman filter employs said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components, rather then deriving said at least one estimated acceleration value'"'"'s components from the electromagnetic field information.

21. A system according to claim 20 wherein employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components improves the accuracy of the estimate of the at least one component of the position and orientation of the moving object.

22. A system according to claim 20 wherein the electromagnetic field receiver comprises a single axis electromagnetic field receiver, and wherein the accelerometer is attached thereto, such that employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components provides information about the axial rotation of the moving object.

23. A method for tracking and positioning a moving object, the method comprising:

positioning a plurality of transmitters operative to transmit alternating electromagnetic fields within a three-dimensional space;

affixing at least one sensor to at least one corresponding portion of the moving object whose position it is sought to monitor, each of said at least one sensors comprising;

an electromagnetic field receiver having at least one active axis and operative to receive at least one component, lying along the at least one active axis respectively, of the alternating electromagnetic fields; and

an accelerometer operative to independently measure at least one component of the acceleration of the moving object; and

storing at least one characteristic of the electromagnetic fields as received by the electromagnetic field receiver, and at least one characteristic of the acceleration as measured by the accelerometer, transmitting the stored characteristics to a Kalman filter, and computing therefrom an estimate of at least one component of the position and orientation of the moving object.

24. A method according to claim 23 wherein said at least one component of the position of the moving object comprises at least two components.

25. A method according to claim 24 wherein said at least two components of the position of the moving object comprise three components.

26. A method according to claim 23 wherein said at least one component of the position of the moving object is selected from the group consisting of the x, y, and z coordinates of the moving object.

27. A method according to claim 23 wherein said at least one component of the acceleration of the moving object comprises at least two components.

28. A method according to claim 27 wherein said at least two components of the acceleration of the moving object comprise three components.

29. A method according to claim 23 wherein said at least one component of the acceleration of the moving object is selected from the group consisting of the a_x, a_y, and a_z acceleration components of the moving object.

30. A method according to claim 23 and also comprising employing at least one estimate of an acceleration value'"'"'s components in order to compute an estimate of said at least one component of the moving object'"'"'s position and orientation, and wherein said at least one independently measured component of the acceleration of the moving object is employed as said at least one estimated acceleration value'"'"'s components, rather then deriving said at least one estimated acceleration value'"'"'s components from the electromagnetic field information.

31. A method according to claim 30 wherein employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components improves the accuracy of the estimate of the at least one component of the position and orientation of the moving object.

32. A method according to claim 30 wherein the electromagnetic field receiver comprises a single axis electromagnetic field receiver, and wherein the accelerometer is attached thereto, such that employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components provides information about the axial rotation of the moving object.

33. A method for indicating a disturbance in an electromagnetic field, the method comprising:

positioning a plurality of transmitters operative to transmit alternating electromagnetic fields within a three-dimensional space; and

affixing at least one sensor to at least one corresponding portion of a moving object whose position it is sought to monitor, each of said at least one sensors comprising;

an electromagnetic field receiver having at least one active axis and operative to receive at least one component, lying along the at least one active axis respectively, of the alternating electromagnetic fields; and

an accelerometer operative to independently measure at least one component of the acceleration of the moving object;

storing at least one characteristic of the electromagnetic fields as received by the electromagnetic field receiver, and at least one characteristic of the acceleration as measured by the accelerometer, transmitting the at least one stored characteristic of the electromagnetic fields to a Kalman filter and calculating therefrom a first estimate of at least one component of the position and orientation of the moving object;

transmitting the at least one stored characteristics of the electromagnetic field and the at least one characteristic of the acceleration as measured by the accelerometer to the Kalman filter, and calculating therefrom a second estimate of at least one component of the position and orientation of the moving object; and

comparing said first and second estimates for a discrepancy indicating a disturbance in the electromagnetic field.

34. A method according to claim 33 wherein said comparing said first and second estimates for a discrepancy indicating a disturbance in the electromagnetic field occurs on a periodic basis.

35. A method according to claim 33, wherein a discrepancy indicating a disturbance in the electromagnetic field comprises a discrepancy of greater than the expected absolute accuracy of the measurement of the position and orientation of the moving object.

36. A method according to claim 33 wherein said at least one component of the position of the moving object comprises at least two components.

37. A method according to claim 36 wherein said at least two components of the position of the moving object comprise three components.

38. A method according to claim 33 wherein said at least one component of the position of the moving object is selected from the group consisting of the x, y, and z coordinates of the moving object.

39. A method according to claim 33 wherein said at least one component of the acceleration of the moving object comprises at least two components.

40. A method according to claim 39 wherein said at least two components of the acceleration of the moving object comprise three components.

41. A method according to claim 33 wherein said at least one component of the acceleration of the moving object is selected from the group consisting of the a_x, a_y, and a_z acceleration components of the moving object.

42. A method according to claim 33 wherein calculating the second estimate of at least one component of the position and orientation of the moving object comprises employing at least one estimate of an acceleration value'"'"'s components in order to compute an estimate of said at least one component of the moving object'"'"'s position and orientation, and employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components, rather then deriving said at least one estimated acceleration value'"'"'s components from the electromagnetic field information.

43. A method according to claim 42 wherein employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components improves the accuracy of the estimate of the at least one component of the position and orientation of the moving object.

44. A method according to claim 42 wherein the electromagnetic field receiver comprises a single axis electromagnetic field receiver, and wherein the accelerometer is attached thereto, such that employing said at least one independently measured component of the acceleration of the moving object as said at least one estimated acceleration value'"'"'s components provides information about the axial rotation of the moving object.