Three dimensional tracking system employing a rotating field

• US 5,646,524 A
• Filed: 06/16/1993
• Issued: 07/08/1997
• Est. Priority Date: 06/16/1992
• Status: Expired due to Term

• Current Assignee: Elbit Systems Limited
• Original Assignee: Elbit Ltd (IDB Holding Corporation Limited)
• Inventors: Gilboa, Pinhas
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US08/077,523
• Time in Patent Office: 1,483 Days
• Field of Search: 324/207.11, 324/207.13, 324/207.17, 324/207.22, 324/207.23, 324/207.26, 178/18, 178/19, 342/450, 342/451, 342/452
• US Class Current: 324/207.17
• CPC Class Codes: G01B 7/004 for measuring coordinates of points
• CPC Class Codes: G01C 9/06 Electric or photoelectric indication or reading means
• CPC Class Codes: G01D 5/2086 by movement of two or more coils with respect to two or more other coils

Abstract

Apparatus for determining the position and orientation of a helmet worn by a crew member in a vehicle including a generator, associated with the vehicle, which produces a rotating magnetic and electric field of fixed strength, orientation and frequency within at least a portion of the vehicle. The apparatus also includes a plurality of detectors each of which generates a signal proportional to at least one of the electric or magnetic fields at least one point associated with the helmet and calculation circuitry responsive to the signal for ascertaining the coordinates of the at least one point with respect to the generator and for determining the position and orientation of the helmet.

Claims

1. Apparatus for determining the position and orientation of an object relative to a referenced frame, comprising:

a generator, associated with the reference frame, which produces a magnetic or electric field pattern rotating about a fixed axis;

a plurality of detectors, each of which generates at least one signal responsive to at least one of the electric and magnetic fields at at least one point associated with the object; and

calculation circuitry, responsive to the at least one signal, which determines the coordinates of the at least one point associated with each of said detectors with respect to the generator based on the total field strength at the at least one point, and which determines the three-dimensional position and orientation of the object,

wherein the object is a helmet, and the computation circuitry is operative to determine the orientation of the head of a person wearing the helmet.

2. Apparatus according to claim 1 wherein each of the plurality of detectors comprises a single set of three substantially orthogonal receivers associated with a given point relative to the object, each receiver providing a signal proportional to one component of either the electric or magnetic field at the point.

3. Apparatus according to claim 1 wherein the plurality of detectors includes at least three detectors each associated with different points on the object, each detector providing at least one signal responsive to the total field strength at its associated point.

4. Apparatus according to claim 1 wherein the calculation circuitry is adapted for determining the maximum and minimum of at least one of the electric and magnetic field strength at the at least one point.

5. Apparatus according to claim 4 wherein the detectors comprise a field strength sensor associated with the at least one point.

6. Apparatus according to claim 5 wherein the field strength sensor comprises three orthogonal receivers.

7. Apparatus according to claim 6 wherein the receivers comprise dipole receiving antennas.

8. Apparatus according to claim 6 wherein the receivers comprise magnetic field sensors.

9. Apparatus according to claim 6 wherein the orthogonal receivers are electric field sensors.

10. Apparatus according to claim 1 wherein the generator comprises two dipole radiators having different orientation and phase.

11. Apparatus according to claim 10 wherein the two dipole radiators are in space and phase quadrature.

12. Apparatus according to claim 1 wherein the generator comprises a rotating static field generator.

13. Apparatus according to claim 1 wherein the calculation circuitry is adapted for determining the phase and strength of the rotating field.

14. Apparatus according to claim 13, and including a reference sensor, having a fixed position and orientation with respect to the transmitter, adapted for determining the instantaneous strength of the field at the reference sensor.

15. Apparatus according to claim 1 wherein the calculation circuitry is adapted for determining the elevation angle of the at least one point with respect to the plane of rotation of at least one of the magnetic or electric field associated with the generator.

16. Apparatus according to claim 4 wherein the calculation circuitry is operative for determining the elevation angle of the at least one point responsive to the corresponding ratios of minimum and maximum values of the field strength at the point.

17. Apparatus according to claim 1 wherein the calculation circuitry is operative for determining the distance of the at least one point from the generator.

18. Apparatus according to claim 4 wherein the calculation circuitry is operative for determining the distance of the at least one point responsive to the corresponding minimum field strength at the point.

19. Apparatus according to claim 18 wherein the distance is inversely proportional to the sixth root of the minimum of the square of the field strength.

20. Apparatus according to claim 1 wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to the plane of rotation of the field produced by the generator.

21. Apparatus according to claim 20 wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to a reference direction responsive to the corresponding field strength at the point and at a reference position.

22. Apparatus according to claim 20 wherein the calculation circuitry is operative for determining the elevation of the at least one point responsive to the minimum and maximum of the square of the field strength at the point.

23. Apparatus according to claim 20 wherein the calculation circuitry is operative for determining the azimuthal angle of the at least one point responsive to the phase difference between the time-varying portions of the square of the field strengths at the point and at the reference position.

24. Apparatus according to claim 20 wherein the calculation circuitry is operative for determining the azimuthal angle responsive to the phase difference between the measured signal at the at least one point and the drive to the generator.

25. Apparatus according to claim 1 wherein the computation circuitry is operative for determining the orientation of the detectors associated with the at least one point, responsive to the signals generated at the point and the determined field strength at that point.

26. Apparatus according to claim 1 and also including a second generator comprising a stationary dipole radiator axially oriented with the fixed axis and having a frequency different from the frequency of the rotating field.

27. Apparatus for determining the position and orientation of an object relative to a reference frame, comprising;

a generator, associated with the reference frame, which produces a magnetic or electric field pattern rotating about a fixed axis;

a plurality of detectors, each of which generates at least one signal responsive to at least one of the electric and magnetic fields at at least one point associated with the object; and

calculation circuitry, responsive to the at least one signal, which determines the coordinates of the at least one point associated with each of said detectors with respect to the generator based on the total field strength at the at least one point, and which determines the three-dimensional position and the three dimensional orientation of the object.

28. Apparatus according to claim 27 wherein each of the plurality of detectors comprise a single set of three substantially orthogonal receivers associated with a given point relative to the object, each receiver providing a signal proportional to one component of either the electric or magnetic field at the point.

29. Apparatus according to claim 27 wherein the plurality of detectors includes at least three detectors each associated with different points on the object, each detector providing at least one signal responsive to the total field strengths at its associated point.

30. Apparatus according to claim 27 wherein the calculation circuitry is adapted for determining the maximum and minimum of at least one of the electric and magnetic field strength at the at least one point.

31. Apparatus according to claim 30 wherein the detectors comprise a field strength sensor associated with the at least one point.

32. Apparatus according to claim 31 wherein the field strength sensor comprises three orthogonal receivers.

33. Apparatus according to claim 32 wherein the receivers comprise dipole receiving antennas.

34. Apparatus according to claim 32 wherein the receivers comprise magnetic field sensors.

35. Apparatus according to claim 32 wherein the orthogonal receivers are electric field sensors.

36. Apparatus according to claim 27 wherein the generator comprises a rotating static field generator.

37. Apparatus according to claim 27 wherein the calculation circuitry is adapted for determining the phase and strength of the rotating field.

38. Apparatus according to claim 37, and including a reference sensor, having a fixed position and orientation with respect to the transmitter, adapted for determining the instantaneous strength of the field at the reference sensor.

39. Apparatus according to claim 27 wherein the calculation circuitry is adapted for determining the elevation angle of the at least one point with respect to the plane of rotation of at least one of the magnetic or electric field associated with the generator.

40. Apparatus according to claim 30 wherein the calculation circuitry is operative for determining the elevation angle of the at least one point responsive to the corresponding ratios of minimum and maximum values of the field strength at the point.

41. Apparatus according to claim 27, wherein the calculation circuitry is operative for determining the distance of the at least one point from the generator.

42. Apparatus according to claim 30 wherein the calculation circuitry is operative for determining the distance of the at least one point responsive to the corresponding minimum field strength at the point.

43. Apparatus according to claim 42 wherein the distance is inversely proportional to the sixth root of the minimum of the square of the field strength.

44. Apparatus according to claim 27 wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to the plane of rotation of the field produced by the generator.

45. Apparatus according to claim 44 wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to a reference direction responsive to the corresponding field strength at the point and at a reference position.

46. Apparatus according to claim 44 wherein the calculation circuitry is operative for determining the elevation of the at least one point responsive to the minimum and maximum of the square of the field strength at the point.

47. Apparatus according to claim 45 wherein the calculation circuitry is operative for determining the azimuthal angle of the at least one point responsive to the phase difference between the time-varying portions of the square of the field strengths at the point and at the reference position.

48. Apparatus according to claim 27 wherein the calculation circuitry is operative for determining the azimuthal angle responsive to the phase difference between the measured signal at the at least one point and the square of the drive signal to the generator.

49. Apparatus according to claim 27 wherein the computation circuitry is operative for determining the orientation of the detectors associated with the at least one point, responsive to the signals generated at the point and the determined field strength at that point.

50. Apparatus according to claim 27 wherein the object is a helmet, and the computation circuitry is operative to determine the orientation of the head of a person wearing the helmet.

51. Apparatus according to claim 27 and also including a second generator comprising a stationary dipole radiator axially oriented with the fixed axis and having a frequency different form the frequency of the rotating field.

52. Apparatus for determining the position and orientation of an object relative to a reference frame, comprising:

a generator, associated with the reference frame, which produces a magnetic or electric field pattern rotating about a fixed axis;

a plurality of detectors, each of which generates at least one signal responsive to at least one of the electric and magnetic fields at at least one point associated with the object; and

calculation circuitry, responsive to the at least one signal, which determines the coordinates of the at least one point associated with each of said detectors with respect to the generator based on the total field strength at the at least one point, and which determines the three-dimensional position and orientation of the object, wherein the calculation circuitry determines the maximum and minimum of at least one of the electric and magnetic field at the at least one point and wherein the determination of the orientation is responsive to the maximum and minimum.

53. Apparatus according to claim 52 wherein each of the plurality of detectors comprises a single set of three substantially orthogonal receivers associated with a given point relative to the object, each receiver providing a signal proportional to one component of either the electric or magnetic field at the point.

54. Apparatus according to claim 52 wherein the plurality of detectors includes at least three detectors each associated with different points on the object, each detector providing a signal related to the total field strength at its associated point.

55. Apparatus according to claim 52 wherein the detectors comprise a field strength sensor associated with the at least one point.

56. Apparatus according to claim 55 wherein the field strength sensor comprises three orthogonal receivers.

57. Apparatus according to claim 56 wherein the receivers comprise dipole receiving antennas.

58. Apparatus according to claim 56 wherein the receivers comprise magnetic field sensors.

59. Apparatus according to claim 56 wherein the orthogonal receivers are electric field sensors.

60. Apparatus according to claim 52 wherein the generator comprises two dipole radiators having different orientation and phase.

61. Apparatus according to claim 60 wherein the two dipole radiators are in space and phase quadrature.

62. Apparatus according to claim 52 wherein the generator comprises a rotating static field generator.

63. Apparatus according to claim 52 wherein the calculation circuitry is adapted for determining the phase and strength of the rotating field.

64. Apparatus according to claim 63, and including a reference sensor, having a fixed position and orientation with respect to the transmitter, adapted for determining the instantaneous strength of the field at the reference sensor.

65. Apparatus according to claim 52 wherein the calculation circuitry is adapted for determining the elevation angle of the at least one point with respect to the plane of rotation of at least one of the magnetic or electric field associated with the generator.

66. Apparatus according to claim 52 wherein the calculation circuitry is operative for determining the distance of the at least one point from the generator.

67. Apparatus according to claim 66 wherein the distance is inversely proportional to the sixth root of the minimum of the square of the field strength.

68. Apparatus according to claim 52 wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to the plane of rotation of the field produced by the generator.

69. Apparatus according to claim 68 wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to a reference direction responsive to the corresponding field strength at the point and at a reference position.

70. Apparatus according to claim 68 wherein the calculation circuitry is operative for determining the elevation of the at least one point responsive to the minimum and maximum of the square of the field strength at the point.

71. Apparatus according to claim 68 wherein the calculation circuitry is operative for determining the azimuthal angle of the at least one point responsive to the phase difference between the time-varying portions of the square of the field strengths at the point and at the reference point.

72. Apparatus according to claim 68 wherein the calculation circuitry is operative for determining the azimuthal angle responsive to the phase difference between the measured signal at the at least point and the square of the drive to the generator.

73. Apparatus according to claim 52 and also including a second generator comprising a stationary dipole radiator axially oriented with the fixed axis and having a frequency different from the frequency of the rotating field.

74. Apparatus for determining the position and orientation of an object relative to a reference frame, comprising:

a generator, associated with the reference frame, which produces a magnetic or electric field pattern rotating about a fixed axis;

a plurality of detectors, each of which generates at least one signal responsive to at least one of the electric and magnetic fields at at least one point associated with the object; and

calculation circuitry, responsive to the at least one signal, which determines the coordinates of the at least one point associated with each of said detectors with respect to the generator based on the total field strength at the at least one point, and which determines the three-dimensional position and orientation of the object,

wherein the calculation circuitry is adapted for determining the phase and strength of the rotating field.

75. Apparatus according to claim 74, and including a reference sensor, having a fixed position and orientation with respect to the transmitter, adapted for determining the instantaneous strength of the field at the reference sensor.

76. Apparatus for determining the position and orientation of an object relative to a reference frame, comprising:

a generator, associated with the reference frame, which produces a magnetic or electric field pattern rotating about a fixed axis;

a plurality of detectors, each of which generates at least one signal responsive to at least one of the electric and magnetic fields at at least one point associated with the object; and

calculation circuitry, responsive to the at least one signal, which determines the coordinates of the at least one point associated with each of said detectors with respect to the generator based on the total field strength at the at least one point, and which determines the three-dimensional position and orientation of the object;

wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to the plane of rotation of the field produced by the generator.

77. Apparatus according to claim 76 wherein the calculation circuitry is operative for determining the elevation of the at least one point with respect to a reference direction responsive to the corresponding field strength at the point and at a reference position.

78. Apparatus according to claim 76 wherein the calculation circuitry is operative for determining the elevation of the at least one point responsive to the minimum and maximum of the square of the field strength at the point.

79. Apparatus according to claim 76 wherein the calculation circuitry is operative for determining the azimuthal angle of the at least one point responsive to the phase difference between the time-varying portions of the square of the field strengths at the point and at the reference position.

80. Apparatus according to claim 76 wherein the calculation circuitry is operative for determining the azimuthal angle responsive to the phase difference between the measured signal at the at least one point and the square of the drive to the generator.

81. Apparatus for determining the position and orientation of an object relative to a reference frame, comprising:

a generator, associated with the reference frame, which produces a magnetic or electric field pattern rotating about a fixed axis;

a plurality of detectors, each of which generates at least one signal responsive to at least one of the electric and magnetic fields at at least one point associated with the object; and

calculation circuitry, responsive to the at least one signal, which determines the coordinates of the at least one point associated with each of said detectors with respect to the generator based on the total field strength at the at least one point, and which determines the three-dimensional position and orientation of the object;

wherein the each of the plurality of detectors comprises a single set of three substantially orthogonal receivers associated with a given point relative to the object, each receiver providing a signal proportional to one component of either the electric or magnetic field at the point.

82. Apparatus for determining the position and orientation of an object relative to a reference frame, comprising:

a generator, associated with the reference frame, which produces a magnetic or electric field pattern rotating about a fixed axis;

a plurality of detectors, each of which generates at least one signal responsive to at least one of the electric and magnetic fields at at least one point associated with the object;

calculation circuitry, responsive to the at least one signal, which determines the coordinates of the at least one point associated with each of said detectors with respect to the generator based on the total field strength at the at least one point, and which determines the three-dimensional position and orientation of the object; and

a second generator comprising a stationary dipole radiator axially oriented with the fixed axis and having a frequency different from the frequency of the rotating field.