Electromagnetic field source with detection of position of secondary coil in relation to multiple primary coils

• US 6,212,430 B1
• Filed: 05/03/1999
• Issued: 04/03/2001
• Est. Priority Date: 05/03/1999
• Status: Expired due to Term

• Current Assignee: Abiomed, Inc. (Johnson & Johnson)
• Original Assignee: Abiomed, Inc. (Johnson & Johnson)
• Inventors: Kung, Robert T. V.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/304,198
• Time in Patent Office: 701 Days
• Field of Search: 607/32-34, 607/30, 607/60, 607/61, 128/903
• US Class Current: 607/61
• CPC Class Codes: A61M 2205/8243 by induction
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/196 replacing the entire heart, e.g. total artificial hearts [TAH]
• CPC Class Codes: A61M 60/216 including a rotating member acting on the blood, e.g. impeller
• CPC Class Codes: A61M 60/247 Positive displacement blood pumps
• CPC Class Codes: A61M 60/873 specially adapted for wireless or transcutaneous energy transfer [TET], e.g. inductive charging
• CPC Class Codes: A61M 60/875 specially adapted for optimising alignment of external and implantable coils
• CPC Class Codes: A61M 60/876 Implantable batteries
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

An electromagnetic field source (EFS) for providing electromagnetic energy to a secondary coil, including two or more primary coils that each carry a time-varying current to produce an electromagnetic field, and a controller that selectively provides current to one or more primary coils based on their position with respect to the secondary coil. The secondary coil may be implanted in a human recipient and used to provide power for the operation of a medical device, such as an artificial heart or ventricular assist device. The invention also provides such a secondary coil and EFS, collectively referred to as a transcutaneous energy transfer (TET) device. The primary coils of the EFS or TET may be housed in furniture. For example, they may be housed in a bed mattress or mattress pad on which the recipient rests, or in a blanket for covering the recipient. The controller includes a proximity detector that identifies those primary coils that are closest to the secondary coil, and a current director that, responsive to the proximity detector, selectively directs time-varying currents through the closest primary coils. The controller may also include an orientation detector, coupled to the current director, that determines an orientation of the secondary coil with respect to the closest primary coils. In one implementation, the proximity detector identifies the quantity of closest primary coils utilizing a resonance frequency shift detector that detects a shift in inductance of one or more primary coils due to the proximity of the secondary coil.

Claims

1. An electromagnetic field source for providing electromagnetic energy to a secondary coil, comprising:

a plurality of primary coils, each constructed and arranged to carry a time-varying current to produce an electromagnetic field; and

a controller constructed and arranged to detect a position and orientation of the secondary coil relative to one or more of the plurality of primary coils and to selectively provide current to one or more of the plurality of primary coils based on the position and orientation of the secondary coil relative to the primary coils.

2. The electromagnetic field source of claim 1, wherein the controller comprises:

a proximity detector constructed and arranged to identify a quantity of the plurality of primary coils that are closest to the secondary coil; and

a current director, responsive to the proximity detector and electrically coupled to the plurality of primary coils, constructed and arranged to selectively direct time-varying currents through the closest primary coils.

3. The electromagnetic field source of claim 2, wherein:

the quantity of closest primary coils identified by the proximity detector is a predetermined value.

4. The electromagnetic field source of claim 2, wherein:

the quantity of closest primary coils identified by the proximity detector is based on a size of the secondary coil.

5. The electromagnetic field source of claim 2, wherein:

each primary coil is disposed in a plane substantially parallel to, including the same plane as, a plane of each of the other primary coils.

6. The electromagnetic field source of claim 5, wherein the primary coils are disposed in two or more substantially parallel planes, including:

a first plane having one or more first-plane primary coils that, when energized, generate electromagnetic fields having one or more dead zones; and

a second plane having at least one second-plane primary coil positioned with respect to the two or more mutually adjacent first-plane primary coils to generate, when energized, at least one electromagnetic field encompassing the one or more dead zones.

7. The electromagnetic field source of claim 5, wherein the primary coils are disposed in two or more substantially parallel planes, including:

a first plane having two or more mutually adjacent first-plane primary coils; and

a second plane having at least one second-plane primary coil positioned with respect to the two or more mutually adjacent first-plane primary coils so that the projection of a magnetic center of the second-plane primary coil on the first plane is approximately equidistant from magnetic centers of each of the two or more mutually adjacent first-plane primary coils.

8. The electromagnetic field source of claim 5, wherein the primary coils are disposed in two or more substantially parallel planes, including:

a first plane having four mutually adjacent primary coils positioned with respect to each other in a roughly square arrangement; and

a second plane having one primary coil positioned so that the projection of its geometric center on the first plane is approximately centrally located among the four first-plane primary coils.

9. The electromagnetic field source of claim 5, wherein the controller comprises:

an orientation detector, coupled to the current director, constructed and arranged to determine the orientation of a plane that includes the secondary coil with respect to the planes of the closest primary coils.

10. The electromagnetic field source of claim 9, wherein:

the orientation detector is electrically coupled to the plurality of primary coils and comprises a resonance frequency shift detector that compares shifts in inductance of two or more primary coils due to a proximity of the secondary coil.

11. The electromagnetic field source of claim 9, wherein:

the orientation detector comprises an optical sensor.

12. The electromagnetic field source of claim 9, wherein:

the orientation detector comprises an mechanical sensor.

13. The electromagnetic field source of claim 9, wherein:

the orientation detector comprises an electromagnetic transmission sensor.

14. The electromagnetic field source of claim 9, wherein:

the proximity detector, current director, and orientation detector are each implemented by at least one of a group of software, firmware, and electrical circuits.

15. The electromagnetic field source of claim 9, wherein:

when the orientation detector determines that the secondary coil is disposed in a plane predominantly parallel to the planes of the closest primary coils, the current director directs time-varying currents to flow through the closest primary coils so that each current flows in a same direction.

16. The electromagnetic field source of claim 15, wherein:

the quantity of closest primary coils is one when the proximity detector determines that the secondary coil is proximate to an electromagnetic field of the one closest primary coil, not including a dead zone.

17. The electromagnetic field source of claim 15, wherein:

the quantity of closest primary coils is two or more when all of the plurality of primary coils are disposed in a same plane and the proximity detector determines that the secondary coil is proximate to a dead zone of a one closest primary coil.

18. The electromagnetic field source of claim 9, wherein:

when the orientation detector determines that the secondary coil is disposed in a plane predominantly perpendicular to the planes of the closest primary coils, the current director directs time-varying currents to flow through the closest primary coils so that a current in each closest primary coil flows in a direction opposite to a direction of a current in an adjacent closest primary coil.

19. The electromagnetic field source of claim 18, wherein:

the quantity of closest primary coils is two.

20. The electromagnetic field source of claim 2, wherein:

the proximity detector is electrically coupled to the plurality of primary coils and identifies the quantity of closest primary coils utilizing a resonance frequency shift detector that detects a shift in inductance of one or more primary coils due to a proximity of the secondary coil.

21. The electromagnetic field source of claim 2, wherein:

the proximity detector identifies the quantity of closest primary coils utilizing an optical sensor.

22. The electromagnetic field source of claim 2, wherein:

the proximity detector identifies the quantity of closest primary coils utilizing a mechanical sensor.

23. The electromagnetic field source of claim 2, wherein:

the proximity detector identifies the quantity of closest primary coils utilizing electromagnetic transmission.

24. The electromagnetic field source of claim 2, wherein:

the proximity detector is further constructed and arranged to determine an approximate distance between one or more of the closet primary coils and the secondary coil, and

the current director is further constructed and arranged to increase the currents through the closest primary coils when the proximity detector determines that the distance is greater than a nominal threshold value.

25. The electromagnetic field source of claim 2, further comprising:

a power supply coupled to the current director and constructed and arranged to generate the current directed to the primary coils.

26. The electromagnetic field source of claim 1, further comprising:

one or more articles of furniture constructed and arranged to house the primary coils.

27. The electromagnetic field source of claim 26, wherein:

the furniture includes a bed.

28. The electromagnetic field source of claim 26, wherein:

the furniture includes at least one mattress having a top surface and the primary coils are positioned in the mattress.

29. The electromagnetic field source of claim 28, wherein:

the primary coils are disposed over substantially all of the top surface of the mattress.

30. The electromagnetic field source of claim 28, wherein:

the primary coils are positioned in generally even rows and columns with respect to the top surface of the mattress.

31. The electromagnetic field source of claim 28, wherein:

the primary coils are positioned in generally hexagonal arrangements with respect to the top surface of the mattress.

32. The electromagnetic field source of claim 1, further comprising:

a bed covering constructed and arranged to house the primary coils.

33. A method for providing electromagnetic energy to a secondary coil, comprising:

(1) providing an electromagnetic field source comprising a plurality of primary coils, each constructed and arranged to carry a time-varying current to produce an electromagnetic field, and a controller constructed and arranged to detect a position and orientation of the secondary coil relative to one or more of the plurality of primary coils and to selectively provide current to one or more of the plurality of primary coils based on the position and orientation of the secondary coil relative to the primary coils;

(2) detecting a position and orientation of one or more of the secondary coil relative to the plurality of primary coils by the controller; and

(3) selectively providing current to one or more of the plurality of primary coils based on the position and orientation of the secondary coil relative to the primary coils by the controller.

34. The method of claim 33, wherein:

the controller comprises a proximity detector and a current director responsive to the proximity detector and electrically coupled to the plurality of primary coils;

detecting a position in step 2 comprises identifying a quantity of the plurality of primary coils that are closest to the secondary coil by the proximity detector; and

selectively providing current in step 3 comprises selectively directing time-varying currents through the closest primary coils by the current director.

35. The method of claim 34, wherein:

the quantity of closest primary coils identified by the proximity detector is a predetermined value.

36. The method of claim 34, wherein:

the quantity of closest primary coils identified by the proximity detector is based on a size of the secondary coil.

37. The method of claim 34, wherein step 1 comprises:

providing each primary coil in a plane substantially parallel to, including the same plane as, a plane of each of the other primary coils.

38. The method of claim 37, wherein step 1 comprises providing the primary coils in two or more substantially parallel planes, including:

a first plane having one or more first-plane primary coils that, when energized, generate electromagnetic fields having one or more dead zones; and

a second plane having at least one second-plane primary coil positioned with respect to the two or more mutually adjacent first-plane primary coils to generate, when energized, at least one electromagnetic field encompassing the one or more dead zones.

39. The method of claim 37, wherein step 1 comprises providing the primary coils in two or more substantially parallel planes, including:

a first plane having two or more mutually adjacent first-plane primary coils; and

a second plane having at least one second-plane primary coil positioned with respect to the two or more mutually adjacent first-plane primary coils so that the projection of a magnetic center of the second-plane primary coil on the first plane is approximately equidistant from magnetic centers of each of the two or more mutually adjacent first-plane primary coils.

40. The method of claim 37, wherein step 1 comprises providing the primary coils in two or more substantially parallel planes, including:

a first plane having four mutually adjacent primary coils positioned with respect to each other in a roughly square arrangement; and

a second plane having one primary coil positioned so that the projection of its geometric center on the first plane is approximately centrally located among the four first plane primary coils.

41. The method of claim 34, wherein:

the controller further comprises an orientation director; and

detecting an orientation in step 2 further comprises determining the orientation of a plane that includes the secondary coil with respect to the planes of the closest primary coils by the orientation director.

42. The method of claim 41, wherein:

the orientation detector is electrically coupled to the plurality of primary coils and determines the orientation of the plane of the secondary coil utilizing a resonance frequency shift detector to compares shifts in inductance of two or more primary coils due to a proximity of the secondary coil.

43. The method of claim 41, wherein:

the orientation detector determines the plane of the secondary coil utilizing an optical sensor.

44. The method of claim 41, wherein:

the orientation detector determines the plane of the secondary coil utilizing a mechanical sensor.

45. The method of claim 41, wherein:

the orientation detector determines the plane of the secondary coil utilizing electromagnetic transmission.

46. The method of claim 41, wherein:

the proximity detector, current director, and orientation detector are each implemented by at least one of a group of software, firmware, and electrical circuits.

47. The method of claim 41, wherein:

when the orientation detector determines that the secondary coil is disposed in a plane predominantly parallel to the planes of the closest primary coils, the current director directs time-varying currents to flow through the closest primary coils so that each current flows in a same direction.

48. The method of claim 47, wherein:

the quantity of closest primary coils is one when the proximity detector determines that the secondary coil is proximate to an electromagnetic field of the one closest primary coil, not including a dead zone.

49. The method of claim 47, wherein:

the quantity of closest primary coils is two or more when all of the plurality of primary coils are disposed in a same plane and the proximity detector determines that the secondary coil is proximate to a dead zone of a one closest primary coil.

50. The method of claim 41, wherein:

when the orientation detector determines that the secondary coil is disposed in a plane predominantly perpendicular to the planes of the closest primary coils, the current director directs time-varying currents to flow through the closest primary coils so that a current in each closest primary coil flows in a direction opposite to a direction of a current in an adjacent closest primary coil.

51. The method of claim 50, wherein:

the quantity of closest primary coils is two.

52. The method of claim 43, wherein:

the proximity detector is electrically coupled to the plurality of primary coils and identifies the quantity of closest primary coils utilizing a resonance frequency shift detector that detects a shift in inductance of one or more primary coils due to a proximity of the secondary coil.

53. The method of claim 34, wherein:

the proximity detector identifies the quantity of closest primary coils utilizing an optical sensor.

54. The method of claim 34, wherein:

the proximity detector identifies the quantity of closest primary coils utilizing a mechanical sensor.

55. The method of claim 34, wherein:

the proximity detector identifies the quantity of closest primary coils utilizing electromagnetic transmission.

56. The method of claim 34, wherein:

the proximity detector is further constructed and arranged to determined an approximate distance between one or more of the closest primary coils and the secondary coil, and

the current director is further constructed and arranged to increase the currents through the closest primary coils when the proximity detector determines that the distance is greater than a nominal threshold value.

57. The method of claim 33, further comprising:

providing the primary coils in one or more articles of furniture.

58. The method of claim 57, wherein:

the furniture includes a bed.

59. The method of claim 57, wherein:

the furniture includes at least one mattress having a top surface and the primary coils are positioned in the mattress.

60. The method of claim 59, wherein:

the primary coils are disposed over substantially all of the top surface of the mattress.

61. The method of claim 59, wherein:

the primary coils are positioned in generally even rows and columns with respect to the top surface of the mattress.

62. The method of claim 59, wherein:

the primary coils are positioned in generally hexagonal arrangements with respect to the top surface of the mattress.

63. The method of claim 33, further comprising:

providing the primary coils in a bed covering.

64. A system for providing electromagnetic energy to a secondary coil, comprising:

a plurality of primary coils, each constructed and arranged to carry a time-varying current to produce an electromagnetic field; and

a controller means for detecting a position and orientation of the secondary coil relative to one or more of the plurality of primary coils and for selectively providing current to one or more of the plurality of primary coils based on the position and orientation of the secondary coil relative to the primary coils.

65. The system of claim 64, wherein the controller means comprises:

a proximity detector means for identifying a quantity of the plurality of primary coils that are closest to the secondary coil; and

a current director means, responsive to the proximity detector means and electrically coupled to the plurality of primary coils, for selectively directing time-varying currents through the closest primary coils.

66. The system of claim 65, wherein:

the quantity of closest primary coils identified by the proximity detector means is a predetermined value.

67. The system of claim 65, wherein:

the quantity of closest primary coils identified by the proximity detector means is based on a size of the secondary coil.

68. The system of claim 65, wherein:

each primary coil is disposed in a plane substantially parallel to, including the same plane as, a plane of each of the other primary coils.

69. The system of claim 68, wherein the primary coils are disposed in two or more substantially parallel planes, including:

a first plane having one or more first-plane primary coils that, when energized, generate electromagnetic fields having one or more dead zones; and

a second plane having at least one second-plane primary coil positioned with respect to the two or more mutually adjacent first-plane primary coils to generate, when energized, at least one electromagnetic field encompassing the one or more dead zones.

70. The system of claim 68, wherein the primary coils are disposed in two or more substantially parallel planes, including:

a first plane having two or more mutually adjacent first-plane primary coils; and

a second plane having at least one second-plane primary coil positioned with respect to the two or more mutually adjacent first-plane primary coils so that the projection of a magnetic center of the second-plane primary coil on the first plane is approximately equidistant from magnetic centers of each of the two or more mutually adjacent first-plane primary coils.

71. The system of claim 68, wherein the primary coils are disposed in two or more substantially parallel planes, including:

a first plane having four mutually adjacent primary coils positioned with respect to each other in a roughly square arrangement; and

a second plane having one primary coil positioned so that the projection of its geometric center on the first plane is approximately centrally located among the four first plane primary coils.

72. The system of claim 68, wherein the controller means comprises:

an orientation detector means, coupled to the current director means, for determining the orientation of a plane that includes the secondary coil with respect to the planes of the closest primary coils.

73. The system of claim 72, wherein:

the orientation detector means is electrically coupled to the plurality of primary coils and comprises a resonance frequency shift detector means for determining the orientation of the plane of the secondary coil by comparing shifts in inductance of two or more primary coils due to a proximity of the secondary coil.

74. The system of claim 72, wherein:

the orientation detector means comprises an optical sensor means for determining the plane of the secondary coil utilizing an optical sensor.

75. The system of claim 72, wherein:

the orientation detector means comprises a mechanical sensor means for determining the plane of the secondary coil.

76. The system of claim 72, wherein:

the orientation detector means comprises an electromagnetic transmission detector means for determining the plane of the secondary coil.

77. The system of claim 76, wherein:

the primary coils are positioned in generally hexagonal arrangements with respect to the top surface of the mattress.

78. The system of claim 72, wherein:

the proximity detector means, current director means, and orientation detector means are each implemented by at least one of a group of software, firmware, and electrical circuits.

79. The system of claim 72, wherein:

when the orientation detector means determines that the secondary coil is disposed in a plane predominantly parallel to the planes of the closest primary coils, the current director means directs time-varying currents to flow through the closest primary coils so that each current flows in a same direction.

80. The system of claim 79, wherein:

the quantity of closest primary coils is one when the proximity detector means determines that the secondary coil is proximate to an electromagnetic field of the one closest primary coil, not including a dead zone.

81. The system of claim 79, wherein:

the quantity of closest primary coils is two or more when all of the plurality of primary coils are disposed in a same plane and the proximity detector means determines that the secondary coil is proximate to a dead zone of a one closest primary coil.

82. The system of claim 72, wherein:

when the orientation detector means determines that the secondary coil is disposed in a plane predominantly perpendicular to the planes of the closest primary coils, the current director means directs time-varying currents to flow through the closest primary coils so that a current in each closest primary coil flows in a direction opposite to a direction of a current in an adjacent closest primary coil.

83. The system of claim 82, wherein:

the quantity of closest primary coils is two.

84. The system of claim 65, wherein:

the proximity detector means is electrically coupled to the plurality of primary coils and comprises a resonance frequency shift detector means for identifying the quantity of closest primary coils by detecting a shift in inductance of one or more primary coils due to a proximity of the secondary coil.

85. The system of claim 65, wherein:

the proximity detector means comprises an optical sensor means for identifying the quantity of closest primary coils.

86. The system of claim 65, wherein:

the proximity detector means comprises a mechanical sensor means for identifying the quantity of closest primary coils.

87. The system of claim 65, wherein:

the proximity detector means comprises an electromagnetic transmission detector means for identifying the quantity of closest primary coils.

88. The system of claim 65, wherein:

the proximity detector means is further constructed and arranged to determine an approximate distance between one or more of the closest primary coils and the secondary coil, and

the current director means is further constructed and arranged to increase the currents through the closest primary coils when the proximity detector determines that the distance is greater than a nominal threshold value.

89. The system of claim 65, wherein the current director means includes a power adjuster means for adjusting the amount of current directed to the closest primary coils.

90. The system of claim 65, wherein the current director means includes a current direction determiner means for determining the directions of current supplied to two or more closest primary coils.

91. The system of claim 65, wherein the current director means includes a primary coil selector means for selecting primary coils to receive the current.

92. The system of claim 64, further comprising:

a power supply coupled to the current director means.

93. The system of claim 64, further comprising:

one or more articles of furniture constructed and arranged to house the primary coils.

94. The system of claim 93, wherein:

the furniture includes a bed.

95. The system of claim 93, wherein:

the furniture includes at least one mattress having a top surface and the primary coils are positioned in the mattress.

96. The system of claim 95, wherein:

the primary coils are disposed over substantially all of the top surface of the mattress.

97. The system of claim 95, wherein:

the primary coils are positioned in generally even rows and columns with respect to the top surface of the mattress.

98. The system of claim 64, further comprising:

a bed covering constructed and arranged to house the primary coils.