Artificial heart with sensorless motor

• US 5,751,125 A
• Filed: 11/08/1995
• Issued: 05/12/1998
• Est. Priority Date: 11/08/1995
• Status: Expired due to Term

• Current Assignee: Penn State Research Foundation (Pennsylvania State University)
• Original Assignee: Penn State Research Foundation (Pennsylvania State University)
• Inventors: Weiss, William J.
• Primary Examiner(s): Masih, Karen
• Application Number:
  US08/555,161
• Time in Patent Office: 916 Days
• Field of Search: 318/280, 318/290, 318/254, 318/439, 318/138
• US Class Current: 318/280
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 60/148 in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/196 replacing the entire heart, e.g. total artificial hearts [TAH]
• CPC Class Codes: A61M 60/446 the axis of both movements being parallel, e.g. roller screw actuators or cylindrical cam transmissions
• CPC Class Codes: A61M 60/538 Regulation using real-time blood pump operational parameter data, e.g. motor current
• CPC Class Codes: A61M 60/894 Passive valves, i.e. valves actuated by the blood
• CPC Class Codes: F04B 43/026 each plate-like pumping flexible member working in its own pumping chamber
• CPC Class Codes: F04B 43/04 Pumps having electric drive
• CPC Class Codes: H02K 21/16 having annular armature cores with salient poles with homopolar co-operation H02K21/20
• CPC Class Codes: H02K 7/06 Means for converting reciprocating motion into rotary motion or vice versa
• CPC Class Codes: H02P 6/085 in a bridge configuration
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/30 Arrangements for controlling the direction of rotation H02P6/22 takes precedence

Abstract

An artificial heart assembly, designed for implantation into a subject, which may be a total artificial heart or a ventricular assist device. The artificial heart assembly has a blood inlet conduit, a blood outlet conduit, a pumping mechanism for pumping blood from the blood inlet conduit to the blood outlet conduit, and a sensorless, DC brushless motor operatively connected to the pumping mechanism. The motor is reversibly driven in a first direction and a second direction, the motor changing between the first and second directions at a rate of at least 30 times per minute. The artificial heart assembly has means for periodically applying electrical signals to a plurality of the motor terminals while leaving at least one of the motor terminals unenergized, means for detecting a voltage at the unenergized motor terminal, and means for determining, based upon the voltage at the unenergized terminal, the angular position of the rotor with respect to the stator.

Claims

1. An artificial heart assembly having a sensorless, DC brushless motor, said artificial heart assembly comprising:

a blood inlet conduit;

a blood outlet conduit;

a pumping mechanism for pumping blood from said blood inlet conduit to said blood outlet conduit;

a sensorless, DC brushless motor operatively connected to said pumping mechanism, said motor being reversibly driven in a first direction and a second direction, said motor changing between said first and second directions at a rate of at least 30 times per minute, said motor comprising;

a permanent magnet rotor; and

a stator rotatable relative to said permanent magnet rotor, said stator having a plurality of electrically energizable windings and a plurality of motor terminals to which said windings are electrically connected, wherein said rotor may be in Y possible angular position sectors with respect to said stator and wherein Y has a numeric value greater than two;

means for periodically applying electrical signals to a plurality of said motor terminals while leaving at least one of said motor terminals unenergized to cause said rotor to rotate alternately in said first direction and second directions, said rotor changing between said first and second directions at a rate of at least about 30 times per minute;

means for detecting a voltage at said unenergized motor terminal; and

means for determining, based upon said voltage detected by said detecting means, that said rotor is in one of X possible angular position sectors, where X has a numeric value less than said numeric value of Y.

2. An artificial heart assembly as defined in claim 1 wherein X has a numeric value not greater than two.

3. An artificial heart assembly as defined in claim 2 wherein Y has a numeric value of at least six.

4. An artificial heart assembly as defined in claim 1 wherein said windings comprise delta-connected windings.

5. An artificial heart assembly as defined in claim 1 wherein said detecting means detects said voltage on said unenergized motor terminal while said rotor is stationary with respect to said stator.

6. An artificial heart assembly as defined in claim 1 wherein said means for applying electrical signals to said motor terminals comprises means for determining when a new set of electrical signals should be applied to said windings, based upon the detection of said voltage at said unenergized motor terminal, in order to move said rotor from a first of said angular position sectors to a second one of said angular position sectors.

7. An artificial heart assembly as defined in claim 1 wherein said means for determining that said rotor is in one of X possible angular position sectors comprises means for determining an inductance ratio based on said voltage on said unenergized terminal.

8. An artificial heart assembly as defined in claim 1 wherein said means for determining that said rotor is in one of X possible angular position sectors comprises means for determining an inductance ratio based on said voltage on said unenergized terminal and comparing said inductance ratio with a threshold value.

9. An artificial heart assembly as defined in claim 1 wherein said means for applying electrical signals to said motor terminals comprises means for applying a voltage across a first pair of said motor terminals during a first period of time while leaving a first motor terminal unenergized, for applying a voltage across a second pair of said motor terminals during a second period of time while leaving a second motor terminal unenergized, and for applying a voltage across a third pair of said motor terminals during a third period of time while leaving a third motor terminal unenergized, and wherein said detecting means comprises means for detecting a first voltage on said first unenergized motor terminal during said first period of time, for detecting a second voltage on said second unenergized motor terminal during said second period of time, and for detecting a third voltage on said third unenergized motor terminal during said third period of time.

10. An artificial heart assembly as defined in claim 9 wherein said means for determining that said rotor is in one of X possible angular position sectors comprises means for determining an inductance ratio based on each of said first, second and third voltages on said unenergized terminals.

11. An artificial heart assembly as defined in claim 9 wherein said means for determining that said rotor is in one of X possible angular position sectors comprises:

means for determining a first inductance ratio based on one of said first, second and third voltages on said unenergized terminals and a second inductance ratio based on another of said first, second and third voltages on said unenergized terminals; and

means for comparing said first inductance ratio with a threshold value to determine whether said first inductance ratio is greater than said threshold value and for comparing said second inductance ratio with said threshold value to determine whether said second inductance ratio is less than said threshold value.

12. An artificial heart assembly as defined in claim 1 wherein said determining means determines which of said angular position sectors said rotor is in.

13. An artificial heart assembly as defined in claim 1 additionally comprising a membrane defining a blood chamber fluidly coupled to said blood inlet conduit and said blood outlet conduit, wherein said pumping mechanism comprises a pusher plate which makes contact with said membrane to force blood from said blood inlet conduit to said blood outlet conduit.

14. An artificial heart assembly as defined in claim 1 additionally comprising:

a first membrane defining a blood chamber fluidly coupled to said blood inlet conduit and said blood outlet conduit, wherein said pumping mechanism comprises a pusher plate which makes contact with said first membrane to force blood from said blood inlet conduit to said blood outlet conduit;

a second membrane defining a second blood chamber fluidly coupled to a second blood inlet conduit and a second blood outlet conduit; and

a second pusher plate which makes contact with said second membrane to force blood from said second blood inlet conduit to said second blood outlet conduit.

15. An artificial heart assembly having a sensorless, DC brushless motor, said artificial heart assembly comprising:

a blood inlet conduit;

a blood outlet conduit;

a pumping mechanism for pumping blood from said blood inlet conduit to said blood outlet conduit;

a sensorless, DC brushless motor coupled to said pumping mechanism, said motor comprising;

a permanent magnet rotor; and

a stator rotatable relative to said permanent magnet rotor, said stator having a plurality of electrically energizable windings and a plurality of motor terminals to which said windings are electrically connected, said rotor being movable from a first angular position sector relative to said stator to a second angular position sector relative to said startor;

means for periodically applying electrical signals to a plurality of said motor terminals while leaving at least one of said motor terminals unenergized to produce on said unenergized motor terminal a periodic signal which undergoes a least three cycles while said rotor is one of said angular position sectors and which has a plurality of relatively high voltage portions V_H alternated with a plurality of relatively low voltage portions V_L ;

and means for determining when a new set of electrical signals should be applied to said windings, based upon detection of the magnitude of at least one of said voltage portions of said periodic signal on said unenurgized motor terminal, in order to move said rotor from said first angular position sector to said second angular position sector.

16. An artificial heart assembly as defined in claim 15 wherein said means for applying electrical signals applies a pulse-width modulated signal to at least one of said motor terminals and wherein said means for determining when a new set of electrical signals should be applied to said windings comprises means for determining when one of said voltage portions V_L reaches a threshold value.

17. An artificial heart assembly as defined in claim 15 wherein said means for applying electrical signals applies a pulse-width modulated signal to at least one of said motor terminals, additionally comprising means for calculating a voltage difference Δ

V between one of said voltage portions V_H and one of said voltage portions V_L, and wherein said determining means determines when a new set of electrical signals should be applied to said windings based upon said voltage difference Δ

V.

18. An artificial heart assembly as defined in claim 15 wherein said means for applying electrical signals applies a pulse-width modulated signal to at least one of said motor terminals, additionally comprising means for calculating a voltage difference Δ

V between one of said voltage portions V_H and one of said voltage portions V_L, and wherein said means for determining when a new set of electrical signals should be applied to said windings comprises means for determining when said voltage difference Δ

V reaches a threshold value.

19. An artificial heart assembly as defined in claim 15 wherein said rotor may be in Y possible angular position sectors with respect to said stator and wherein Y has a numeric value greater than two, additionally comprising means for determining, based upon said voltage detected by said detecting means, that said rotor is in one of X possible positions, where X has a numeric value less than said numeric value of Y.

20. An artificial heart assembly as defined in claim 15 additionally comprising means for keeping track of the current position of the pumping mechanism.

21. An artificial heart assembly as defined in claim 15 wherein said windings comprise delta-connected windings.

22. An artificial heart assembly as defined in claim 15 additionally comprising a membrane defining a blood chamber fluidly coupled to said blood inlet conduit and said blood outlet conduit, wherein said pumping mechanism comprises a pusher plate which makes contact with said membrane to force blood from said blood inlet conduit to said blood outlet conduit.

23. An apparatus as defined in claim 15 wherein said means for periodically applying electrical signals to said motor terminals comprises means for causing said rotor to change between first and second alternating directions at a rate of at least about 30 times per minute.

24. An artificial heart assembly having a sensorless, DC brushless motor, said artificial heart assembly comprising:

a blood inlet conduit;

a blood outlet conduit;

a pumping mechanism for pumping blood from said blood inlet conduit to said blood outlet conduit;

a sensorless, DC brushless motor coupled to said pumping mechanism, said motor comprising;

a permanent magnet rotor; and

a stator rotatable relative to said permanent magnet rotor, said stator having a plurality of electrically energiziable windings and a plurality of motor terminals to which said windings are electrically connected, said rotor being movable from a first angular position sector relative to said stator to a second angular position sector relative to said stator;

means for periodically applying electrical signals to a plurality of said motor terminals while leaving at least one of said motor terminals unenergized to cause said rotor to rotate alternately in said first direction and second directions, said rotor changing between said first and second directions at a rate of at least about 30 times per minute;

means for periodically detecting a voltage at said unenergized motor terminal; and

means for determining when a new set of electrical signals should be applied to said windings, based upon the detection of said voltage at said unenergized motor terminal, in order to move said rotor from said first angular position sector to said second angular position sector,

wherein said means for applying electrical signals applies a pulse-width modulated signal to at least one of said motor terminals, wherein said voltage at said unenergized motor terminal has a plurality of relatively high voltage portions V_H alternated with a plurality of relatively low voltage portions V_L, and wherein said determining means determines when a new set of electrical signals should be applied to said windings based upon one of said voltage portions V_L.

25. An artificial heart assembly having a sensorless, DC brushless motor, said artificial heart assembly comprising:

a blood inlet conduit;

a blood outlet conduit;

a pumping mechanism for pumping blood from said blood inlet conduit to said blood outlet conduit; and

a sensorless, DC brushless motor coupled to said pumping mechanism, said motor comprising;

a permanent magnet rotor; and

a stator rotatable relative to said permanent magnet rotor, said stator having a plurality of electrically energiziable windings and a plurality of motor terminals to which said windings are electrically connected said rotor being movable from a first angular position sector relative to said stator to a second angular position sector relative to said stator;

means for periodically applying electrical signals to a plurality of said motor terminals while leaving at least one of said motor terminals unenergized to cause said rotor to rotate alternately in said first direction and second directions, said rotor changing between said first and second directions at a rate of at least about 30 times per minute;

means for periodically detecting a voltage at said unenergized motor terminal;

means for determining when a new set of electrical signals should be applied to said windings, based upon the detection of said voltage at said unenergized motor terminal, in order to move said rotor from said first angular position sector to said second angular position sector; and

means for keeping track of the current angular position sector occupied by the rotor.

26. An artificial heart assembly having a sensorless, DC brushless motor, said artificial heart assembly comprising:

a blood inlet conduit;

a blood outlet conduit;

a pumping mechanism for pumping blood from said blood inlet conduit to said blood outlet conduit;

a sensorless, DC brushless motor coupled to said pumping mechanism, said motor comprising;

a permanent magnet rotor; and

a stator rotatable relative to said permanent magnet rotor, said stator having a plurality of electrically energizable windings and a plurality of motor terminals to which said windings are electrically connected, said rotor being movable from a first angular position sector relative to said stator to a second angular position sector relative to said stator;

means for periodically applying electrical signals to a plurality of said motor terminals while leaving at least one of said motor terminals unenergized to cause said rotor to rotate alternately in said first direction and second directions, said rotor changing between said first and second directions at a rate of at least about 30 times per minute;

means for periodically detecting a voltage at said unenergized motor terminal;

means for determining when a new set of electrical signals should be applied to said windings, based upon the detection of said voltage at said unenergized motor terminal, in order to move said rotor from said first angular position sector to said second angular position sector;

a first membrane defining a blood chamber fluidly coupled to said blood inlet conduit and said blood outlet conduit, wherein said pumping mechanism comprises a pusher plate which makes contact with said first membrane to force blood from said blood inlet conduit to said blood outlet conduit;

a second membrane defining a second blood chamber fluidly coupled to a second blood inlet conduit and a second blood outlet conduit; and

a second pusher plate which makes contact with said second membrane to force blood from said second blood inlet conduit to said second blood outlet conduit.

27. A method of operating an artificial heart assembly having a blood inlet conduit, a blood outlet conduit, a pumping mechanism for pumping blood from the blood inlet conduit to the blood outlet conduit, and a sensorless DC brushless motor coupled to the pumping mechanism and having a permanent magnet rotor, a stator rotatable relative to the rotor and having a plurality of electrically energizable windings and a plurality of motor terminals to which the windings are electrically connected, the rotor being movable from a first angular position sector relative to the stator to a second angular position sector relative to the stator, said method comprising the steps of:

(a) periodically applying electrical signals to a plurality of the motor terminals while the rotor is moving relative to the stator and while leaving at least one of the motor terminals unenergized to produce on said unenergized motor terminal a periodic signal which undergoes at least three cycles while said rotor is in one of said angular position sectors and which has a plurality of relatively high voltage portions alternated with a plurality of relatively low voltage portions; and

(b) determining when a new set of electrical signals should be applied to the windings, based upon one of said voltage portions of said periodic signal on the unenergized motor terminal, in order to move the rotor from the first angular position sector to the second angular position sector.

28. A method as defined in claim 27 wherein said step (a) comprises the step of periodically applying electrical signals to a plurality of the motor terminals while the rotor is moving relative to the stator to cause the rotor to rotate alternately in the first direction and second directions at a rate of at least about 30 times per minute.

29. A method as defined in claim 27 wherein said step (a) comprises the step of applying a pulse-width modulated signal to at least one of the motor terminals, said method additionally comprising the steps of:

(c1) detecting a plurality of relatively high voltage portions V_H on the unenergized motor terminal; and

(c2) detecting a plurality of relatively low voltage portions V_L on the unenergized motor terminal.

30. A method as defined in claim 29 wherein said step (b) comprises the step of determining when a new set of electrical signals should be applied to the windings based upon the magnitude of one of the voltage portions V_L.

31. A method as defined in claim 29 wherein said step (b) comprises the step of determining when a new set of electrical signals should be applied to the windings based upon when one of the voltage portions V_L reaches a threshold value.

32. A method as defined in claim 29 additionally comprising the step of calculating a voltage difference Δ

V between one of the voltage portions V_H and one of the voltage portions V_L.

33. A method as defined in claim 32 wherein said step (b) comprises the step of determining when a new set of electrical signals should be applied to the windings based upon the voltage difference Δ

V.

34. A method as defined in claim 32 wherein said step (b) comprises the step of determining when a new set of electrical signals should be applied to the windings by determining when the voltage difference Δ

V reaches a threshold value.

35. A method as defined in claim 27 additionally comprising the step of keeping track of the current angular position sector occupied by the rotor.

36. A method as defined in claim 27 additionally comprising the step of keeping track of the current position of the pumping mechanism.

37. An artificial heart assembly having a sensorless, DC brushless motor, said artificial heart assembly comprising:

a blood inlet conduit;

a blood outlet conduit;

a pumping mechanism for pumping blood from said blood inlet conduit to said blood outlet conduit;

a sensorless, DC brushless motor coupled to said pumping mechanism, said motor comprising;

a permanent magnet rotor; and

a stator rotatable relative to said permanent magnet rotor, said stator having a plurality of electrically energizable windings and a plurality of motor terminals to which said windings are electrically connected, said rotor being movable from a first angular position sector relative to said stator to a second angular position sector relative to said stator;

means for periodically applying, while said rotor is stationary, electrical signals to a plurality of said motor terminals while leaving at least one of said motor terminals unenergized, at least one of said electrical signals comprising a periodic signal;

means for detecting a voltage at said unenergized motor terminal, said voltage at said unenergized motor terminal having a plurality of relatively high voltage portions V_H alternated with a plurality of relatively low voltage portions V_L ; and

means for determining the position of said rotor, while said rotor is stationary, based upon detection of one of said voltage portions at said unenergized motor terminal.