End of stroke detection for electromagnetic pump

• US 8,007,247 B2
• Filed: 05/22/2007
• Issued: 08/30/2011
• Est. Priority Date: 05/22/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Peclat, Christian Michel, Mezera, Ronald L., Sarkinen, Scott A., Haase, James M.
• Primary Examiner(s): Freay; Charles
• Assistant Examiner(s): COMLEY, ALEXANDER BRYANT
• Application Number:
  US11/805,124
• Publication Number:
  US 20080294098A1
• Time in Patent Office: 1,561 Days
• Field of Search: 417/44.1, 417/53, 417/505, 417/212, 417/44.11, 417/415, 604/67, 604/891.1, 604/151, 604/152, 324/207.24
• US Class Current: 417/44.11
• CPC Class Codes: A61M 2205/8212 with means or measures taken for minimising energy consumption
• CPC Class Codes: A61M 5/14216 Reciprocating piston type
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: F04B 17/048 the fluid flowing around the moving part of the motor
• CPC Class Codes: F04B 2201/0201 Position of the piston
• CPC Class Codes: F04B 2203/0401 Current
• CPC Class Codes: F04B 2203/0402 Voltage
• CPC Class Codes: F04B 2203/0403 Magnetic flux
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04

Abstract

Detection of end of stroke for an electromagnetic pump is performed using, for example, a calculated first flux derivative.

Claims

1. An electromagnetic pump system comprising:

an electromagnetic pump comprising a coil that can be energized to produce a pump stroke, wherein the electromagnetic pump further comprises an actuator moveable in response to the energization of the coil;

a direct current power source connected to selectively energize the coil of the electromagnetic pump, wherein the power source applies a source electrical potential to the coil to pass a coil current therethrough;

a voltage sense device for sensing the source electrical potential applied to the coil;

a current sense device for sensing the coil current; and

control electronics to detect the end of a pump stroke based on a change in flux over time calculated as a function of sensed coil current and source electrical potential, wherein the change in flux over time is calculated independent of coil inductance L_coil.

2. The system of claim 1, wherein the control electronics calculates U_source−

(R_coil*I_coil) over time corresponding to the change of flux over time, where U_source is source electrical potential, R_coil is the resistance of the coil, and I_coil is the coil current.

3. The system of claim 1, wherein the control electronics performs peak detection to detect a peak in U_source−

(R_coil*I_coil) as calculated over time corresponding to the end of a pump stroke.

4. The system of claim 3, wherein the control electronics performs trough detection to detect a minimum in U_source−

(R_coii*I_coil) as calculated over time prior to performing peak detection to detect a peak in U_source−

(R_coil*I_coil) corresponding to the end of a pump stroke.

5. The system of claim 3, wherein the control electronics performs peak detection to detect a peak in I_coil as provided over time prior to performing peak detection to detect a peak in U_source−

(R_coil*I_coil) corresponding to the end of a pump stroke.

6. The system of claim 1, wherein the control electronics comprises a switch device connected between the power source and the coil to connect the power source to the coil at the initiation of a pump stroke and disconnect the power source from the coil upon detection of an end of the pump stroke.

7. The system of claim 1, wherein the control electronics further calculates inductance of the coil as a function of sensed coil current and source electrical potential when the actuator is not moving.

8. The system of claim 7, wherein the control electronics calculates (U_source−

(R_coil+R_source)*I_coil)/d/dt I_coil for use in determining position of the actuator.

9. The system of claim 7, wherein the control electronics calculates inductance after detection of end of stroke and prior to end of current in the coil.

10. The system of claim 1, wherein the system is part of an implantable medical device.

11. An implantable infusion device for delivery of infusion medium, the infusion device comprising:

a drive mechanism comprising a coil that can be energized to produce a pump stroke, wherein the drive mechanism further comprises an actuator moveable relative to the coil in response to the energization of the coil to deliver infusion medium;

a direct current power source connected to selectively energize the coil of the electromagnetic pump, wherein the power source applies a source electrical potential to the coil to pass a coil current therethrough;

one or more sense devices to sense the source electrical potential applied to the coil and to sense the coil current; and

control electronics to detect the end of a pump stroke based on a change in flux over time calculated as a function of sensed coil current and source electrical potential, wherein the change in flux over time is calculated independent of coil inductance L_coil, and wherein the control electronics further comprises a switch device connected between the power source and the coil to connect the power source to the coil at the initiation of a pump stroke and disconnect the power source from the coil upon detection of an end of the pump stroke.

12. The device of claim 11, wherein the control electronics calculates U_source−

(R_coil*I_coil) over time corresponding to the change of flux over time, where U_source is source electrical potential, R_coil is the resistance of the coil, and I_coil is the coil current.

13. The device of claim 11, wherein the control electronics performs peak detection to detect a peak in U_source−

(R_coil*I_coil) as calculated over time corresponding to the end of a pump stroke.

14. The device of claim 11, wherein the power source comprises a capacitor connected to receive a charge from a battery and is connectable to the coil by the switch device to selectively discharge power to the coil.

15. The device of claim 11, wherein the control electronics further calculates inductance of the coil as a function of sensed coil current and source electrical potential when the actuator is not moving.

16. The device of claim 15, wherein the control electronics calculates inductance after detection of end of a pump stroke and prior to end of current in the coil.