End of stroke detection for electromagnetic pump

• US 8,657,587 B2
• Filed: 07/26/2011
• Issued: 02/25/2014
• Est. Priority Date: 05/22/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Sarkinen, Scott A., Haase, James M., Mezera, Ronald L., Peclat, Christian Michel
• Primary Examiner(s): Freay, Charles
• Assistant Examiner(s): COMLEY, ALEXANDER BRYANT
• Application Number:
  US13/190,769
• Publication Number:
  US 20110280737A1
• Time in Patent Office: 945 Days
• Field of Search: 417/44.1, 417/44.11, 324/207.11, 324/207.16, 324/207.14
• 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 may be performed using, for example, a calculated first flux derivative. Further, inductance of a coil that can be energized to produce a pump stroke may be calculated (e.g., the pump may include an actuator moveable in response to the energization of the coil). For example, the inductance may be calculated as a function of sense coil current and source electrical potential when the actuator is not moving for use in determining position of the actuator.

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 calculate inductance of the coil as a function of sensed coil current and source electrical potential when the actuator is not moving for use in determining position of the actuator, 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, where U_source is source electrical potential, R_coil is the resistance of the coil, R_source is the resistance of the source, and I_coil is the coil current.

2. The system of claim 1, wherein the control electronics calculates inductance after detection of end of stroke and prior to end of current in the coil.

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

4. A method for use in controlling an electromagnetic pump, the electromagnetic pump comprising a coil that can be energized by a power source to produce a pump stroke and an actuator moveable in response to the energization of the coil, wherein the method comprises:

applying, using a direct current power source, a source electrical potential to the coil to pass a coil current therethrough to provide a pump stroke;

sensing the source electrical potential applied to the coil;

sensing the coil current; and

detecting the end of the 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.

5. The method of claim 4, wherein detecting the end of the pump stroke comprises calculating 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.

6. The method of claim 5, wherein detecting the end of the pump stroke comprises performing 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.

7. The method of claim 5, wherein detecting the end of the pump stroke comprises performing trough detection to detect a minimum in U_source−

(R_coil*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.

8. The method of claim 5, wherein detecting the end of the pump stroke comprises performing peak detection to detect a peak in I_coil as sensed 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.

9. The method of claim 4, wherein selectively applying a source electrical potential to the coil comprises connecting the power source to the coil at the initiation of a pump stroke and disconnecting the power source from the coil upon detection of an end of the pump stroke.

10. The method of claim 4, wherein the method further comprises calculating inductance of the coil as a function of sensed coil current and source electrical potential to verify position of the actuator.

11. The method of claim 10, wherein calculating inductance comprises calculating (U_source−

(R_coil+R_source)*I_coil)/d/dt I_coil, where U_source is source electrical potential, R_coil is the resistance of the coil, R_source is the resistance of the source, and I_coil is the coil current.

12. The method of claim 10, wherein the method further comprises calculating inductance after detection of end of stroke and prior to end of current in the coil.

13. The method of claim 4, wherein the pump stroke delivers infusion medium.

14. A method for use in controlling an electromagnetic pump, the electromagnetic pump comprising a coil that can be energized by a power source to produce a pump stroke and an actuator moveable in response to the energization of the coil, wherein the method comprises:

applying, using a direct current power source, a source electrical potential to the coil to pass a coil current therethrough to provide a pump stroke;

sensing the source electrical potential applied to the coil;

sensing the coil current; and

calculating inductance of the coil as a function of sensed coil current and source electrical potential for use in determining position of the actuator, wherein calculating inductance comprises calculating (U_source−

(R_coil+R_source)*I_coil)/d/dt I_coil, where U_source is source electrical potential, R_coil is the resistance of the coil, R_source is the resistance of the source, and I_coil is the coil current.

15. The method of claim 14, wherein the method further comprises calculating inductance after detection of end of pump stroke and prior to end of current in the coil.