System and method for controlling current provided to a stepping motor

• US 20050206340A1
• Filed: 03/17/2004
• Published: 09/22/2005
• Est. Priority Date: 03/17/2004
• Status: Active Grant

• Current Assignee: Baxter International Inc.
• Original Assignee: Baxter International Inc.
• Inventors: Dao, Son, Allen, Tim, Brundle, Alan
• Granted Patent: US 7,338,260 B2
• Time in Patent Office: Days
• US Class Current: 318/685
• CPC Class Codes: A61M 2205/3351 Controlling upstream pump pressure
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2205/8212 with means or measures taken for minimising energy consumption
• CPC Class Codes: A61M 5/142 Pressure infusion, e.g. using pumps
• CPC Class Codes: A61M 5/14216 Reciprocating piston type
• CPC Class Codes: A61M 5/14228 with linear peristaltic action, i.e. comprising at least three pressurising members or a helical member
• CPC Class Codes: G05B 2219/41206 Lookup table, memory with certain relationships
• CPC Class Codes: G05B 2219/41326 Step motor

Abstract

A system and method is disclosed for controlling the input electrical current to an infusion pump stepper motor based on predetermined torque requirements. The system can include a motor controller and a non-volatile memory containing expected load torque values throughout a pump cycle. Responsive to the expected load torque values, the motor controller provides the stepper motor with a varying electrical current for overcoming load torque at each point in the pumping cycle. Additional factors can also be considered for varying the electrical current. These factors include, but are not limited to, temperature, pressure, and elapsed operating time.

Claims

1. A method for driving an infusion pump motor, comprising the steps of:

determining a position in a pump cycle; and

determining the electrical current value for driving the infusion pump stepper motor in response, at least in part, to the position in the pump cycle.

2. The method of claim 1, wherein the position in the pump cycle and the electrical current value are related to each other in a relationship in a database.

3. The method of claim 1, further comprising the step of determining a flow rate, wherein the electrical current value is related to the position in the pump cycle and the flow rate.

4. The method of claim 3, wherein the position in the pump cycle, the flow rate and the current value are stored in a database, and wherein the position in the pump cycle and the flow rate are related to the electrical current value.

5. The method of claim 3, further comprising the step of modifying the electrical current value in response to temperature information.

6. The method of claim 3, further comprising the step of modifying the electrical current value in response to distal pressure information.

7. The method of claim 3, further comprising the step of modifying the electrical current value in response to an elapsed time value.

8. The method of claim 3, further comprising the step of modifying the electrical current value in response to the age of the infusion pump motor.

9. The method of claim 1, further comprising the step of half-stepping the infusion pump motor.

10. The method of claim 1, further comprising the step of microstepping the infusion pump motor.

11. A system comprising:

a sensor having an output;

a motor controller having an output responsive to the sensor output;

a current driver having an electrical current output responsive to the motor controller output;

a stepper motor responsive to the electrical current output.

12. The system of claim 11 wherein the stepper motor is contained within an infusion pump.

13. The system of claim 12 wherein the infusion pump provides for operation under battery power.

14. The system of claim 11 wherein the output of the sensor is responsive to temperature changes.

15. The system of claim 11 wherein the output of the sensor is responsive to backpressure changes.

16. The system of claim 11 wherein the output of the sensor is responsive to changes in the position of the stepper motor.

17. The system of claim 11 wherein the output of the motor controller is responsive to changes in the age of tubing used for administering medication.

18. The system of claim 11 wherein the output of the motor controller is responsive to changes in the age of the stepper motor.

19. The system of claim 11 further comprising a memory containing data wherein the electrical current output is responsive to the data and the sensor output.

20. The system of claim 19 wherein the controller and memory are within a microcontroller.

21. The system of claim 19 wherein the output of the sensor is responsive to temperature changes.

22. The system of claim 19 wherein the output of the sensor is responsive to backpressure changes.

23. The system of claim 19 wherein the output of the sensor is responsive to changes in the position of the stepper motor.

24. The system of claim 11 further comprising one or more additional sensors having outputs, wherein the output of the motor controller is responsive to the sensor outputs, and wherein the output of at least one of the sensors is responsive to the position of the stepper motor.

25. A system comprising:

a sensor having an output;

a motor controller having an output responsive to the sensor output;

a current driver having an electrical current output responsive to the motor controller output;

a stepper motor responsive to the electrical current output, the stepper motor contained within an infusion pump providing for operation under battery power.

26. The system of claim 25 wherein the output of the sensor is responsive to temperature changes.

27. The system of claim 25 wherein the output of the sensor is responsive to backpressure changes.

28. The system of claim 25 wherein the output of the sensor is responsive to changes in the position of the stepper motor.

29. The system of claim 25 wherein the output of the motor controller is responsive to changes in the age of tubing used for administering medication.

30. The system of claim 25 wherein the output of the motor controller is responsive to changes in the age of the stepper motor.

31. The system of claim 25 further comprising a memory containing data wherein the electrical current output is responsive to the data and the sensor output.

32. The system of claim 31 wherein the output of the sensor is responsive to temperature changes.

33. The system of claim 31 wherein the output of the sensor is responsive to backpressure changes.

34. The system of claim 31 wherein the output of the sensor is responsive to changes in the position of the stepper motor.