Motor health monitoring and medical device incorporating same

Patent metadata

Field	Value
Publication number	US-9379652-B2
Application number	US-201313945737-A
Country	US
Kind code	B2
Filing date	Jul 18, 2013
Priority date	Mar 20, 2012
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

Apparatus are provided for motor control systems and related medical devices. In one embodiment, a control system includes a motor having a rotor, a modulation module coupled to the motor, and a control module coupled to the motor and the modulation module. The modulation module generates a modulated voltage that is applied to the motor, and the control module adjusts a duty cycle of the modulated voltage to achieve a commanded rotation of the rotor and detects a degradation condition based on the duty cycle.

First claim

What is claimed is:

1. A system comprising:
a stepper motor having a rotor and sets of windings;
a sensor to detect incremental rotations of the rotor;
a modulation module to generate a modulated voltage oscillating between a first voltage and a second voltage, the modulated voltage being equal to the first voltage for a percentage of a time interval, the percentage corresponding to a duty cycle;
a motor driver module coupled between the modulation module and the stepper motor to apply the modulated voltage to one or more of the sets of windings; and
a control module coupled to the sensor, the modulation module, and the motor driver module to:
operate the motor driver module to sequentially apply the modulated voltage to the one or more of the sets of windings in a particular order to produce a commanded number of motor steps of rotation by the rotor;
obtain a measured number of the incremental rotations from the sensor after the stepper motor is operated to provide the commanded number of motor steps;
increase the duty cycle for the modulated voltage in response to a difference between an expected number of incremental rotations corresponding to the commanded number of motor steps and the measured number of the incremental rotations; and
detect a degradation condition based on the duty cycle.

2. An infusion device, comprising:
a motor having a rotor;
a shaft mechanically coupled to the rotor, the shaft being displaced to deliver fluid in response to rotation of the rotor;
a modulation module coupled to the motor, the modulation module generating a modulated voltage applied to the motor, the modulated voltage oscillating between a first voltage and a second voltage, the modulated voltage being equal to the first voltage for a percentage of a time interval, the percentage corresponding to a duty cycle; and
a control module coupled to the modulation module to adjust the duty cycle to achieve a commanded rotation of the rotor and identify a degradation condition based on the duty cycle.

3. The infusion device of claim 2 , further comprising a sensor to obtain a measured displacement that is influenced by rotation of the rotor, wherein the control module is coupled to the motor and the sensor to operate the motor to provide the commanded rotation of the rotor while the modulated voltage is applied to the motor and adjust the duty cycle for the modulated voltage in response to a difference between an expected displacement corresponding to the commanded rotation the measured displacement obtained after operating the motor to provide the commanded rotation.

4. The infusion device of claim 3 , wherein the control module converts a commanded dosage into a commanded displacement of the shaft, the commanded rotation corresponding to the commanded displacement of the shaft.

5. A system comprising:
a motor having a rotor;
a modulation module coupled to the motor, the modulation module generating a modulated voltage applied to the motor, the modulated voltage oscillating between a first voltage and a second voltage, the modulated voltage being equal to the first voltage for a percentage of a time interval, the percentage corresponding to a duty cycle; and
a control module coupled to the motor and the modulation module to adjust the duty cycle to achieve a commanded rotation of the rotor and detect a degradation condition based on the duty cycle.

6. The system of claim 1 , wherein the control module detects the degradation condition when the duty cycle gradually increases over a period of time.

7. The system of claim 1 , wherein the first voltage comprises a supply voltage and the second voltage comprises a reference voltage.

8. The system of claim 1 , the modulated voltage comprising a square wave, wherein the duty cycle corresponds to a width of a portion of the square wave.

9. The system of claim 1 , wherein the control module detects the degradation condition when the duty cycle exceeds a reference value.

10. The system of claim 9 , wherein the reference value is a duty cycle unlikely to be exceeded unless the motor has degraded.

11. The system of claim 9 , wherein the reference value is a historical duty cycle average.

12. The system of claim 9 , wherein the control module dynamically determines the reference value during operation of the system.

13. The system of claim 1 , further comprising a motor driver module coupled between the modulation module and the motor to apply the modulated voltage to one or more sets of windings of the motor in a particular order to produce a corresponding number of commanded motor steps of rotation by the rotor, wherein the control module is coupled to the motor driver module to operate the motor driver module to provide the commanded rotation of the rotor while the modulated voltage is applied to the one or more sets of windings and increase the duty cycle for the modulated voltage in response to a difference between an expected displacement corresponding to the commanded rotation a measured displacement obtained after operating the motor driver module to provide the commanded rotation.

14. The system of claim 13 , wherein a frequency at which the motor driver module is operated to apply the modulated voltage to the one or more sets of windings is less than a frequency of the modulated voltage.

15. The system of claim 14 , wherein the frequency of the modulated voltage is greater than a time constant of the motor.

16. The system of claim 1 , further comprising a sensor to obtain a measured displacement that is influenced by rotation of the rotor, wherein the control module is coupled to the sensor to increase the duty cycle in response to a difference between an expected displacement and the measured displacement, wherein the expected displacement is based on the commanded rotation of the rotor.

17. The system of claim 16 , wherein:
the motor comprises a stepper motor;
the sensor comprises an incremental position sensor to detect incremental rotations of the rotor;
the measured displacement comprises a measured number of the incremental rotations after the motor is operated to provide the commanded rotation; and
the expected displacement comprises an expected number of the incremental rotations expected to be detected by the incremental position sensor after the motor is operated to provide the commanded rotation.

18. The system of claim 16 , wherein the control module operates the motor to provide the commanded rotation of the rotor while the modulated voltage is applied to the motor and increases the duty cycle for the modulated voltage in response to the difference between the expected displacement and the measured displacement.

19. The system of claim 18 , further comprising a shaft mechanically coupled to the rotor, wherein the commanded rotation corresponds to a commanded displacement of the shaft.

20. The system of claim 18 , wherein the control module operates the motor to compensate for the difference between the measured displacement and the expected displacement while the modulated voltage having the increased duty cycle is applied to the motor.

Assignees

• Medtronic Minimed Inc

Inventors

• Favreau Jacques L

Classifications

• H02P8/14 Primary

  Arrangements for controlling speed or speed and torque (H02P8/12, H02P8/22 take precedence) · CPC title

• A61M5/16804

  Flow controllers · CPC title

• H02P8/18

  Shaping of pulses, e.g. to reduce torque ripple {(Reducing overshoot H02P8/32 takes precedence)} · CPC title

• H02P29/032

  Preventing damage to the motor, e.g. setting individual current limits for different drive conditions · CPC title

• A61M5/1452 Primary

  pressurised by means of pistons · CPC title