Method and system for motor failure detection

• US 20080251071A1
• Filed: 04/11/2008
• Published: 10/16/2008
• Est. Priority Date: 04/13/2007
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Armitstead, Jeffrey Peter, Martin, Dion Charles Chewe, Somerville, William Mcinnes
• Granted Patent: US 9,119,923 B2
• Time in Patent Office: Days
• US Class Current: 128/202.22
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2205/103 rotating
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3365 Rotational speed
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2205/702 automatically during use
• CPC Class Codes: F04B 51/00 Testing machines, pumps, or pumping installations
• CPC Class Codes: G01R 31/34 Testing dynamo-electric machines
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: H02K 11/20 for measuring, monitoring, testing, protecting or switching rectifiers H02K11/04; power electronics H02K11/33
• CPC Class Codes: H02P 29/02 Providing protection against overload without automatic interruption of supply protection against faults of stepper motors H02P8/36

Abstract

Systems and methods for detecting developing faults in a flow generator or ventilator during therapeutic use thereof are provided. The motor current may be measured to estimate the torque input by the motor, while the output torque from the impeller may be determined (e.g., as inferred from the motor control system model and/or by consulting a lookup table). One or more transducers may collect data useful in determining the input and output torques. A difference between the input (to the motor) torque and the output (from the impeller) torque may be calculated. The difference, optionally filtered using a low-pass filter to reduce noise, may be compared to a predetermined threshold once or over a period of time to detect gross failures and/or developing failures. Once a failure or developing failure is detected, a user may be alerted and/or the flow generator may be placed into a “service required” mode.

Claims

1. A method of detecting developing faults in a flow generator having an impeller powered by a motor under servo-control during therapeutic use of the flow generator, the method comprising:

measuring motor current;

determining an actual motor torque generated by the motor based at least in part on the motor current;

determining an expected motor torque;

calculating a difference between the expected torque load and the actual motor torque; and

,

assessing whether a fault exists based at least in part on the difference.

2. The method of claim 1, wherein the determination of the actual motor torque is further based on an inference from a motor control system model.

3. The method of claim 1, wherein the determination of the actual motor torque is further based on a motor control system lookup table.

4. The method of claim 1, further comprising when a fault exists, activating an alert and/or placing the flow generator into a service required mode.

5. The method of claim 1, further comprising comparing the difference to a predetermined threshold.

6. The method of claim 5, further comprising when the difference exceeds the predetermined threshold for a specified amount of time, indicating that a fault exists.

7. The method of claim 1, further comprising filtering the difference with a low-pass filter.

8. The method of claim 7, wherein the low-pass filter is configured to reduce transient errors.

9. The method of claim 7, further comprising comparing the filtered difference to a predetermined threshold.

10. The method of claim 7, further comprising when the difference exceeds the predetermined threshold for a specified amount of time, indicating that a fault exists.

11. The method of claim 1, further comprising correcting for variations in one or more of ambient pressure, temperature, and viscosity.

12. The method of claim 1, further comprising measuring outputs from a turbine of the motor, the measured outputs including pressure, flow, and/or rotational speed, and

wherein the determination of expected motor torque is based at least in part on the measured outputs.

13. A turbine-based ventilator device, comprising:

a motor capable of being powered by an impeller; and

,

a closed-loop controller for the motor/impeller,

wherein the controller is further configured to indicate the presence of developing faults of the device during therapeutic use of the device based on a comparison of actual motor torque and expected torque load.

14. The device of claim 13, further comprising a flexible conduit connected to a mask, the conduit and the mask being suitable for conveying a supply of pressurized breathable gas to a patient.

15. The device of claim 13, further comprising a transconductance amplifier configured to measure motor current.

16. The device of claim 13, further comprising at least one transducer capable of measuring and/or calculating:

pressure delivered to a patient, flow, rotational speed of the impeller, and motor current.

17. The device of claim 13, wherein the determination of the actual motor torque is based on motor current and/or an inference from a motor control system model.

18. The device of claim 13, wherein the determination of the actual motor torque is based on motor current and/or a motor control system lookup table.

19. The device of claim 13, further comprising a low-pass filter configured to filter the comparison.

20. The device of claim 19, wherein the low-pass filter is configured to reduce transient errors.

21. The device of claim 13, wherein when a fault exists, the controller is further configured to activate an alert and/or place the device into a service required mode.

22. The device of claim 13, wherein the comparison is a difference between the expected torque load and the actual motor torque.

23. The device of claim 22, wherein the controller is further configured to compare the difference to a predetermined threshold.

24. The device of claim 23, wherein when the difference exceeds the predetermined threshold for a specified amount of time, the controller is further configured to indicate that a fault exists.

25. The device of claim 19, wherein the controller is further configured to compare the filtered comparison to a predetermined threshold.

26. The device of claim 25, wherein when the filtered comparison exceeds the predetermined threshold for a specified amount of time, the controller is further configured to indicate that a fault exists.

27. The device of claims 13, wherein the controller is configured to instruct the motor to correct for variations in ambient pressure and/or temperature.

28. The device of claim 13, wherein turbine-based ventilator is a flow-target, volume-target, and/or pressure-target device.

29. The device of claim 13, wherein the turbine-based ventilator device is a PAP device.