Compressor control system for a portable ventilator

• US 8,677,995 B2
• Filed: 10/23/2007
• Issued: 03/25/2014
• Est. Priority Date: 08/04/2003
• Status: Active Grant

• Current Assignee: Vyaire Medical 203 Incorporated (Cardinal Health, Inc.)
• Original Assignee: Carefusion 303 Incorporated (Becton, Dickinson & Co)
• Inventors: Boyle, David, Holmes, Michael, Williams, Malcolm
• Primary Examiner(s): Dixon, Annette
• Application Number:
  US11/877,117
• Publication Number:
  US 20080092892A1
• Time in Patent Office: 2,345 Days
• Field of Search: 128/200.24, 128/204.18, 128/204.21, 128/204.19, 318/808, 318/400.14, 318/400.11, 318/400.01, 318/400.04, 318/400.09, 318/400.15, 318/400.17, 318/400.22, 318/400.37, 318/400.38, 73/14.1, 388/800, 388/809, 388/803, 388/806, 700/282
• US Class Current: 128/204.21
• CPC Class Codes: A61M 11/00 Sprayers or atomisers specially adapted for therapeutic purposes in general B05B; aerosol containers B65D83/14
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0057 Pumps therefor
• CPC Class Codes: A61M 16/0063 Compressors
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 16/107 in the inspiratory path
• CPC Class Codes: A61M 16/12 by mixing different gases
• CPC Class Codes: A61M 16/202 electrically actuated
• CPC Class Codes: A61M 16/205 used for exhalation control
• CPC Class Codes: A61M 16/206 Capsule valves, e.g. mushroom, membrane valves
• CPC Class Codes: A61M 16/209 Relief valves
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2016/1025 the O2 concentration
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2205/16 with back-up system in case of failure
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means
• CPC Class Codes: A61M 2205/3365 Rotational speed
• CPC Class Codes: A61M 2205/3368 : Temperature
• CPC Class Codes: A61M 2205/3553 : remote, e.g. between patient's home and doctor's office
• CPC Class Codes: A61M 2205/3569 : sublocal, e.g. between console and disposable
• CPC Class Codes: A61M 2205/3584 : using modem, internet or bluetooth
• CPC Class Codes: A61M 2205/42 : Reducing noise
• CPC Class Codes: A61M 2205/505 : Touch-screens; Virtual keyboard or keypads; Virtual buttons; Soft keys; Mouse touches
• CPC Class Codes: A61M 2205/52 : with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2205/581 : by audible feedback
• CPC Class Codes: A61M 2205/583 : by visual feedback
• CPC Class Codes: A61M 2205/70 : with testing or calibration facilities
• CPC Class Codes: A61M 2205/8206 : battery-operated
• CPC Class Codes: A61M 2205/8237 : Charging means
• CPC Class Codes: A61M 2205/8262 : connectable to external power source, e.g. connecting to automobile battery through the cigarette lighter
• CPC Class Codes: A61M 2209/086 : Docking stations
• CPC Class Codes: A61M 2230/205 : partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/432 : partial CO2 pressure (P-CO2)
• CPC Class Codes: A61M 2230/435 : partial O2 pressure (P-O2)
• CPC Class Codes: H02P 6/17 : and for generating speed information

Abstract

A method and apparatus for controlling a brushless DC (BLDC) motor over a wide range of angular speeds is presented. Analog magnetic sensors provide continuous signal measurements related to the rotor angular position at a sample rate independent of rotor angular speed. In one embodiment, analog signal measurements are subsequently processed using an arctangent function to obtain the rotor angular position. The arctangent may be computed using arithmetic computation, a small angle approximation, a polynomial evaluation approach, a table lookup approach, or a combination of various methods. In one embodiment, the BLDC rotor is used to drive a Roots blower used as a compressor in a portable mechanical ventilator system.

Claims

1. A portable ventilator apparatus comprising:

a compressor disposed within the portable ventilator;

a brushless direct current (BLDC) motor, said compressor driven by said BLDC motor;

a plurality of sensors disposed within the portable ventilator that provide a plurality of analog signals, said plurality of analog signals representative of an angular position of said BLDC motor;

a computation circuit disposed within the portable ventilator and in communication with the plurality of sensors configured to compute said angular position or an angular speed of said BLDC motor from said plurality of analog signals; and

a speed control servo disposed within the portable ventilator and in communication with said BLDC motor for driving said angular speed of the BLDC motor to a command speed provided to said computation circuit;

an analog to digital converter directly coupled with said plurality of sensors that directly receives the analog signals provided by said plurality of sensors, and that converts the analog signals to digital signals, and that outputs the digital signals;

a processor that receives the digital signals, that generates control signals based on the digital signals, and that provides the control signals to a three phase inverter that generates drive signals to control said BLDC motor.

2. The apparatus of claim 1, wherein said BLDC motor includes a plurality of stator coils that receive said drive signals.

3. The apparatus of claim 1, wherein said plurality of sensors includes pressure sensors.

4. A method for controlling a portable ventilator comprising:

receiving directly one or more analog sensor signals having an amplitude related to an angular position of a rotor of a brushless direct current (BLDC) motor at an analog to digital converter from one or more analog sensors directly coupled with said analog to digital converter;

converting the analog signals into digital signals via the analog to digital converter;

processing the digital signals to obtain current information about the speed of the BLDC motor via a processor;

generating control signals to control the speed of the BLDC motor;

controlling the speed of the BLDC motor with the control signals to drive a compressor of said portable ventilator.

5. The method of claim 4, wherein the BLDC motor drives said compressor to produce a flow-rate to a patient to achieve a specific waveform or pressure profile.

6. The method of claim 4, wherein the BLDC motor drives said compressor to produce a flow-rate to a patient to deliver a specific volume of air.

7. A method for controlling a portable ventilator comprising:

receiving directly one or more analog sensor signals having an amplitude related to an angular position of a rotor of a brushless direct current (BLDC) motor at an analog to digital converter from one or more analog sensors directly coupled with said analog to digital converter;

converting the analog signals into digital signals via the analog to digital converter;

processing the digital signals to obtain current information about the position of the BLDC motor via a processor;

generating control signals to control the position of the BLDC motor;

controlling the position of the BLDC motor with the control signals to drive a compressor of said portable ventilator.

8. The method of claim 7, wherein the BLDC motor drives said compressor to produce a flow-rate to a patient to achieve a specific waveform or pressure profile.

9. The method of claim 7, wherein the BLDC motor drives said compressor to produce a flow-rate to a patient to deliver a specific volume of air.

10. A method for controlling a portable ventilator comprising:

setting a desired peak pressure;

measuring an actual output pressure;

receiving directly one or more analog sensor signals having an amplitude related to an angular position of a rotor of a brushless direct current (BLDC) motor at an analog to digital converter from one or more analog sensors directly coupled with said analog to digital converter;

converting the analog signals into digital signals via the analog to digital converter;

calculating a difference between the desired peak pressure and the actual output pressure; and

controlling the speed of a brushless direct current (BLDC) motor to drive a blower of said portable ventilator to output the desired peak pressure;

wherein controlling the speed includes calculating said angular position of the motor.

11. The method of claim 10, wherein the difference between the desired peak pressure and the actual output pressure is regulated by proportional-integral-derivative controllers.

12. The method of claim 10, wherein the difference between the desired peak pressure and actual output pressure is regulated using pressure to flow rate conversion factors.

13. The method of claim 10, wherein the speed of said BLDC motor controls the flow rate of the output of said blower, which in turn controls the output pressure.

14. A method for controlling a portable ventilator comprising:

setting a desired flow-rate;

calculating an actual flow-rate;

receiving directly one or more analog sensor signals having an amplitude related to an angular position of a rotor of a brushless direct current (BLDC) motor at an analog to digital converter from one or more analog sensors directly coupled with said analog to digital converter;

converting the analog signals into digital signals via the analog to digital converter;

calculating a difference between the desired flow-rate and the actual flow-rate;

controlling the speed of a brushless direct current (BLDG) motor to drive a blower of said portable ventilator to output the desired flow-rate;

wherein controlling the speed includes calculating said angular position of the motor.

15. The method of claim 14, wherein the actual flow rate is calculated through estimation by using a computed motor speed and a measured blower differential pressure in a blower characteristic function.

16. The method of claim 15, wherein the blower characteristic function is determined empirically.

17. The method of claim 14, wherein the difference between the desired flow-rate and the actual flow rate includes circuitry implementing a proportional controller.

18. The method of claim 14, wherein the difference between the desired flow-rate and the actual flow rate includes circuitry implementing an integral controller.

19. The method of claim 14, wherein the difference between the desired flow-rate and the actual flow rate includes circuitry implementing a derivative controller.

20. The method of claim 14, wherein the difference between the desired flow rate and the actual flow rate includes circuitry implementing proportional-integral-derivative controllers.

21. The method of claim 14, wherein the difference between the desired flow rate and the actual flow rate includes circuitry implementing proportional-integral-derivative controllers with feed forward term.

22. The method of claim 14, wherein the speed of the BLDC motor is controlled by a speed servo.