# US 7,607,437 B2 · Compressor control system and method for a portable ventilator

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- Number: US 7,607,437 B2
- Document ID: US7607437B2
- Status: Granted
- Kind: B2
- Application number: 10/847,693
- Filed: 2004-05-18
- Published: 2005-02-10
- Granted: 2009-10-27
- Earliest claimed: 2003-08-04
- Assignees: Cardinal Health 203, Inc.
- Inventors: David Boyle; Michael Holmes; Malcolm Williams
- Web page: https://patentgrep.com/patent/US7607437B2

## CPC

- A61M 16/0051: {with alarm devices}
- A61M 16/0057: {Pumps therefor}
- A61M 16/0063: {Compressors}
- A61M 16/0069: {the speed thereof being controlled by respiratory parameters, e.g. by inhalation}
- 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}
- A61M 16/202: {electrically actuated}
- A61M 16/205: {used for exhalation control}
- A61M 16/206: {Capsule valves, e.g. mushroom, membrane valves}
- H02P 6/17: and for generating speed information
- A61M 11/00: Sprayers or atomisers specially adapted for therapeutic purposes (in general B05B; {aerosol containers B65D83/14})
- A61M 16/0066: {Blowers or centrifugal pumps}
- A61M 16/107: {in the inspiratory path}
- A61M 16/12: by mixing different gases
- A61M 16/209: {Relief valves}
- A61M 2016/0021: {with a proportional output signal, e.g. from a thermistor}
- A61M 2016/0036: {in the breathing tube and used in both inspiratory and expiratory phase}
- A61M 2016/1025: {the O2 concentration}
- A61M 2202/0208: Oxygen
- A61M 2205/16: with back-up system in case of failure
- A61M 2205/3317: Electromagnetic, inductive or dielectric measuring means
- A61M 2205/3365: Rotational speed
- A61M 2205/3368: Temperature
- A61M 2205/3553: remote, e.g. between patient's home and doctor's office
- A61M 2205/3569: sublocal, e.g. between console and disposable
- A61M 2205/3584: using modem, internet or Bluetooth®
- A61M 2205/42: Reducing noise
- A61M 2205/505: Touch-screens; Virtual keyboard or keypads; Virtual buttons; Soft keys; Mouse touches
- A61M 2205/52: with memories providing a history of measured variating parameters of apparatus or patient
- A61M 2205/581: by audible feedback
- A61M 2205/583: by visual feedback
- A61M 2205/70: with testing or calibration facilities
- A61M 2205/8206: battery-operated
- A61M 2205/8237: Charging means
- A61M 2205/8262: connectable to external power source, e.g. connecting to automobile battery through the cigarette lighter
- A61M 2209/086: Docking stations
- A61M 2230/205: partial oxygen pressure (P-O2)
- A61M 2230/432: partial CO2 pressure (P-CO2)
- A61M 2230/435: partial O2 pressure (P-O2)
- A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)}
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## 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

### Claim 1

A method for controlling a portable ventilator comprising:
obtaining one or more analog sensor signals having an amplitude related to an angular position of a rotor of a brushless DC (BLDC) motor;
computing an angular position of said rotor from said analog sensor signals;
computing an angular speed from said angular position;
applying said angular speed in a speed control servo for said BLDC motor;
computing a speed error based on said angular speed with a desired angular speed; and
driving a compressor of a portable ventilator with said BLDC motor by adjusting said angular speed to match said desired angular speed in accordance with said speed error during operation of the BLDC motor.

### Claim 2 (depends on 1)

The method of claim 1, wherein said analog sensor signals are obtained using analog Hall effect sensors.

### Claim 3 (depends on 1)

The method of claim 1, wherein said analog sensor signals are obtained from anisotropic magneto-resistive (AMR) sensors.

### Claim 4 (depends on 1)

The method of claim 1, wherein said angular position is obtained by computing an arctangent of said analog sensor signals.

### Claim 5 (depends on 1)

The method of claim 1, wherein said angular speed is obtained by differentiating said angular position.

### Claim 6 (depends on 1)

The method of claim 1, wherein said compressor comprises a Roots blower.

### Claim 7 (depends on 1)

The method of claim 1, wherein said analog sensor signals are obtained at a constant sample rate.

### Claim 8 (depends on 1)

The method of claim 1, wherein computing said angular position comprises:
obtaining a first analog sensor signal from a first analog sensor;
obtaining a second analog sensor signal from a second analog sensor displaced from said first analog sensor by 180 degrees; and
subtracting said second analog sensor signal from said first analog sensor signal.

### Claim 9 (depends on 1)

The method of claim 1, wherein computing said angular position comprises applying a DC offset correction to said one or more analog sensor signals.

### Claim 10 (depends on 1)

The method of claim 1, wherein computing said angular position comprises applying a commutation correction angle to a computed position value.

### Claim 11 (depends on 1)

The method of claim 1, wherein computing said angular position comprises:
identifying a current quadrant of rotation;
obtaining stored coefficients for said current quadrant; and
solving a polynomial equation with said current coefficients and a plurality of digitized sensor readings.

### Claim 12

A portable ventilator apparatus comprising:
a brushless DC (BLDC) motor;
a compressor within a portable ventilator, said compressor driven by said BLDC motor;
a plurality of sensors providing a plurality of analog signals representative of an angular position of said BLDC motor;
a computation circuit configured to compute said angular position and a speed of said BLDC motor from said plurality of analog signals; and
a speed control servo for driving said angular speed, during operation of the BLDC motor, in accordance with a command speed based on a difference between said angular speed and a desired speed.

### Claim 13 (depends on 12)

The apparatus of claim 12, wherein each of said plurality of sensors comprises an analog Hall effect sensor.

### Claim 14 (depends on 12)

The apparatus of claim 12, wherein each of said plurality of sensors comprises an anisotropic magneto-resistive (AMR) sensor.

### Claim 15 (depends on 12)

The apparatus of claim 12, wherein said plurality of analog sensors comprises four analog sensors arranged ninety degrees apart from each other in a circular pattern.

### Claim 16 (depends on 12)

The apparatus of claim 12, wherein said command speed is calculated by a flow-rate control loop to provide a required flow-rate through said compressor.

### Claim 17 (depends on 16)

The apparatus of claim 16, wherein said required flow rate is calculated by a pressure control function.

### Claim 18 (depends on 12)

The apparatus of claim 12, wherein said computation circuit comprises a processor.

### Claim 19 (depends on 12)

The apparatus of claim 12, wherein said computation circuit computes said angular position from said plurality of analog signals using an arctangent function.

### Claim 20 (depends on 12)

The apparatus of claim 12, wherein said computation circuit computes said angular position from said plurality of analog signals using a table lookup function.

### Claim 21 (depends on 12)

The apparatus of claim 12, wherein said computation circuit computes said angular position from said plurality of analog signals using polynomial evaluation.

### Claim 22 (depends on 12)

The apparatus of claim 12, further comprising an analog-to-digital converter which samples said plurality of analog signals at a constant sample rate, and which provides corresponding digital values to said computation circuit.

### Claim 23 (depends on 12)

The apparatus of claim 12, wherein said computation circuit comprises a plurality of stored coefficient values for computing said angular position from a polynomial equation.

### Claim 24 (depends on 23)

The apparatus of claim 23, wherein said plurality of coefficient values comprises a set of coefficients associated with each quadrant of a rotation.

### Claim 25

A method for controlling an electric motor comprising a plurality of analog sensors sensing a magnetic flux associated with rotation of a rotor, said method comprising:
sampling the outputs of said plurality of analog sensors to obtain a plurality of digitized sensor signals, said sampling occurring at a constant sample rate;
subtracting a first digitized signal associated with a first sensor from a second digitized signal associated with a second sensor to obtain a first sinusoidal value related to an angular position of said rotor, said first sensor and said second sensor offset from each other by 180 degrees;
deriving said angular position from said first sinusoidal value;
deriving said angular speed from said angular position;
during operation of the motor, applying said derived angular speed to an airflow control loop to obtain a desired angular speed from a desired airflow,
applying said derived angular speed to a speed control servo to drive said rotor at said desired angular speed; and
wherein said electric motor is used to drive a compressor of a mechanical ventilator.

### Claim 26 (depends on 25)

The method of claim 25, further comprising comparing a desired pressure with a measured pressure to obtain said desired airflow.

### Claim 27

A method for controlling a portable ventilator comprising:
obtaining an analog sensor signal having an amplitude related to an angular position of a rotor of a brushless DC (BLDC) motor;
computing an angular position of the rotor from the analog sensor signal;
computing an angular speed from the angular position;
controlling the rotor speed of the BLDC motor according to a desired speed, the desired speed being derived based on the angular speed, during operation of the BLDC motor; and
driving a compressor of the portable ventilator with the BLDC motor.