Compressor control system and method for a portable ventilator
First 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.
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Accused Products
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.
225 Citations
27 Claims
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1. A method for controlling a portable ventilator comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A portable ventilator apparatus comprising:
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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. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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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:
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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. - View Dependent Claims (26)
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27. A method for controlling a portable ventilator comprising:
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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.
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Specification