Method and apparatus for driving a brushless DC motor without rotor position sensors
First Claim
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1. A method of operating a brushless dc motor, the motor including a plurality of motor windings, the method comprising the steps of:
- determining a back emf voltage across a non-conducting winding of the motor;
determining a voltage across a conducting winding of the motor;
determining an emf Park vector from the determined voltages;
extracting a component from the determined voltages; and
processing the component to determine when to perform commutation.
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Abstract
In a brushless dc motor, commutation is performed without the use of rotor position sensors. A voltage across a non-conducting winding of the motor is measured, a voltage across a conducting winding of the motor is computed, an emf Park vector is computed from the voltages, an imaginary component of a rotated emf Park vector is extracted, and the imaginary component is processed to determine when to perform the commutation from one winding to the next sequential winding.
55 Citations
19 Claims
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1. A method of operating a brushless dc motor, the motor including a plurality of motor windings, the method comprising the steps of:
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determining a back emf voltage across a non-conducting winding of the motor; determining a voltage across a conducting winding of the motor; determining an emf Park vector from the determined voltages; extracting a component from the determined voltages; and processing the component to determine when to perform commutation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system comprising:
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a brushless dc motor including a rotor and a plurality of windings, a back emf being induced in the windings when the rotor is rotated relative to the windings; an inverter including high and low switches for the windings; commutation logic for providing a sequence of gating commands that, when supplied in the sequence, cause the switches to selectively energize the windings to create a motor torque that causes the rotor to rotate; first means for measuring a back emf voltage across a non-conducting winding of the motor; second means for computing a voltage across a conducting winding of the motor; third means for extracting a component from the determined voltages; fourth means for processing the component to cause the commutation logic to supply the gating commands in the sequence,; and wherein the third means extracts the component by determining an imaginary component of a rotated emf Park vector. - View Dependent Claims (10, 11, 12, 13)
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14. A circuit for controlling an inverter coupled to a brushless dc motor, the motor including a plurality of motor windings, a back emf being induced in the windings when the rotor is rotated relative to the windings, the inverter including high and low switches for the windings, the circuit comprising:
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commutation logic for providing a sequence of gating commands that, when supplied in the sequence, cause the switches to selectively energize the windings to create a motor torque that causes the rotor to rotate; means for determining a Park vector of the motor; means for extracting a component of a rotated Park vector; and means for processing the component to cause the commutation logic to supply the gating commands in the sequence. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification