Closed-loop control of a brushless DC motor from standstill to medium speed
First Claim
1. In a brushless direct current motor having multiple windings arranged as a stator and a permanent magnet rotor, apparatus for controlling ordered application of electrical current to the stator windings and measuring the response thereto comprising:
- circuit means coupled to said stator windings for selectively establishing current paths through a selected stator winding in response to control signals;
driver means for applying short duration current pulses of first and second opposite polarities to each said selected stator winding and for applying long duration current pulses to said selected stator winding to accelerate said magnetic rotor;
monitoring means for detecting the voltage detected at a current voltage converter connected to the energized phase;
detection means for identifying a rotational position of said magnetic rotor relative to said stator windings based on the sign of the difference between the response to said pulses applied to the same said selected stator winding; and
control means for controlling the periodic application of said short duration pulses based upon said rotational position of said magnetic rotor and for controlling the periodic application and duration of said long duration pulses based upon said rotational position of said magnetic rotor.
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Accused Products
Abstract
The present method and apparatus detects the position with an accuracy of π/m electrical radians (where m=the number of motor phases) within one electrical period, and provides enough information to be able to start in the correct direction with certainty.
More specifically, the position at start is determined by the injection of short current pulses in different motor phases, each phase or pair of phases being energized first by a pulse of one polarity and of the opposite polarity. The sign of the difference between the induced voltage is detected. By performing a succession of these tests on different phases or pairs of phases of the standing motor, a table of results is established which clearly defines the position of the rotor relative to the motor phases. The same table then defines what polarity currents should be applied to each phase to reliably and certainly start the motor in the proper direction.
Additionally, a method and apparatus is presented which uses the static position detection method to accelerate the motor to a medium speed. The method shortens the duration of the drive pulse as the motor accelerates ensuring a smooth acceleration without the possibility of back oscillation.
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Citations
28 Claims
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1. In a brushless direct current motor having multiple windings arranged as a stator and a permanent magnet rotor, apparatus for controlling ordered application of electrical current to the stator windings and measuring the response thereto comprising:
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circuit means coupled to said stator windings for selectively establishing current paths through a selected stator winding in response to control signals; driver means for applying short duration current pulses of first and second opposite polarities to each said selected stator winding and for applying long duration current pulses to said selected stator winding to accelerate said magnetic rotor; monitoring means for detecting the voltage detected at a current voltage converter connected to the energized phase; detection means for identifying a rotational position of said magnetic rotor relative to said stator windings based on the sign of the difference between the response to said pulses applied to the same said selected stator winding; and control means for controlling the periodic application of said short duration pulses based upon said rotational position of said magnetic rotor and for controlling the periodic application and duration of said long duration pulses based upon said rotational position of said magnetic rotor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 23, 27)
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8. In a brushless direct current motor having multiple windings arranged as a stator and a permanent magnet rotor, a method for controlling ordered periodic application of electrical current to said stator windings and measuring the response thereto to determine the initial position of said rotor and to accelerate said rotor to a medium speed comprising the steps of:
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coupling circuit means to said stator windings for selectively establishing current paths through a selected stator winding in response to control signals; applying short duration current pulses of first and second opposite polarities to each said selected stator winding; detecting the voltage detected at a current voltage converter to said selected stator winding by each of said applied current pulses of opposite polarities; identifying a rotational position of said magnetic rotor relative to said stator windings based on the sign of the difference between the response to said pulses applied to the same said selected stator winding; applying a first long duration current pulse to said selected stator winding based upon said identified rotational position of said magnetic rotor to accelerate said magnetic rotor; repeating said rotational position identification process to identify a new position of said magnetic rotor; applying a second long duration current pulse of a shorter duration than said first long duration current pulse to a new selected stator winding based upon said identified new rotational position of said magnetic rotor; repeating said rotational position identification process to identify a new position of said magnetic rotor and repeatedly applying said long duration current pulse with a shortened duration for each said repetition to a selected stator winding based on said new position of said magnetic rotor; ceasing said repetitive application of said long duration current pulses at such time that said long duration pulses are shortened to a predetermined duration; and applying a secondary technique to control the acceleration of said magnetic rotor upon ceasing application of said long duration current pulses. - View Dependent Claims (9, 10, 11, 24)
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12. In a brushless direct current motor having multiple windings arranged as a stator and a rotor having a direct current excitation rotor windings, apparatus for controlling ordered application of electrical current to said rotor windings and measuring said rotor windings thereto comprising:
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circuit means coupled to said rotor windings for selectively establishing current paths through a selected rotor winding in response to control signals; driver means for applying short duration current pulses of first and second opposite polarities to each said selected rotor winding and for applying long duration current pulses to said selected rotor windings to accelerate said magnetic rotor; monitoring means for detecting the voltage detected at a current voltage converter connected to the energized phase; detection means for identifying a rotational position of said magnetic rotor relative to said stator based on the sign of the difference between the response to said pulses applied to the same said selected rotor windings; and control means for controlling the periodic application of said short duration pulses based upon said rotational position of said magnetic rotor and for controlling the periodic application and duration of said long duration pulses based upon said rotational position of said magnetic rotor. - View Dependent Claims (13, 14, 15, 16, 17, 18, 25, 28)
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19. In a brushless direct current motor having multiple windings arranged as a stator and a rotor having a direct current excitation rotor winding, a method for controlling ordered periodic application of electrical current to said rotor windings and measuring the response thereto to determine the initial position of said rotor and to accelerate said rotor to a medium speed comprising the steps of:
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coupling circuit means to said rotor windings for selectively establishing current paths through a selected rotor winding or windings in response to control signals; applying short duration current pulses of first and second opposite polarities to each said selected rotor winding; detecting the voltage detected at a current voltage converter to said selected rotor winding by each of said applied current pulses of opposite polarities; identifying a rotational position of said magnetic rotor relative to said stator based on the sign of the difference between the response to said pulses applied to the same said selected rotor winging; applying a first long duration current pulse to said selected rotor winding based upon said identified rotational position of said magnetic rotor to accelerate said magnetic rotor; repeating said rotational position identification process to identify a new position of said magnetic rotor; applying a second long duration current pulse of a shorter duration than said first long duration current pulse to a new selected rotor winding based upon said identified new rotational position of said magnetic rotor; repeating said rotational position identification process to identify a new position of said magnetic rotor and repeatedly applying said long duration current pulse with a shortened duration for each said repetition to a selected rotor winding based on said new position of said magnetic rotor; ceasing said repetitive application of said long duration current pulses at such time that said long duration pulses are shortened to a predetermined duration; and applying a secondary technique to control the acceleration of said magnetic rotor upon ceasing application of said long duration current pulses. - View Dependent Claims (20, 21, 22, 26)
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Specification