Closed-loop control of a brushless DC motor from standstill to m

Details Closed-loop control of a brushless DC motor from standstill to m Closed-loop control of a brushless DC motor from standstill to m

1990-06-29

1992-05-26

Smith, Jr., David

Electricity: motive power systems

Switched reluctance motor commutation control

318138, H02P 662, H02K 2900

Patent

active

051171651

ABSTRACT:
The present method and apparatus detects the position with an accuracy of .pi./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.

REFERENCES:
patent: 3909688 (1975-09-01), Blaschke et al.
patent: 4641066 (1987-02-01), Nagata et al.
patent: 4746850 (1988-05-01), Abbonoanti
patent: 4876491 (1989-10-01), Squires et al.
patent: 4992710 (1991-02-01), Cassat
patent: 5001405 (1991-03-01), Cassat

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