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AssigneeSeagate Technology LLC
InventorJohn C. Dunfield
Estimating the term…
The present method and apparatus detects the rotor position of a brushless DC motor with an accuracy of .pi./m electrical radians (where m=the number of motor phases) within one electrical period, and provides enough information to enable starting the motor in the correct direction with certainty. After starting the motor in an open loop mode of one or two steps, a closed loop mode may be switched on, using a dynamic indirect position detection as is already well known in the technology. 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 time difference between the rise times of the induced voltages 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.
In a brushless DC motor having multiple phase windings arranged as a stator and a rotor having a permanent magnet or a DC current excitation winding, apparatus for controlling ordered application of electrical current to the phase windings and measuring the response thereto comprising:
The brushless DC motor of claim-4 wherein said reference level is variable and varied depending on said magnitude of said rise time difference.
A commutator less direct current motor comprising
The motor of claim -7 wherein said driver means connected to said plurality of windings for applying said short term current pulses to at least two different combinations of said phases thereof comprising at least on phase connected in series with at least a pair of said phases connected in parallel, for inducing at least two second, controlled magnetic fields.
In a brushless DC motor having multiple phase windings arranged as a stator and a rotor having a permanent magnet or a DC current excitation winding, a method for controlling ordered application of electrical current to the phase windings and measuring the response thereto to determine the initial position of said rotor comprising the steps of
Dependencies are inferred from the claim text.