Torque ripple compensation circuit for a brushless D.C. motor

Claim 1

Rotation control apparatus for an electronic commutator motor, said electronic commutator motor comprising a predetermined plural number of stator coils disposed with a predetermined mechanical angle around an axis of rotation of said electronic commutator motor, a rotor magnet which has a predetermined number of magnetic poles of N and S disposed alternately with predetermined mechanical angles and held in a rotatable manner around said axis, and a rotation position signal output means for issuing a rotation position signal responding to mechanical rotation of said rotor magnet relative to said stator coils, wherein said rotation control apparatus comprises: a rotation fine position signal output means for issuing a rotation fine position signal consisting of a predetermined number of pulses during one period of repetition of said rotation position signal in a synchronized relation with the rotation position signal, a rotation fine position signal counter for producing an electric angle signal which is a signal responding to number of pulses of said rotation fine position signal counted from each time when a pulse of said rotation position signal is issued by receiving said rotation fine position signal, memory means which has preliminarily stored data of compensation function for compensating amount of stator current to compensate torque ripple, to produce uniform torque, and produces a data responding to said electric angle signal, gain control means for controlling intensities of said stator coils responding to said output of said memory means, to produce compensated uniform current in said stator coils.