ROTOR POSITION DETECTION OF A BRUSHLESS DC MOTOR

WIPO Patent Application WO2005096491

A8

A method of determining the angular position of the rotor of a brushless direct current motor having a stator with multi-phase windings, a control circuitry that provides excitations switched after one another to the motor phases such that excitations produce stator flux vectors lying in different directions in the full 360 electrical degree range, and a measurement circuitry that delivers responses for the phase excitations characterised inthat the position is estimated by selecting the main excitation stator flux vector which results in the minimal inductivity shown by the measured response and selecting the two other vectors in the previous and subsequent directions with respect to the direction of the main vector, and by computing the ratio between differences of measured responses for the selected stator flux vectors.