Direct self-control strategy for brushless DC motor with reduced torque ripple

This study proposed a direct self-control (DSC) strategy with reduced torque ripple for brushless DC motor (BLDCM). Taking the inherent advantage of DSC, sensorless control can be easily achieved from the relationship between commutation points of BLDCM and the hexagon-shape flux linkage locus. Furthermore, in the premise that position sensor is absent, excellent steady-state torque performance can also be achieved by the proposed strategy, which is achieved by increasing the degrees of control freedom through translation of switching point. In addition, another attractive feature lies in its relatively simpler control structure. Detailed analysis of torque ripple is carried out by deriving the expressions of torque variation rate through solving differential equations. Durations of voltage vectors are calculated to ensure the minimisation of torque ripple. The superiority of the proposed method is confirmed by comparative experiments.