Fault-Tolerant Control of Brushless DC Motors Under Static Rotor Eccentricity

In some industries, continuous operation of motors even under faults until scheduled maintenance time is necessary. However, conventional control methods are inefficient for eccentricity faults. In a conventional brushless direct current (BLDC) motor control method, stator current commands are similar in shape and delayed by corresponding phase differences in each phase. However, if the actual shape of the back electromotive force (EMF) waveform of an eccentric motor and phase inductance variations due to eccentricity are not considered, undesirable torque ripples may occur. Hence, a new control strategy must be developed for improving motor performance. In this paper, a method for controlling BLDC motors under static rotor eccentricity is proposed. The proposed control method is based on online estimation of phase inductances and back-EMFs of the BLDC motor under eccentricity faults. Therefore, in contrast to conventional methods, stator currents are injected considering the estimated back-EMFs of the conducting phases. The experimental results verify that the proposed method reduces electromagnetic torque pulsations under static rotor eccentricity.