Fast Commutation Error Compensation Method of Sensorless Control for MSCMG BLDC Motor With Nonideal Back EMF

Abstract

As aerospace applications, high reliability and low power consumption operation of the brushless direct current (BLDC) motor for the magnetically suspended control moment gyro (MSCMG) is the primary consideration. To guarantee reliability, the sensorless control without position sensors is adopted. Due to the phase lag caused by hardware and software, the commutation error is inevitable. In order to reduce losses, this article proposes a fast commutation error compensation method to improve commutation accuracy. First, the control topology of the BLDC motor with a buck converter and the commutation point detection circuit are presented. Then, the conducting back electromotive force (EMF) contained in a novel derived dc-link voltage expression is estimated through an extended state observer (ESO). Finally, the commutation error is extracted from the conducting back EMF for compensation. Different from the conventional closed-loop correction method based on the back EMF symmetry, the proposed commutation error compensation method can obtain the commutation error within only one commutation cycle by a continuous estimation with the ESO. The effectiveness of the proposed fast commutation error compensation method was evaluated with an MSCMG system.