Variable-Axis Extended Back-EMF Oriented Sensorless Method Based on Auxiliary Reference Frame SMO for MAS-IPMSM

In this article, the extended back-electromotive force (EMF) is generalized to variable-axis, by orienting toward which, a universal auxiliary reference frame sliding-mode observer (ARF-SMO) based sensorless method is proposed for magnet-axis-shifted interior permanent magnet synchronous motor (MAS-IPMSM). First, the variable-axis extended (VAE) back-EMF is proposed, which characterizes the information of the asymmetrical back-EMF due to magnet-axis-shifting (MAS) effect and unifies the back-EMF model of different rotor saliencies and symmetries. Subsequently, a universal ARF-SMO based sensorless method coping with MAS effect is proposed, in which the proposed auxiliary reference frame can obtain the unbiased position information by orienting toward the VAE back-EMF. The proposed ARF-SMO is a generalization of conventional SMO and keeps the universality for both MAS-IPMSM and typical PMSM. Additionally, the stability of the proposed ARF-SMO is proved based on the lyapunov theory. Finally, the effectiveness of the proposed method is verified with the experiments.