Robustness analysis of position observers for permanent magnet synchronous motors vis-à-vis rotor saliency

A gradient descent-based nonlinear observer for surface-mount permanent magnet synchronous motors (PMSMs) with remarkable stability properties was recently proposed in [7]. A key assumption for the derivation of the observer is the absence of rotor saliency, which is the case in surface-mount PMSMs. Practically, PMSMs have saliencies from low level for surface-mount PMSMs to high level for internal-mount PMSMs. A question of great practical interest is to firstly assess the performance of the observer in the presence of saliency, and secondly to propose way of enhancement to take this effect into account. This is the topic of study of the present paper. We show in simulation the performance of the different observers.