Robustness Analysis of a Position Observer for Surface-Mount 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. A question of great practical interest is to assess the performance of the observer in the presence of saliency. This is the topic of study of the present paper. It is shown that the robustness of the observer is fully determined by the sinusoidal steady-state values of the currents, providing some guidelines for the selection of their reference values to ensure good position estimation.