Influence of Eccentricity on the Position Error of Variable Reluctance Resolvers Based on the Winding Function Method

The influence of static eccentricity (SE), dynamic eccentricity (DE), and mixed eccentricity (ME) on the position error of variable reluctance resolvers (VR-resolvers) is investigated in this study. First, an analytical model of VR-resolvers is established by the improved winding function (WF) method. Using the simplified air-gap function (AGF), the model is used to analyze the induced voltage of the resolver under fault conditions and the position error after decoding by the phase-locked loop (PLL) in the resolver-to-digital converter (RDC). The results indicate that all three types of eccentricity cause varying undesirable harmonics in the output voltage. SE and ME cause extra amplitude imbalance and dc offset. Besides, eccentricity can also generate current harmonics in the excitation winding, which can serve as a basis for eccentricity diagnosis. The angle position error after decoding by the PLL under different eccentricity conditions also differs. Finally, the theoretical analysis is validated by the simulation and experimental results. This study provides a reference for eccentricity diagnosis of VR-resolvers and benefits the researchers and designers in terms of rotor position error prediction and suppression of VR-resolvers.