Magnetic field analysis of a resolver with a skewed and eccentric rotor

Abstract

Factory automation applications such as machine tools, etc., with high precision motion control require a feedback sensor with low speed-ripple for precise velocity control. The resolver is one of feedback sensors widely used in automation applications. Distorted signal-output related to speed fluctuations of the resolver result from permeance ripples, etc., produced by eccentricity of the rotor and stator slots in which coils are installed, and of the rotor itself. Although the permeance method has been used to analyze and determine the optimal magnetic design of a resolver, it remains an imperfect solution. This paper proposes a new magnetic field analysis method which offers the means to produce better analysis. The most significant feature of our method is that the skewed resolver rotor is divided into segments and the induced voltages of each segments are calculated and combined. Therefore, the analysis of the skew affect and the eccentricity of the rotor becomes possible by using the 2-D FEM (two-dimensional finite element method) with magnetic vector potential. The analyzed results of the spectrum in the induced dual phase voltage waveforms indicate the possibilities of close agreement with the measured values. These results confirm the validity of this method.