Journal of Magnetism and Magnetic Materials 242–245 (2002) 1202–1205 Angular error analysis of an 8X-VR resolver with an eccentric rotor M. Nirei a, *, Y. Yamamoto a , K. Kitazawa b , Y. Kikuchi b , A. Kamiya c , H. Wakiwaka c a Nagano National College of Technology, 716 Tokuma, Nagano 381-8550, Japan b Tamagawa seiki Co., Ltd., 1879 Ohyasumi, Iida 395-8515, Japan c Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan Abstract This study clarifies the effects of rotor eccentricity and air-gap length of the 8X-VR resolver on revolution angle determination.Theeffectsarepredictedbymeansof2Dfiniteelementanalysis.Correlationsbetweencharacteristicsof the resolver and their parameters are also evaluated by means of multiple regression approaches. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Correlations; Finite element method; Sensors 1. Introduction A variable reluctance-type resolver (VR resolver) is a sensor,similartoarotarytransformer,whichconvertsa revolution angle into an electric signal. It is used widely in various fields due to its wide range operating temperature and its reliability. Its rotor has a curved- shapeonthecontourofpoleswhosenumberisequalto its angle multiplier. A VR resolver with a rotor which has an 8-pole contour (8X-VR resolver) has been developed as a sensor for the motor of electric vehicles [1,2]. Assembly error, which occurs during installation of the resolver, affects the accuracy of its revolution angle detection. It is necessary to clarify the relationship between rotor eccentricity and revolution angle detec- tion in order to reduce the variation in revolution angle determination due to the rotor eccentricity, which improves the accuracy of revolution angle detection. In this paper, we evaluate the variation on rotor revolution angle determination of the 8X-VR resolver which is caused by the rotor eccentricity, and describe the relationship between variation and parameters, such as the rotor eccentricity and the air-gap length between the rotor and the stator. 2. Structure of the 8X-VR resolver Fig.1showsthestructureofthe8X-VRresolver.The statoroftheresolverhas20salientpolesthatanexciting winding is wound on. Dual output windings are also wound on them with a phase difference of 90 degrees apart, and therefore these windings constitute a three- layer structure, as shown in Fig. 1(b). The rotor has 8 poles of smooth curve contour. The permeance of the gap between the stator and the rotor represents sinusoidal waveform according to the rotor revolution angle. When an AC voltage E is applied to the exciting winding, the output voltage equations are given as follows: V cos ¼ EK cos8y m ; ð1Þ V sin ¼ EK sin8y m ; ð2Þ *Corresponding author. E-mail address: nirei@ei.nagano-nct.ac.jp (M. Nirei). 0304-8853/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0304-8853(01)01298-7