Analysis of FSCW SPM servo motor with static, dynamic and mixed eccentricity in aspects of radial force and vibration

This paper deeply discusses the effect of eccentricity, including static, dynamic and mixed eccentricity on the performance of FSCW SPM servo motor analytically and using finite element analysis (FEA) to validation. The effect of different kinds of eccentricity on magnetic field including magnet field and armature reaction field is described with three factor called modulation factor. The frequency and spatial mode order of radial force for static, dynamic and mixed eccentricity are analyzed and summarized with the analytical method and validated by FEA. It is found that compared with health machine, the frequency and mode order of radial force distort for eccentric machine: the static eccentricity (SE) extends the mode order but the frequency invariant while the dynamic eccentricity (DE) and mixed eccentricity (ME) change both the frequency and mode order of radial force. With the electromagnetic radial force obtained, we predict the vibration of the stator housing, and acoustic noise around the machine. The results show that due to the smallest spatial mode decrease and frequency spectra extension, the eccentric machines will have a large vibration both on load and without load for easier to resonance at some natural frequency compared with health machine. As a consequence, the noise level of eccentric machine will also enlarge. The analysis results is verified by experiment and can be explained reasonably. The work of this paper is helpful to design and analyze the motor which is used in the servo drive system and other similar occasions.