The spherical shell rotor is contained in the multi-degree-of-freedom permanent magnet synchronous motor. When the rated speed of motor is close to the critical speed, the motor will generate multiple resonances, which will affect the normal operation of the motor. The motor rotor must pass through the first-order critical speed and work at the safety range between 1-order and 2-order critical speed. According to the dynamic characteristics of rotor system, a mathematical model of rotor under free state is established, and the result between finite element and analytical methods is comparison. The influence of rotor gyroscope effect on critical speed is analyzed, and the finite element analysis of whether the rigidity of rotor material affects the critical speed is also carried out. The relationship between bending modal and deformation displacement is tested under different rigidity conditions and the stator deformation caused by rotor rotation is analyzed when the stator is filled with different liquids. The relationship between the rotational speed and the amplitude of the spherical rotor is verified by experiments, and the corresponding rules are summarized. The results of the simulation and analysis are referenced by the optimal design of motor.

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Based on the combination of elastohydrodynamic lubrication and contact deformation theory, i.e. fluid-solid coupling theory, and considering the surface roughness of stator and rotor, a three-degree-of-freedom vibration model of spherical bearings with spiral grooves is established. The finite difference method is used to calculate and analyze the distribution of lubricating film pressure, film thickness and the influence of eccentricity of rotor on film pressure. Combining the stiffness of lubricating oil film with the finite element method, the displacement, stator vibration speed, acceleration and displacement of lubricating oil film are calculated from the angle of elastic boundary, and compared with the slotless structure. The results show that the bearing capacity of lubricating oil film of spherical bearing is improved and the stability of continuous oil film is improved by adding spiral groove. Secondly, the vibration characteristics of stator and rotor with spiral groove structure are more in line with the viscoelastic periodic distribution law. The vibration stability of the system is improved. In order to further optimize the vibration stability of the motor, the theoretical basis is provided.

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