Magnetically induced vibration of a flexible rotating disk-spindle system due to the internal magnetic force arising from the spindle motor of a HDD

Abstract

This paper investigates the magnetically induced vibration of a flexible rotating disk-spindle system and stationary stator-base due to the internal excitation of the local magnetic force arising from the spindle motor of a HDD. A three-dimensional magnetic finite element model of the spindle motor is developed, and the Maxwell stress tensor method is applied to calculate the local magnetic force acting on the stationary teeth and rotating permanent magnet of the spindle motor. Also, a three-dimensional structural finite element model is developed and local magnetic force is applied to teeth and permanent magnet. The simulated forced vibration of the base plate matched well with the measured one. The dominant frequency component of local magnetic force is the 12th harmonic corresponding to the number of poles, but the dominant frequency component of vibration is the 36th harmonic corresponding to the least common multiple of the number of poles and slots because the 12 and 24th harmonics in local force are canceled out when they are summed up along the air gap. The 12th, 24th and 36th harmonics of the axial vibration are mostly affected by the axial magnetic force, and the amplitudes of those harmonics are increased with the increase of stator eccentricity.