Disk flutter and its impact on HDD servo performance

With rapid growth in storage density and spindle motor speed in hard disk drives (HDD's), disk flutter and its impact on drive performance is becoming a more and more important issue. In this study, vibrations of disks used in 3.5" hard disk drives with different thickness have been measured. A model has been developed to translate disk motion measured in vertical direction to actual head off-track motion. This model was constructed based on geometric modeling and FEM analysis of disk mode shapes. It was then validated by drive level position error signal (PES) measurements. Based on the model and flutter measurement, the TMR impact of the flutter after servo has been studied and the PES projection for drives with different spindle speeds have been carried out.