Disk flutter and its impact on HDD servo performance

With rapid growth in storage density and spindle motor speed in hard disk drives (HDDs), disk flutter and its impact on drive performance is becoming a more and more important issue. Vibrations of disks used in 3.5" hard disk drives have been measured and studied. A model has been developed to translate disk motion measured in axial direction to actual head off-track motion. This model is constructed based on geometric modeling and FEM analysis of disk mode shapes. It has been validated by drive level position error signal (PES) measurements. Based on the model and flutter measurement, impact of disk flutter on PES has been studied and PES projection for various RPMs drives have been carried out.