Effect of the pivot assembly on the dynamic behaviour of a head actuator in hard disk drives

Vibration/dynamics studies have become increasingly important in the mechan ical design of hard disk drives (HDDs) owing to the ever-growing demand for greater storage density and access speed. In fact, it is anticipated that it is the vibration/dynamic characteristics of HDD assemblies that will eve ntually pose a design limit on their performance, not the associated electr onics whose designs are far more advanced. In this study, finite element an alysis is used to model and investigate the dynamic behaviour of a head act uator with consideration of the effect of pivot assembly. Then, an experime ntal method for measuring the vibration/dynamics of the head actuator is de veloped using the Ometron VPI laser sensor system. The representative vibra tion modes that limit the servo bandwidth are identified and analysed. The effect of pivot assembly on the vibration modes of the head actuator is stu died under different conditions. From the results of numerical analysis and experimental demonstration, it is shown that pivot assembly is an importan t factor that limits the servo bandwidth and access speed of the head actua tor. Based on these studies, a new passive damping structure, which is atta ched to the housing of the pivot assembly, is proposed, and its feasibility for improving the dynamic behaviour of the head actuator is theoretically proved.