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

Abstract Vibration/dynamics studies have become increasingly important in the mechanical 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 eventually pose a design limit on their performance, not the associated electronics whose designs are far more advanced. In this study, finite element analysis is used to model and investigate the dynamic behaviour of a head actuator with consideration of the effect of pivot assembly. Then, an experimental method for measuring the vibration/dynamics of the head actuator is developed using the Ometron VPI laser sensor system. The representative vibration modes that limit the servo bandwidth are identified and analysed. The effect of pivot assembly on the vibration modes of the head actuator is studied under different conditions. From the results of numerical analysis and experimental demonstration, it is shown that pivot assembly is an important factor that limits the servo bandwidth and access speed of the head actuator. Based on these studies, a new passive damping structure, which is attached to the housing of the pivot assembly, is proposed, and its feasibility for improving the dynamic behaviour of the head actuator is theoretically proved.