Study on flow-induced vibration of head–disk assembly mechanisms in actual hard disk drive

Abstract

Achieving ultra-high magnetic-recording density in hard disk drives (HDDs) requires clarification of flow-induced vibration issues. In particular, it is necessary to reduce the flow-induced disk vibration called disk flutter. Thus far, however, there has been no experimental research related to disk flutter in actual HDDs. For this study, therefore, the disk-flutter issues have been studied experimentally, using an actual 2.5-in. HDD with one disk and two magnetic heads. The aim was to study the effect of operating magnetic-head mechanisms on flow-induced disk flutter. This study evaluated disk flutter as well as static pressure distribution in the actual HDD, by taking measurements while changing the operating modes of the magnetichead mechanism as well as the number of operating air-bearing sliders. The study demonstrated that the disk-flutter amplitude increases and its frequency decreases when the magnetic-head mechanisms are operating. It was also found that the amount of decrease in the disk-flutter frequency depends on the number of operating air-bearing sliders whose amplitude increase varies with the specific operating mode of the head mechanisms, such as whether it is in trackfollowing or seek modes. In addition, operation of the magnetic-head mechanisms generated non-uniform static pressure distribution within the HDD. These factors suggest that a decrease in disk-flutter frequency results from the slider-coupled vibration and an increase in disk-flutter amplitude results from the static pressure changes as well as air-following changes, as these vary with the actual operation of the disk head mechanism. From these experimental results, it appears that the disk-flutter issues in actual HDDs should be considered as a system that includes the operation of the magnetic-head mechanisms and disk-coupled vibration.

Improvement of Convergence for Adaptive Feed-Forward Cancellation Using Variable Gains in a Head Positioning System of Hard Disk Drives

“…Disk flutter occurs due to the disk mode shape caused by airflow (9) (12) . The notation for disk flutter mode is (m, n), where m is the number of nodal circles and n is the number of nodal diameters.…”

“…The amplitude gradually increases as the magnetic head moves towards the inner side of the disk. On the other hand, disk flutter occurs due to the disk mode shape (9) . The amplitude gradually increases as the magnetic head moves toward the outer side of the disk.…”

Aerodynamic Pressure Fluctuations Associated With Flow-Induced Vibration of the Head Gimbals Assembly Inside a Hard Disk Drive

“…The FIV characteristics of an HGA with different operation modes in an HDD has been investigated experimentally with a laser Doppler vibrometer in vibration detection [11]. Furthermore, large eddy simulation (LES) [6], [12], [13] or direct numerical simulation [14] technique has been employed for detailed investigation on the unsteady flow behavior and FIV mechanism inside an HDD. In these studies, however, not much results have been reported on the turbulent flow fluctuations inside HDDs, which shall be the direct aerodynamic excitation for the FIV in HDDs.…”