• Transactions of the Society of Information Storage Systems
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• v.3 no.1
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• pp.5-12
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• 2007

This paper investigates the design of disturbance observer for rotational vibration suppression in disk drive systems. The design aims to provide an optimal controller which satisfies both vibration performance and robust stability. It consists of an inversion method, a special filter, and optimization scheme. Firstly a new inversion method is introduced, which provides more accurate inversion compared to conventional zero phase error method. The inversion is to deal with unstable zeros in the plant model. Secondly a special filter for disturbance selection is given, which features adjustable gain and band pass characteristics so that it enables flexible shaping of the loop considering the trade-off between performance and stability margins. And finally the parameters of disturbance observer are optimized in conjunction with external disturbance model. Simulation and experiment on commercial hard disk drives confirm that the design is very effective to such disturbance which is hard to be handled by conventional approach.

• Journal of KSNVE
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• v.11 no.3
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• pp.449-454
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• 2001

The shock performance of hard disk drives has been a serious issue for portable computers and AV application HDD. Focusing on the motion of an actuator, we investigated non-operational shock mechanism and studied several parameters that affect the shock performance by experimental analysis. It was found that there are two important factors fort the actuator to endure high shock revel. One is a shock transmissibility and the other is a beating between the arm blade and the suspension. To generalize the shock transmissibility, the concept of shock response spectrum was introduced. The shock response spectrum of the actuator system was obtained experimentally and compared with that of an analytical single degree of freedom model. It was found that there was a good agreement. The first bending natural frequency of the arm blade was found to be the most important factor for the low shock transmissibility. By applying the shock response spectrum and avoiding the beating, we could design an actuator of high shock performance.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.46-51
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• 2009

Recently, the shock resistance and dynamic characteristics of hard disk drives have become more important due to their highly increased storage density and miniaturization. In this study, we have developed an ANSYS/Mechanical/LS-DYNA based HDD vibration/shock simulation tool for design engineers. This simulation tool using ANSYS APDL can produce a parametric finite element modeling of HDD automatically and has GUI-based applications using the script program language Tcl/Tk. In the present tool, we adopt the reliable methodology of vibration/shock simulation, which is experimentally verified. It is expected that this simulation tool can make the repetitive computational efforts for the shock-proof design of HDD drastically reduced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1545-1551
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• 2002

The optical storage device has recently experienced significant improvement, especially for the aspects of high capacity and fast transfer rate. However, it is necessary to study a new shape of air bearing surface for the rotary type actuator because the optical storage device has the lower access time than that of HDD (Hard Disk Drives). In this study, we proposed the air bearing shape by using SA (Simulated Annealing) algorithm which is very effective to achieve the global optimum instead of many local optimums. The objective of optimization is to minimize the deviation in flying height from a target value 100nm. In addition, the pitch and roll angle should be maintained within the operation limits.

• Transactions of the Society of Information Storage Systems
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• v.3 no.4
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• pp.183-190
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• 2007

In most hard disk drives that apply the ramp load/unload technology, the head is unloaded at the outer edge of the disk while the disk is rotating. During the unloading process, slider-disk contacts may occur by lift-off force and rebound of the slider. The main issue of this paper is to prevent the slider-disk contact by rebound, and we apply a disk bump to the unloading process. To do so, first, the ranges of bump dimension are determined. Second, the stability of each bump is checked by dynamic simulation. Finally, unload simulations are performed for stable bump designs. As a result of these steps, the effect of the bump design and the position for the unloading performance were investigated. As a consequence, we propose the optimal bump design to improve the unloading performance. Furthermore, we can identify to remove rebound contact by applying a bump on disk during the unloading process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.926-929
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• 2000

As the track density of hard disk drives increases, there is a need for more precise actuation of the head. This can be accomplished by using a high band width micro-actuator. In this work, the flying characteristics of sliders with micro-actuators are investigated with the aim to optimize the head/disk interface performance of such sliders. Contact-start-stop, sweep, and flying height tests are performed and analyzed. The results show that the MEMS based micro-actuator mounted on a slider possess acceptable flying characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.96-100
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• 2001

As the track density of hard disk drives increases, there is a need for more precise actuation of the head. This can be accomplished by using a high band width micro-actuator. In this work, the flying characteristics of sliders with micro-actuators are investigated with the aim to optimize the head/disk interface performance of such sliders. Contact-start-stop, sweep, and flying height tests are performed and analyzed. The results show that the MEMS based micro-actuator mounted on a slider possess acceptable flying characteristics.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.663-666
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• 2002

Hard disk drived (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. The distribution of pressure disturbance on disks has relation to flow structure. To investigate the flow structure, time-resolved hot-wire measurements of the circumferential velocity component were obtained for the flow between the center pair of four disks of common radius $R_2$ coretating at angular velocity ${\Omega}$ in a fixed cylindrical enclosure. Hot-wire supporter acts as an obstruction in this case. The effects of rotating speed and size of hot-wire supporter diameter between disks on the flow driven by disks were investigated. Velocity spectra at the fixed space were measured to obtain the structure of inner and outer region in flow field.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.242-245
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• 2005

The rotating flow in the space between co-rotating disks is of considerable importance in information storage systems. Hard disk drivers(HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speed requires an improved understanding of fluid motion in the space between disks. In this study, we have tried LES model for inner-disk flowfield to investigate the flow disturbance and the flow structure driven by co-rotating disks. The boundary pattern between inner region and outer region obtained lobe-shape structure clearly and its number has been validated on experimental data by our previous study. We obtain the spectra of velocity and pressure components with several frequencies. We revealed there are two kinds of disturbances, one is global wave propagation and another is local wave propagation on Ekman boundary layer.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.695-701
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• 1995

Fundamental issues and general procedures of modeling the head disk interface (HDI) in order to provide design criteria for future ultra-low flying sliders are given. Intermittent contact and gaseous rarefaction effects are discussed using nonconventional kinetic theory. To illustrate the simulation results, we modeled IBM 3370 taper flat sliders and positive/negative "bow tie" sliders. Several alternative HDI concepts for future disk drives - viscoelastic bearings, a hybrid system, and contact recording - are also briefly discussed.