Gyeonggi do, South Korea
Gyeonggi do, South Korea

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Lim G.,Yonsei University | Park K.-S.,Gachon University | Park N.-C.,Yonsei University | Park Y.-P.,Yonsei University | And 3 more authors.
Microsystem Technologies | Year: 2016

Recently, the number of disks in hard disk drives has increased, and the gap between the slider and disk has decreased. These changes make the contact between the ramp and disk easily. External shock and ramp–disk contact can cause change in disk curvature. Such a change in disk curvature affects the air bearing pressure between the slider and disk. However, disk curvature has not been considered in the previous research. Thus, in this study, we investigated the influence of disk curvature on slider dynamics. Disk curvature was calculated from a transient shock analysis, and was then applied to slider dynamic analysis. As a result, disk curvature reduced the shock performance, by decreasing the minimum flying height and increasing the pitch and roll angle of the slider. © 2015, Springer-Verlag Berlin Heidelberg.


Choi J.,Yonsei University | Park K.-S.,Gachon University | Park N.-C.,Yonsei University | Park Y.-P.,Yonsei University | And 3 more authors.
Microsystem Technologies | Year: 2015

Thermal flying-height control (TFC) technology is now widely applied in the hard disk drive (HDD) industry, because it enables consistent read/write spacing, increases storage density and improves HDD reliability. In a TFC slider, the air bearing pressure at the transducer area can be raised to ten or fifteen times the ambient pressure and it can decrease the air bearing pressure. This paper investigates the effect of humid air condition in TFC slider. It is found that because of the high pressure in transducer area of slider, the water molecules are condensed and the air bearing pressure is changes. Therefore, the slider cannot maintain the flying attitude and the flying-height is changed. Moreover, the change of air pressure causes the change of heat transfer coefficient between slider and air bearing. Consequently, it causes a change of the performance in TFC slider. And in higher humidity and temperature, the effect is intensified. © 2015 Springer-Verlag Berlin Heidelberg


Choi J.,Yonsei University | Park N.-C.,Yonsei University | Park Y.-P.,Yonsei University | Park K.-S.,Gachon University | And 3 more authors.
ASME 2014 Conference on Information Storage and Processing Systems, ISPS 2014 | Year: 2014

This research investigates to analyze the effect of humid air on TFC system. Required parameters of humid air and flying attitude of slider are calculated. Condensation of air bearing at over the saturation vapor pressure is considered. Heat transfer coefficient for humid air condition is calculated. TFC simulation about humid air is conducted. Copyright © 2014 by ASME.


Lim G.,Yonsei University | Park K.-S.,Gachon University | Park N.-C.,Yonsei University | Park Y.-P.,Yonsei University | And 3 more authors.
Microsystem Technologies | Year: 2015

This study investigated the effect of design parameters of a 2.5 inch HDD on the operational shock (op-shock) performance, including the base, cover, ramp stiffness, and the e-block, disk thickness. First, transient shock simulation model was constructed with a nonlinear contact model. From this shock model, the relative displacement between slider and disk is extracted and the vertical force and moment between the slider and disk are calculated. Then, the slider dynamics were analyzed to investigate the characteristics of the head disk interface (HDI) in response to input shock. The input shock is the pulse that is extracted from the transient shock simulation. Finally, the effects of the design parameters on operational shock performance were investigated. © 2015, Springer-Verlag Berlin Heidelberg.


Lim G.,Yonsei University | Park K.-S.,Gachon University | Park N.-C.,Yonsei University | Park Y.-P.,Yonsei University | And 3 more authors.
ASME 2014 Conference on Information Storage and Processing Systems, ISPS 2014 | Year: 2014

This research investigates to analyze the effect of design parameters on operational shock (op-shock) performance. First, op-shock simulation was constructed with a nonlinear contact model and a nonlinear air bearing spring. Then, this simulation was used to investigate the anti-shock performance by design parameters. Copyright © 2014 by ASME.


Lee Y.,Hanyang University | Kim S.H.,Hanyang University | Lee S.-H.,Hanyang University | Lee C.W.,Seagate Korea Design Center | Chung C.C.,Hanyang University
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2014

In this paper, we propose a new control scheme, position and velocity profile tracking control for new generation servo track writing (STW). While conventional servo track writers need controllers that perform fast positioning control with fast track seek and regulation, spiral servo track writers require accurate position and velocity profile tracking control for high quality servo patterns on the media disk. Since STW timing eventually renders geometrically accurate servo patterns, in constant velocity region both position and and velocity error signals should be regulated within small bounds. It is known that regulation via integral sliding mode controller (SMC) provides a good tracking performance, but using a high switching gain is not appropriate for a system having resonance modes. In this paper, thus we apply sliding mode control with disturbance observer to STW. To verify utility of the proposed position/velocity profile track control, we conducted some experiments using a state-of-the-art STW system. Comparative study with the conventional control method was made. The performance of proposed method was experimentally validated. © IFAC.


Lee Y.,Seagate Korea Design Center | Hong E.-J.,Seagate Korea Design Center | Kim C.-S.,Seagate Korea Design Center
IEEE Transactions on Magnetics | Year: 2013

Ramp load/unload (L/UL) technology becomes core technology in mobile hard disk drive (HDD) because it enables higher areal density and stronger shock robustness. However, ramp L/UL has some instability because of the structural limit that a head should repeatedly move between a ramp and a disk. Among much instability, the slider-disk contact generated during L/UL process mainly affects the drive reliability. In particular, the slider-disk contact during the loading process has a critical effect on head-disk interface (HDI) failure due to difference of impact force by much higher height level despite of low frequency. Therefore, this paper mainly focused on the loading contact and instability. At first, we defined the loading contact, scratch and instability generated by the slider-disk contact. To do so, we verified the contact location considering the interaction of the air bearing surface (ABS) and the disk, and we analyzed the relations for the loading contact between the ABS and the slider motions. After definition for the loading contact and instability, we evaluated the effects of the head stack assembly (HSA) height, the ramp height and the disk height based on the ABS performance. The relations among the HSA, ramp, and disk height affected the main parameters related to the loading contact and instability such as the Z-height, the pitch/roll slider attitude, and the gramload. We focused on the effect of the mechanical parameters according to the loading contact and instability. Finally, we measured the height differences for passed and failed drive samples. We could find out how the height differences cause the loading contact and instability through the relation among mechanical parameters such as the height of the HSA, the ramp and the disk. Based on these results, this paper proposed that the mechanical parameters such as the height relations should also be considered in order to avoid the loading contact and instability and to improve the loading performance. © 1965-2012 IEEE.


Park K.-S.,Yonsei University | Lim G.,Yonsei University | Park Y.-P.,Yonsei University | Hong E.-J.,Seagate Korea Design Center | Park N.-C.,Yonsei University
Microsystem Technologies | Year: 2012

Currently, almost all hard disk drives (HDDs) have adopted a loading/unloading mechanism that increases their recording capacity and improves their reliability. However, these mechanisms still create a few scratches or defects in the loading/unloading zone. Slipping at the dimple-flexure interface was recently reported as one of the causes. In this research, we first analyzed the relative behavior of dimple-flexure based on fretting wear marks. We determined that the dimple-flexure behavior included both slipping and rotating motion simultaneously. We then verified the distinct slipping and rolling phenomenon at the moment of ramp contact using finite-element method (FEM) analysis. An experimental setup was constructed, and an unloading experiment was carried out to obtain the ramp contact characteristics corresponding to various unloading velocities. Based on the verified FEM, the characteristics of dimple-flexure relative behavior were investigated for various suspension design parameters, ramp contact characteristics, and unloading velocities. A higher ramp contact force and shorter contact duration resulted in larger slip displacements and roll angles between the dimple and the flexure. Finally, we analyzed the unloading performance of an HDD for various design parameters using quasi-static approximation while considering the relative behavior between the dimple and flexure. The quasi-static analysis indicated a change of approximately 15 % in the flying height at an unloading velocity of 40 in. per second when the relative motion between the dimple and flexure was considered during the unloading process. Even, slider-disk contact occurred at an unloading velocity of 50 ISP. © Springer-Verlag 2012.


Park K.-S.,Yonsei University | Lim S.,Yonsei University | Park Y.-P.,Yonsei University | Chang Y.-B.,Seagate Korea Design Center | Park N.-C.,Yonsei University
Microsystem Technologies | Year: 2012

Hard disk drives (HDDs) in laptop personal computers (PCs) are subject to impact-induced failure, as well as to operational vibrations. Elastic mounts with cushioning materials are often used to minimize the likelihood of failure in such cases. In this paper, we analyze the dynamic characteristics and shock response of the vibration isolation systems supporting HDDs. Anti-vibration performance is investigated via position error signal and acceleration transmissibility. Shock response is obtained from a lumped parameter model, based on the nonlinearity of the rubber mounts. Based on the results, we propose guidelines for shock and vibration isolation systems, including a dual rubber mount design. © Springer-Verlag 2012.

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