• 스마트미디어저널
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• 제4권2호
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• pp.62-67
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• 2015

Hard disk drive(HDD)는 보조 저장장치로서 대부분의 컴퓨터 시스템에서 사용되고 있으나 기계적 특성으로 인하여 성능의 향상 측면에서는 한계점에 도달해 있는 상황이다. 반면, 플래시 메모리 기반인 solid state drive(SSD)는 고성능 저소음이라는 장점이 있지만, HDD에 비해 높은 가격으로 인해 아직 HDD를 완전 대체하기에는 부담이 크다. 따라서 SSD를 대용량인 HDD의 cache로 사용하는 SSD caching mechanism이 최근 주목을 받고 있다. SSD caching mechanism은 대표적으로 bcache, dm-cache, Flashcache, EnhanceIO 등이 있으며, 각 mechanism들은 구현상의 장단점과 차별성이 존재한다. 본 논문에서는 각 SSD caching mechanism들의 특정을 파악하고, 벤치마크를 통하여 성능을 비교 분석하였다. 이러한 연구를 기반으로 향후 더 성능이 좋은 SSD caching mechanism을 개발하는데 기여할 수 있을 것으로 예상된다.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권10호
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• pp.671-677
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• 2004

This paper presents the design of a now controller for the read/write head of a hard disk drive. The general controller for seeking is the time-optimal control. However if we use only the time optimal control law, this could be vulnerable to chattering effect. To solve this problem, we propose a modified controller design algorithm in this paper. The proposed controller consists of bang-bang control for seeking and sliding-mode control for tracking. Moreover, to test the robustness and stability of control system, a bounded disturbance is selected to maximize a severity index. Simulation results show the superiority of the proposed controller through comparison with time optimal VSC(variable structure control).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.993-993
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• 2014

Increasing the density magnetic recording of a hard disk drive needs to improve position control of a slider. We have troubles analyzing position of a slider by nonlinear property of pivot ball bearing. Many researches analyze a hard disk drive to change pivot ball bearing part from balls to springs. Pivot ball bearing operates by rotation and movement of balls. This study considers Hertzian contact force when balls contact with outer race to analyze nonlinear movement of a ball bearing. Experiment of this study measures movement of a circular center of a pivot ball bearing. We also verify the simulation results and the experiment results.

• 정보저장시스템학회논문집
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• 제9권2호
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• pp.51-55
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• 2013

HDD has been easily exposed to the external shock and vibration because HDD has to apply to mobile devices. Therefore, the stiffness of base has been the important factors for the design of HDD. To improve the stiffness of base, the frame was applied to the base. First, the finite element model of the base was constructed. Then, the FE model was verified by modal analysis. Drop test was performed to confirming the shock simulation model. The dynamic characteristic of original base which is verified is compared with the base which is applied the frame through modal analysis and shock analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1272-1275
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• 2007

The HDD (hard disk drive) using Load/Unload (L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop (CSS). Dynamic L/UL has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. Main design objectives of the L/UL mechanisms are no slider-disk contact or no media damage even with contact during L/UL, and a smooth and short load and unload process. In this paper, we focus on state matrix, pitch static attitude (PSA), roll static attitude (RSA), loading/unloading contour (LC/ULC), impact force and contact. Stability of slider is mainly determined by PSA and RSA. State matrix by PSA and RSA is also important indicator. Therefore we analyze state matrix of SFF HDD suspension through the LC/ULC.

• 정보저장시스템학회논문집
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• 제2권1호
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• pp.32-37
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• 2006

The recording density of a hard disk drive(HDD) has been increased so rapidly that the storage capacity of a commercial HDD for the personal computer already reaches several hundred giga-bytes recently. Many technologies related to the HDD, such as servo, media, actuator dynamics, thermo and fluid dynamics, etc. must be developed together to realize higher recording density. Especially, airflow inside the HDD cavity has been concerned as the rotational speed of the disk increases. Typical problem due to the airflow is the off-track vibration of a head stack assembly(HSA) as the airflow collides with the E-block, suspensions, and sliders, i.e., the flow induced vibration(FIV). This problem is one of the most significant sources of the track mis-registration(TMR) so that it must be resolved. In this study, disk damper shape is modified to minimize the influence of airflow on the HSA. Modified disk dampers, which change the flow field of the inside cavity of a HDD, show good effects not only on the disk vibration but also on the off-track vibration of a HSA. Vibrations of E-block and slider have been measured with LDV and the airflow field inside the HDD cavity has been analyzed with commercial CFD program to verify these effects.

• 한국소음진동공학회논문집
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• 제16권1호
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• pp.12-18
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• 2006

This research investigates the electromechanical characteristics of a spindle motor in a free-falling mobile hard disk drive before unexpected shock. Electromechanical simulation includes a time-stepping finite element analysis of the magnetic field in a speed controlled brushless DC motor and dynamic analysis of the stationary and rotating part linked by the fluid dynamic bearing under the free-falling condition. Analysis results show that the dynamic characteristics of the rotating spindle system during free-falling state have an effect on the relative motion between the stationary and rotating part of HDD. It results from the variation of reaction force in the bearing area due to the gravity force exerted on the rotating part of HDD, and the free-falling condition can be detected by observing the signal of the spindle motor and disk-head interface without using an accelerometer.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.324-329
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• 2005

This research investigates the electromechanical characteristics of a spindle motor in a free-falling mobile hard disk drive before unexpected shock. Electromechanical simulation includes a time-stepping finite element analysis of the magnetic field in a speed controlled brushless DC motor and dynamic analysis of the stationary and rotating part linked by fluid dynamic bearing under the free-failing condition. Analysis results show that the dynamic characteristics of the rotating spindle system during free-falling state have an effect on the relative motion between the stationary and rotating part of HDD. It results from the variation of reaction force in the bearing area due to the gravely force exerted on the rotating part of HDD, and the free-failing condition can be detected by observing the signal of the spindle motor and disk-head interface without using the accelerometer.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.319.1-319
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• 2002

A frequency-domain PES estimation and its prediction method are proposed for the tightly-coupled servo/mechanical design of high-TPI HDD system above 100kTPI. The major two disturbance energies which are related with mechanical vibrations inside of HDD are used to predict the drive-level PES, while considering closed-loop servo dynamics. One is the torque disturbance which mainly comes from aerodynamic excitation of HSA system and the other is the displacement disturbance from disk-spindle dynamics. (omitted)

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.664-669
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• 2003

Recently, the recording density of hard disk drives has improved at an annual percentage rate of 100%. Therefore for faster access, higher disk rotational speeds will be required. The influence of the airflow produced by the rotation of a disk on the positioning accuracy has become a serious topic of research and the aerodynamic aspect of hard disk drives is now quite considerable with the increases in recording density and higher rotational speeds. Unsteady airflow in an actual hard disk drive is numerically simulated by using LES(Large Eddy Simulation) technique, we could predicted and aerodynamic mechanism that was related actuators' surroundings in HDD. At a result, with modifying the various shapes of the E-block and Damper, we estimated the characteristic of the influence of airflow in HDDs.