• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.742-747
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• 2000

The optical storage device has recently experienced significant improvements, especially for the aspects of high capacity and fast transfer rate. However, it is the fact that the optical storage device has the lower access time for the randomly scattered data compared to the hard disk drives. It is, therefore, necessary to develop a new type of optical storage system. In this study, we investigate the air bearing characteristics for the optical disk drives which have the swing arm actuator similarly to the hard disk drives. Considering the requirements of the optical disk drives, we parametrize the shape of the air bearing surface and investigate its sensitivity to the flying characteristics for further optimized design outputs.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.101-105
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• 2006

Disk radial runout creates a periodic relative motion between the laser beam spot and tracks formed on an optical disk. While only focus control is activated, the periodic relative motion yields sinusoid-like waves in the tracking error signal, where one cycle of the sinusoid-like waves corresponds to one track. The frequency of the sinusoid-like waves varies depending on the disk rotational speed and the amount of the disk radial runout. If the frequency of the tracking error signal in the off-track state is too high due to large radial runout of the disk, it is not a simple matter to begin track-following control stably. It might take a long time to reach a steady state or tracking control might fail to reach a stable steady state in the worst case. This article proposes a simple method for reducing the relative motion caused by the disk radial runout in the off-track state. The relative motion in the off-track state is effectively reduced by a drive input obtained through measurements of the tracking error signal and simple calculations based on the measurements, which helps reduce the transient response time of the track-following control. The validity of the proposed method is verified through an experiment using an optical disk drive.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.5
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• pp.598-603
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• 2004

An optical head actuator of an optical disk drive consists of two servo mechanisms for the focusing and the tracking to acquire data from disk. As the rotational speed of the disk grows, the utilized lag-lead-lead compensator has known to be above its ability for precisely controlling the optical head actuator. To overcome the difficulty, this paper propose a new controller design method for optical head actuator based fuzzy proportional-integral-derivative (PID) control and the genetic algorithm(GA). It employs a two-stage control structure with a fuzzy PI and a fuzzy PD control and is optimized by the GA to yield the suboptimal fuzzy PID control performance. It is shown the feasibility of the proposed method through a numerical tracking actuator simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2092-2099
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• 2013

Through the data transfer race in industry since 1990s, the operational speed of optical disk drive(ODD) becomes commonly over 10,000 rpm. Such high speed operation inevitably causes the vibration, which is also the disturbances in the read-write process of pick-up servo-controller. Generally the vibration disturbance problem can be solved by the vibration isolation using the rubber mount and the increase of robustness of the pick-up servo-controller. Optical disk itself has not been targeted for the vibration reduction, because it is manufactured under the standardized format. In this paper we focused on the increase of critical speed of optical disk, that is, the improvement of dynamic characteristics, with the control of residual stresses which are come from the injection molding process. To do this, first, the residual stresses induced from the injection molding process are calculated using finite element method. The major design parameters of the process conditions are flow rate and melt temperature, which control the residual stresses in optical disk. Second, the critical speed of optical disk is calculated with modal analysis considering residual stress distributions. It was found out that the critical speed can be improved by the control of operational parameters in the injection molding process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.867-870
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• 2002

In high-speed optical disk drive, the excitation caused by rotation of a mass-unbalanced disk is a major source of vibration. The vibration can be a disturbance to the servo system, which is sufficient to cause severe failures in the reading and writing process. The vibration also causes users to feel unpleasantness. The vibration reduction is therefore essential for the reliable operation of optical disk drive. One of the approaches to reduce the vibration is a dynamic vibration absorber (DVA). In this paper, we analyze the dynamic behavior of $DVD\pmRW$ combo drive system with DVA through 12_dof rigid multi-body dynamic model. The effective location and the optimal frequency ratio are obtained from the analysis.

• Transactions of the Society of Information Storage Systems
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• v.2 no.3
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• pp.201-207
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• 2006

Information storage devices have been studied to increase the storage capacity and the data transfer rate as well as to decrease the access time and their physical sizes. Optical information storage devices have been achieved high-capacity by reducing optical spot size remarkably due to the development of Blue-ray technology. Optical information storage devices usually use 1.2mm-thick polycarbonate(PC) media to get high enough stiffness. However, it would be better if we can decrease the thickness of a disk for achieving thinner device while keeping the capacity as large as possible. Decreasing the thickness of the storage media makes it difficult to read and write data because it increases the transverse vibration of the rotating disk due to the interaction with surrounding air and the vibration characteristics of thin flexible disk itself, Therefore, a special design based on the fluid mechanics is required to suppress the transverse vibration of the disk in non-contact manner so that the optical pickup can read/write data successfully. In this study, a curved wall is proposed as a stabilizer to suppress the transverse vibration of a $95{\mu}m$-thick PC disk. The characteristics of disk vibration due to a curved wall have been studied through numerical and experimental analysis from the fluid mechanics point of view. The proposed shapes are possible candidates as stabilizers to suppress the transverse vibration of a flexible disk which rotates at high speed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.397-400
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• 2000

The demands of high data transfer rate and high recording density in optical disk memory device are being increased. In order to achieve high performance, lever actuator for optical disk is proposed. Firstly, the role of lever and structure are discussed and the flexure hinge is introduced to enhance the precise movement. Next is to present the magnetic circuit structure and concept design for the lever actuator. Finally, the dynamic modeling of the lever actuator is found and the analysis results are shown. Consequently, the lever actuator shows the possibility as a pickup actuator for the next generation optical disk.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.661-667
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• 2002

With the increase of storage density, high rotational speed and high access technologies in optical disk drive, mechanical issues, mainly noise and vibration, become critical. Up to now the researches of rubber mount for anti-vibration focused on how to calculate the static and the dynamic stiffness of rubber mount and loaned out consideration of the dimensional tolerance of rubber mount for anti-vibration. This paper presents the effects of dimensional tolerance of rubber mount for anti-nitration on the dynamic characteristics of optical disk drive by finite element analysis and dynamic test. The relation between dimensional tolerance and dynamic characteristics of optical disk drive is observed and discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.622-625
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• 2008

SIL-based optical disk drive will be promising candidate of next-generation storage devices. However, a near-field optical disk drive requires the robustness to external shock because of extremely small gap between SIL and media. Especially, high-level shock damages permanently to SIL and it makes difficulties in general application. To study the likelihood of failure, the shock analysis must be performed over all others. This research explores the dynamic characteristics of rotating disk through FEM which is compared to analytical solution and experimental modal analysis. We also develop the finite element model of an optical disk drive, which includes rubber mounts, sled base, rotating disk and pickup assembly, and simulate the shock response.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.80-83
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• 2003

Transcribability of pit or land groove structures in replicating an optical disk substrate greatly affects the performance of a high-density optical disk. However, a solidified layer, generated during the polymer filling, deteriorates transcribability because the solidified layer prevents the polymer melt in filling the sub-micro patterns. Therefore, the development of the solidified layer during filling stage of injection molding must be delayed. For this delay, passive heating by insulation layer has been used. In the present study, to examine the development of the solidified layer delayed by passive heating, the flow of polymer melt with passive heating was analyzed. Passive heating markedly delayed the development of the solidified layer, reduced the viscosity of the polymer melt, and increased the fluidity of the polymer melt in the vicinity of the stamper surface with the sub-micro patterns. As a result, we predict that passive heating can improve transcribability of an optical disk substrate. To verify our prediction, we fabricated an optical disk substrate by using passive heating of a mold and measured the transcribability.