• Journal of Institute of Control, Robotics and Systems
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• v.19 no.4
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• pp.285-289
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• 2013

In switching from the track-seeking or track-jumping control mode to track-following control mode in hard disk drives or optical disk drives, initial values of the feedback controller are tuned to improve the transient response. In general, all the initial values of the controller have been compensated for this purpose. In this paper, by partially compensating initial values of digital controllers, we achieve a good performance of the transient response. In the proposed method for IVC (Intial Value Compensation), LMIs (Linear Matrix Inequalities) are used, which includes conditions for improving the performance of the transient response such as reducing a tracking error and control efforts. We obtain optimal initial values of the controller by solving an optimization problem with constraints represented by only one LMI. Although initial values of the controller are partially compensated, we can show that not only a sufficient performance of the transient response is obtained but also control efforts are diminished. The feasibility of the method is verified by simulation studies.

• Transactions of the Society of Information Storage Systems
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• v.11 no.1
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• pp.11-15
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• 2015

In HDD industry, many technologies have been developed and investigated as means to increase the areal density of drives. Thermal flying-height control has been considered and widely applied in current HDD. When contact occur between TFC slider and disk, the slider has a friction heating induced by highly rotated disk. Moreover, because of the friction heating, additional protrusion of slider can occur. The additional protrusion in contact situation can be a severe effect on head part of slider and disk. Therefore, in this paper, we analyze the friction heating and additional protrusion in contact situation.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.6
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• pp.484-491
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• 2005

Using a disturbance observer is effective in enhancing the performance of dynamic system in presence of disturbances. Although various types of disturbance observers have been proposed to improve sensitivity of systems, there exist poor transient responses due to cross-couplings among disturbance observer loops. In this paper, dual disturbance observer (DOB) is proposed to reduce the effects of the cross-couplings. A different type of loop transfer function is proposed for external disturbance observer. While improving the sensitivity function by adding external DOB, it also provides improved complementary sensitivity function. The proposed dual DOB is applied to a commercial optical disk drive tracking system. It is shown that the dual DOB is an effective method in rejecting the effect of disturbance as well as improving the tracking performance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.860-867
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• 2003

This paper presents a systematic method measuring a velocity disturbance to design the robust seek loop system of optical disk drives. The velocity disturbance caused by the rotation of a disk has a greater influence on the performance of the seek control loop as the rotational speed increases. Thus, it needs to measure the extent of the velocity disturbance and design the seek control loop based on the measured data. The measurement method of the velocity disturbance is a real-time . method using a measurable velocity and a velocity controller output and is a robust method considering actuator uncertainties. The loop gain adjustment algorithm is introduced to compensate for the actuator uncertainties. The proposed method is implemented by an experimental digital system and is evaluated through an experiment.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.660-666
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• 2005

Recently, the need for subminiature storage systems has increased with the diversification of portable devices. An actuator for small optical disk drives has to satisfy performance requirements such as higher access speed, lower power consumption, and smaller size. In this paper, we proposed the miniaturized rotary type VCM actuator that had an effective focusing mechanism and secured sufficient bandwidth for small form factor (SFF) optical disk drive (ODD). Initial model was designed by electromagnetic (EM) and structural analyses. Such a model was improved using design of experiments (DOE) procedure based on a Blu-ray disk (BD) 1x specifications.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1004-1009
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• 2002

There are four servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is conventional and the other is newly developed. Focus error signal between lens and disk is detected using LDV 2 beam method. The system is observable and all states are estimated. Full states feedback controller and minimum order observed are designed using those states. Impulse responses are simulated. And experiment is performed to compare with responses of conventional model.

• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.397.2-397
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• 2002

There are 4 servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is newly developed and the other is conventional. Focus error signal between lens and disk is detected using LDV 2 beam method. (omitted)