• Tribology and Lubricants
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• v.23 no.4
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• pp.175-179
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• 2007

The effect of manufacturing parameters on friction characteristics of motorcycle break system was studied using a design of experiment. Such parameters conditions have an effect on the frictional factor such as applied load, sliding speed, and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factors. In this study, the friction characteristics using design of experiment containing 3 elements were investigated for an optimal condition for the best motorcycle break system employing full factorial design. From this study, the result was shown that the applied load in frictional factors was the most important, next to sliding speed, number of ventilated disk hole.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.10 s.103
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• pp.1148-1159
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• 2005

In this paper, the various uncertainties generated in an optical disk drive (ODD) and the robust servo designs considering the uncertainties are studied. First, the brief introduction an ODD and the servo error tolerance of it are discussed. Then, the classifications of uncertainty and the concept of relative stability are introduced. Considering the uncertainty of an ODD, two robust control approaches are applied: (i) mixed sensitivity approach in H$\infty$ control theory for unstructured uncertainty, (ii) QFT for structured uncertainty Finally, the designed controllers are realized by DSP, and these controllers are applied to a commercial DVD-ROM drive. From these experiments, we prove that the designed robust controllers have more good disturbance rejection performance and robustness when it is compared to the conventional lead-lag controller.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.196-202
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• 2002

In this work, we propose a new type of HDD suspension featuring shape memory alloy (SMA) actuator in order to prevent the contact between the slider and disk. The principal design parameters are obtained from the modal analysis using finite element analysis, and then the dynamic model is established to formulate the control scheme for Non-Contact Start/stop mode drive. Subsequently, a robust H$\_$$\infty$/ control algorithm is designed by integrating experimentally-Obtained SMA actuator dynamics to the proposed HDD suspension system. The controller is empirically realized and control results for the load/unload profiles are presented in time domain. In addition, the contact signal between the slider and disk is measured by the electrical resistance method.

• Transactions of the Society of Information Storage Systems
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• v.2 no.4
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• pp.240-244
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• 2006

As high-definition television(HDTV) broadcasting becoming more generalized, there have been many researches and developments about a large storage capacity and a fast data transfer rate in optical disk drives (ODD). Pickup actuators must have high flexible mode frequencies and large gain margins. Flexible modes are caused by the flexibility of moving parts in the actuator and a servo bandwidth is limited by them. As a result, the system becomes unstable for high-speed operations in high density reading and recording. In this paper, we suggest improved modeling method in considering of the bonding layer. And, the flexible mode frequency of actuator is improved by Design of Experiments of lens holder. The Magnet circuit is designed considering the relation with the moving part. Through improving the yoke design, the magnetic flux is changed and the DC tilt is reduced. Consequently, we designed an actuator which has a high flexible mode frequency and a large gain margins.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1132-1138
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• 2005

Recently, production and use of freon substances are restrained due to depletion of ozone layer and global warming. In this aspect of environmental problems, the best solution is to use the natural refrigerant such as ammonia. Thus, this study is to find the optimal operating conditions by comparing the performance between the shell and tube type and shell and disk type heat exchangers using the ammonia refrigerant, and to verify the superiority of the shell and disk type heat exchanger that is not used in field of refrigeration and air conditioning. Finally, this study shows that the shell and disk type heat exchanger is applicable to the ammonia refrigeration system, and this system minimizes the refrigerant charge and installation space.

• The Bulletin of The Korean Astronomical Society
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• v.15
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• pp.13.1-13.1
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• 1990

• The Bulletin of The Korean Astronomical Society
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• v.24 no.2
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• pp.100-100
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• 1999

• The Bulletin of The Korean Astronomical Society
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• v.18
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• pp.26-27
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• 1993

• The Bulletin of The Korean Astronomical Society
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• v.18
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• pp.27.1-27.1
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• 1993

• The Magazine of the IEIE
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• v.37 no.3
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• pp.51-60
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• 2010