• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.115-126
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• 1996

In the time optimal control problem, bang-bang control has been used becaese it is the theoretical time minimum solution. However, to improve tracking speed performance in the time optimal control, it is important to select a switching point accurately which makes the velocity zero near the target track. But it is not easy to select the swiching point accurately because of the damping coefficient variation and uncertainties of modeling an actual system. The Adaptive model following control(AMFC) is implemented to relieve the difficulty and inconvenience of this task. The AMFC and make the controlled plant follow as closely as possible to a desired reference model whose switching point can be calculated easily and accurately, assuring the error between the states of the reference model and those of the controlled plant appoaches zero. The hybrid control method composed of AMFC and PID is applied to a tracking actuator of the magneto optical disk drive(MODD) in random access devices to improve its slow tracking performance. According to the simulaion and experimental results, the average tracking time as small as 20ms is obtained for a 3.5 magneto-optical disk drive. The AMFC also can be applied for other random access devices to improve the average tracking performance.

• Proceedings of the Korean Magnestics Society Conference
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• 1994.03a
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• pp.12-13
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• 1994

Magnetic recording is still considered to be a.leader in storage industries in general. The rigid disk drive, in particular, has an advantage over tape, optical, magneto-optical, or flash memories, because of high areal density and fast access time with reasonably low cost per Mbyte. However, to be competitive in the market and to keep an edge over other storage devices, head and media in rigid disk drives require better performance per cost and more aggressive improvement in areal density, as shown in Fig. 1, than before. In this review paper, the future trend in head/media technologies of the rigid disk drive has been reviewed. Thin film media and thin film inductive/MR heads will be mainly discussed, since they are expected to be dominant in the future high-end drives over other technologies, such as particulate media or MIG heads.(omitted)mitted)

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.296-297
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• 2003

사회의 정보화가 급속하게 진전됨에 따라 취급해야 할 데이터 양이 증가되면서 정보 저장장치의 고속화, 소형화, 및 대용량화의 필요성이 대두되고 있다. 많은 양의 데이터를 저장하기 위해서는 저장장치의 물리적 디스크 공간이 높은 기록밀도를 가져야 한다. 이를 위한 방법으로 하드디스크 기술과 광자기 디스크 장치(magneto-optical disk drive) 기술을 결합하는 근접장 복합 기록 방법(Near field hybrid recording method)들이 보고 되었다. (중략)

• Journal of the Korean Magnetics Society
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• v.6 no.3
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• pp.174-178
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• 1996

A method was studied which simulate signal and noise for magneto-optical disk drive system Recorded mark patterns and incident laser beam were modeled and discretized. Using them readout waveformj and amplitude were simulated. Adding Gaussian random noise to the readout signal and executing one dimensional discrete FFT (Fast Fourier Transform) algorithm signal and noise spectrum was estimated. From the spectrum, CNR (Carrier to Noise Ratio) was obtained.

• 한국해양학회지
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• v.27 no.1
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• pp.19-34
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• 1992

Marine seismic refraction surveys have been carried out by Korea Institute of Geology, Mining and Materials(KIGAM) since 1984. The recording of refraction data was based on analog instrumentation. Therefore the resolution of refraction data was not good enough to distinguish many layers. The objective of the interpretation of seismic refraction data is the determination of intervals and critically refracted seismic wave propagation velocities through the layers beneath the sea floor. To determine intervals and velocities precisely, the resolution of refraction data should be enhanced. The intent of the study is to improve the quality of shallow marine refraction data by the digital technique using microcomputer- based acquisition and processing system. The system consists of an IBM AT microcomputer clone, an analog-digital(A/D) converter. A mass storage unit and a parallel processing board. The A/D converter has 12 bits of precision and 250 kHz of conversion rate. The magneto-optical disk drive is used for the mass storage of seismic refraction data. Shallow marine seismic refraction surveys have been carried out using the system at 6 locations off Ulsan and Pusan area. The refraction data were acquired by the radio sonobuoy. The refraction profiles have been produced by the laser printer with 300 dpi resolution after the basic computer processing. 5-9 layers were interpreted from digital refraction profiles, whereas 2-4 layers were interpreted from analog refraction profiles. the propagation velocities of sediments were interpreted as 1.6-2.1 km/sec. The propagation velocities of acoustic basement were interpreted as 2.4-2.7 km/sec off Ulsan area, 4.8 km/sec off Pusan area.