• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.859-869
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• 1997

In this paper, the robust design and tolerancing of the stabilized mirror is performed to increase its stabilization performance under vehicle vibration. Based on the sensitivity analysis, the seven important control factors are first identified, and then the optimal as well as robust values in the sense of Taguchi method are obtained. Finally, the tolerances associated with each design variables are determined based on a successive sensitivity analysis of the simulated system response so that the deviation in the response from the target value meets the specification requirements. The proposed tolerancing method features that it is a robust but conservative design method and that the computational effort is much less than the Monte Carlo simulation method.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.109-117
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• 1999

In this paper, a direct adaptive control, based on Lyapunov Function Candidate, is applied to a nonlinear Gunner's Primary Stabilized Head Mirror system to derive a parameter adaptation scheme; furthemore, a nonlinear sliding mode control, but also compensating the error in identification of the parameters which are even varying of have uncertain values. The performance of the adaptive controller is determined by the tracking ability to a desired model under some disturbances and the slowly varying parameters of the system. Both adaptive scheme and sliding mode play an important fole in the improvement of the nonlinear system control.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1332-1335
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• 1996

It is very important to predict the future position for the heavy vehicle with evasive maneuvering. In this paper, we considered for the manual image tracking system. The vehicle images are received from gyro stabilized mirror system, pass through the optical lens, processed, and displayed on the TV monitor. The operator try to lay the reticle to the center of vehicle image. When the vehicle is moving, the mirror platform (actually the line of sight) should follow the vehicle and the angular rate information is picked up from the mirror stabilized system. This rate signal should be used to predict the future vehicle position. The problem is that the visual system of the human operator is in the closed loop system. The rate signals are disturbed by the operator. In addition, there are some non linearities concerned with the control handle bar and the servo control system. The proposed Kalman filter, combined with some modifications for operator disturbance rejection, improved the predication of the future vehicle position when compared with the conventional passive filter used.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.367-370
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• 1991

There are many kinds of drift source in angular velocity feedback stabilization system. We discussed and analyzed the source of drift, and suggest the drift compensation method for null drift system. In this paper, the performance of drift compensators is tested and proved by real 2 axis mirror stabilization system and computer simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.287-291
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• 1995

다구찌 방법을 이용하여 안정거울 시스템의 민감도 해석, 강건설계 및 공차설계를 행하였다. 민감도 해석을 통해 안정거울 시스템의 안정화 성능에 크게 영향을 미치는 7개의 중요한 설계변수를 도출하였다. $m_{M}$이 안정화 성능에 가장 크게 영향을 주므로 공차범위를 줄여야 한다. $m_{M}$, $m_{B}$, $K_{MB}$ , $p_{3}$, $b_{3}$는 공차범위가 크게 안정화 성능에 영향을 미치지 못함을 알 수 있다. 기타의 변수들은 각각 하한공차 및 상한공차로 주어진다.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.4
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• pp.32-41
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• 1994

The stabilized Michelson interferometer was developed in order to measure micro dynamic displacement at the surface of solids due to elastic wave propagation. The stabilizer was designed to compensate light path disturbances using a reference mirror driven by piezoelectric actuator. Using stabilizer, the effect of external vibration was reduced and the quadrature condition was satisifed. As the results, the output of photodetector had maximum sensitivity and linearity. The minimum detectable displacement was 0.3nm at the band width of 10 MHz. The epicentral displacements due to the glass capillary breaks and the steel ball drop impact were measured using the developed interferometer and the results were compared with the calculated one.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.4
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• pp.78-86
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• 2002

In this paper, LMI (Linear Matrix Inequality) based on H$\_$$\infty$/ controller for a lire of sight (LOS) stabilization system. It shows that the proposed controller has more excellent stabilization performance than that of the conventional PI-Lead controller. An H$\_$$\infty$/ control has been also applied to the system for reducing modeling errors and the settling time of the system. The LMI-based H$\_$$\infty$/ controller design is more practical in view of reducing a run-time than Riccati-based H$\_$$\infty$/ controller. This H$\_$$\infty$/ controller is available not only to decrease the gain in PI-Lead control, but also to compensate the identifications for the various uncertain parameters. Therefore, this paper, shows that the proposed LMI-based H$\_$$\infty$/ controller had good disturbance attenuation and reference input tracking performance compared with the control performance of the conventional controller under any real disturbances.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.493-495
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• 1993

The frequency of the 633 nm internal mirror He-Ne laser has been stabilized by using the beat frequency and the intensity difference between two Zeeman split components in a transverse magnetic field. The frequency stability and the frequency temperature coefficient for the beat frequency method was $7.0{\times}10^{-11}$ and $170 kHz/^{\circ}C$, respectively, and those for the intensity difference was $1.1{\times}10^{-9}$ and $1.8 MHz/^{\circ}C$, respectively.

• Journal of Powder Materials
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• v.17 no.3
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• pp.197-202
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• 2010

Low temperature degradation behavior in yttria stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics was microscopically observed from the phase contrast between monoclinic surface and tetragonal matrix. The degradation behavior was dependent on the surface treatment of sintered Y-TZP, even if the sintering history is same. In the mirror polished specimen, the monoclinic layer appeared in a uniform thickness from the surface. On the contrary, for the specimen with coarse scratch, the thickness of degraded surface was more than double especially from the coarse scratch. Since the scratch results in local deformation, the residual stress should be induced around the scratch. With the transformation from tetragonal to monoclinic, the volume expansion exerts a stress on a neighboring grains and promotes a successive phase transformation. Such a autocatalytic effect can be triggered from the part of coarse scratch.

• Current Optics and Photonics
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• v.3 no.6
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• pp.577-582
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• 2019

We report on a continuous-wave (cw) optical parametric oscillator (OPO) optimized for mid-infrared emission above 5.0 ㎛. The OPO is based on a magnesium-oxide-doped periodically poled LiNbO₃(MgO:PPLN) crystal with a fan-out grating design. A linear two-mirror cavity resonating both at the pump and signal wavelengths is stabilized to the pump laser by using the modified Pound-Drever-Hall (PDH) method. The idler wavelength is continuously tunable from 4.7 ㎛ up to 5.3 ㎛ by varying the poling period of the fan-out grating crystal. Pumped by a diode-pumped solid state (DPSS) laser with a power of 1.1 W at 1064 nm, the maximum idler output power is measured to be 5.3 mW at 4.8 ㎛. The output power above 5.0 ㎛ is reduced to the hundreds of ㎼ level due to increased absorption in the crystal, but is stable and strong enough to be measured with a conventional detector.