• Title/Summary/Keyword: Q-Switched

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HIERARCHICAL SWITCHING CONTROL OF LONGITUDINAL ACCELERATION WITH LARGE UNCERTAINTIES

  • Gao, F.;Li, K.Q.
    • International Journal of Automotive Technology
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    • v.8 no.3
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    • pp.351-359
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    • 2007
  • In this study, a hierarchical switching control scheme based on robust control theory is proposed for tracking control of vehicle longitudinal acceleration in the presence of large uncertainties. A model set consisting of four multiplicative-uncertainty models is set up, and its corresponding controller set is designed by the LMI approach, which can ensures the robust performance of the closed loop system under arbitray switching. Based on the model set and the controller set, a switching index function by estimating the system gain of the uncertainties between the plant and the nominal model is designed to determine when and which controller should be switched into the closed loop. After theoretical analyses, experiments have also been carried out to validate the proposed control algorithm. The results show that the control system has good performance of robust stability and tracking ability in the presence of large uncertainties. The response time is smaller than 1.5s and the max tracking error is about $0.05\;m/S^2$ with the step input.

A Study on the Passive Modelocking of Ring Type Er-doped Fiber laser (고리형 어븀첨가 광섬유 레이저의 수동형 모드로킹에 관한 연구)

  • 한두희
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.1 no.2
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    • pp.63-68
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    • 2000
  • A passively mode-locked ring type fiber laser had been installed in order to get the short pulses The single and the double mode-locking were appeared, and the shortest pulse length of 65 fs was obtained with a 110 m long dispersion shifted fiber(DSF) in a local cavity of 139.8 m. Also high order harmonic modelocking of 17th and Q-switched high order harmonic modelocking were obtained.

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Design of a Continuous-Time Filter Using the Modified Chebyshev Function and DDA (개선된 Chebyshev 함수와 DDA를 이용한 연속시간 필터 설계)

  • 최석우;윤창훈;김동용
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.32B no.12
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    • pp.1572-1580
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    • 1995
  • In this paper, a modified Chebyshev low-pass filter function is proposed. The modified Chebyshev filter function exhibits ripples diminishing toward .omega. = 0 in the passband. So, the modified filter function is realizable in the passive doubly-terminated ladder network for the order n even or odd, thus lending itself amenable to active RC or switched capacitor filters through the simulation techniques. Besides the passive doubly-terminated ladder realizability, lower pole-Q values of the modified function are accountable for improved phase and delay characteristics, as compared to classical function. We have designed the 6th order passive doubly-terminated network using the modified function. And then a continuous-time DDA(Differential Difference Amplifier) filter, which has no matching requirement, is realized by leap-frog simulation technique for fabrication. In the HSPICE simulation results, we confirmed that the designed continuous-time DDA filter characteristics are agreement with the passive filter.

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Self-starting phase conjugate laser in population inverted Nd:YAG (밀도 반전된 Nd:YAG에서의 자체 발진 위상공액 레이저)

  • ;M.J.Damzen
    • Korean Journal of Optics and Photonics
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    • v.8 no.5
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    • pp.357-361
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    • 1997
  • We report the operation of a self-starting phase conjugate laser(PCL) oscillator which compensates intracavity phase distortion. The self-starting PCL in the population inverted Nd:YAG gain media produced an output energy of 200 mJ in a 20 ns single-longitudinal-mode pulse at 10Hz. And it showed well-defined Gaussian spatial profile.

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Nano-Second Periodically Poled Lithium Niobate Optical Parametric Oscillator with Planar Cavity Mirrors

  • Kim, Hong-Ki;Rhee, Bum--Ku
    • Journal of the Optical Society of Korea
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    • v.5 no.4
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    • pp.136-139
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    • 2001
  • We investigated a high-output ower, periodically poled lithium niobate(PPLN) optical parametric oscillator(OPO) pumped by a Q-switched Nd:YAG laser. Given the low optical damage threshold and the limited aperture (0.5mm thick) of PPLN, we tried to maximize the signal output power in a linear cavity consisting of two flat mirrors with a loosely focused pump beam. It is found that this simple cavity structure allowed a robust OPO operation, which was not sensitive to alignment compared with the conventional ones using concave mirrors. A maximum energy of 100$\mu$J/pulse was achieved for the signal at 1.36${\mu}{\textrm}{m}$, while the oscillation threshold was 0.3 mJ/pulse for the pump at 1064 nm.

Detection of Damage of Rd6G Film Using Surface Second-Harmonic Generation (표면 제2고조파 발생을 이용한 색소 Rd6G박막층의 손상 분석)

  • 유대혁;고춘수;임용식;이재형;장준성
    • Korean Journal of Optics and Photonics
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    • v.5 no.2
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    • pp.272-277
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    • 1994
  • The damage of a thin film of Rd6G dye was probed by Surface Second-Harmonic Generation(SSHG) method. A portion of the Rd6G thin film on glass substrate was damaged by 532 nm laser beam, and the damage was probed by detecting intensity variation of SSHG. The result was confirmed through direct observation with optical microscope.oscope.

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Bonding and Physical Characteristics of Diamond-like Carbon Films Prepared by Laser Ablation (레이저 어블레이션에 의해 증착된 비정질 다이아몬드 박막의 결합및 물리적 특성)

  • Park, Hwan-Tae;Hong, Young-Kyu;Kim, Jae-Ki;Kim, Jin-Seung;Park, Chan
    • Journal of the Korean Vacuum Society
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    • v.5 no.1
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    • pp.1-5
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    • 1996
  • Noncrystalline films of diamond-like carbon (DLC) have been prepared by laser ablation technique at room temperature. A Q-switched Nd-YAG laser beam with wavelength of 1064 nm and pulse duration of 10 ns was focused onto a graphite target with power densities of about $10^9 W/\textrm{cm}^2$. The physical properties of the resulting films were analyzed with density, hardness, and resistivity measurements. The surface and bonding structure were investigated by atomic force microscopy (AFM), Raman spectroscopy, electron energy loss spectroscopy (EELS).

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Characteristics of micro-dimple formed on polyoxymethylene surface by Nd:YAG laser texturing technique (Nd:YAG 레이저를 이용한 polyoxymethylene 표면의 마이크로 딤플가공 및 특성에 관한 연구)

  • Cho, Min-Haeng;Lee, Jae-Bong;Lee, Seong-Hyuk;Kim, Joo-Han
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.193-197
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    • 2008
  • Array of micro-dimple on polyoxymethylene (POM) surface was fabricated using Q-switched Nd:YAG laser and its characteristics were studied in terms of heat affected zone (HAZ), dimple geometry, and the effect of specimen surface roughness. Process parameters such as lamp current, process time, and the stream of air in order to minimize HAZ and flow of molten polymer into cavity were extensively studied in this work. Dimple geometry was further investigated by 3-D optical microscopy to provide deep insight into morphological analysis near the dimples. This paper also presents the applicapability of micro-dimples in polymeric tribological system, such as a thrust bearing. Micro-dimples were expected to provide low coefficient of friction and enhanced lubricity at the sliding interface.

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WATER INDUCED MECHANICAL EFFECT ON THE DENTAL HARD TISSUE BY THE SHORT PULSED LASER

  • Kwon,Yong-Hoon;Kim, You-Young
    • Journal of Photoscience
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    • v.5 no.1
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    • pp.33-37
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    • 1998
  • One macroscopic effect in the free-running Er:YAG laser is an accumulation of microscopic effects. Understanding of the exogenous water induced mechanical effect on the dental hard tissue by the Qswitched Er:YAG laser has an important impact on the further understanding of the free-running Er:YAG laser ablation on the dental hard tissue. The Q-switched Er:YAG laser (1-$\mu$s-long pulse width) was used in the recoil pressure measurement with an aid of water-jet system and a pressure transducer. The amplitude of the recoil pressure depends on the tooth surface conditions (dry and wet) and the volume of the water upon it. Wet surfaces yielded higher recoil pressure than that of dry, surface, and as the volume of the exogenous water drop increased, the amplitude of the recoil pressure increased also.

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Experimental analysis of flow field for laser shock wave cleaning (레이저 충격파 클리닝에서 발생되는 유동장의 실험적 해석)

  • 임현규;장덕석;김동식
    • Laser Solutions
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    • v.7 no.1
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    • pp.29-36
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    • 2004
  • The dynamics of laser-induced plasma/shock wave and the interaction with a surface in the laser shock cleaning process are analyzed by optical diagnostics. Shock wave is generated by a Q-switched Nd:YAG laser in air or with N$_2$, Ar, and He injection into the focal spot. The shock speed is measured by monitoring the photoacoustic probe-beam deflection signal under different conditions. In addition, nanosecond time-resolved images of shock wave propagation and interaction with the substrate are obtained by the laser-flash shadowgraphy. The results reveal the effect of various operation parameters of the laser shock cleaning process on shock wave intensity, energy-conversion efficiency, and flow characteristics. Discussions are made on the cleaning mechanisms based on the experimental observations.

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