• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.825-828
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• 2005

Experimental and numerical study was done to confirm the effect of the flexible tube in pipeline on transient flow oscillation. Experiment was made for a pipeline with and without deformable flexible tube using a single pumping system of main stainless pipe. The wave speeds of main pipe and flexible tube were calculated from the pipe material properties, structures, and boundary conditions. Time dependent pressure fluctuations were calculated for the pipeline using the simple and the Kelvin-Voigt viscoelastic models for the deformation of main pipe and flexible tube. Pressure calculated by the Kelvin-Voigt viscoelastic model showed better agreement with measured one than pressure by the simple model. Experimental and numerical results show that the maximum pressure as well as amplitude of pressure oscillation was decreased by inserting short flexible tube in pipeline. Hence, inserted short flexible tube to pipeline was found to be effective for the suppression of strong pressure oscillation. Moreover, the wave speed in pipe was discussed based on numerical and experimental results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.197-201
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• 2010

정확한 산화제 유량조절은 하이브리드 로켓의 추력제어에 매우 중요하다. 산화제 유량제어를 위해 스텝모터와 니들밸브를 결합하여 장치하고 Labview 프로그램으로 제어하는 산화제 유량제어 장치를 설계하였다. 하이브리드 로켓 연소실험에 사용한 산화제는 기체산소를 사용하였고, 추진제로는 PolyCarbonate, PolyEthylene PMMA를 사용하였다. 본 연구에서는 초기 추력제어 실험에서 발생한 추력 섭동(Oscillation)을 감쇠시키기 위한 연구로 추력제어 실험에서 공급되는 산화제 배관 유속의 변화를 통해 발생되는 추력 섭동의 원인을 분석하였으며, 추진제 종류에 따라 달라지는 안정적인 제어 조건을 찾기 위한 연구를 수행하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.265-270
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• 2001

This study presents a feedback control methodology for suppression of the vortex shedding from a circular cylinder in a uniform flow. A rotational oscillation is applied as a controlled forcing and the lift coefficient ($C_L$) is used as a feedback signal. A feedback control concept is made based on the phase relation between the rotation velocity and $C_L$ at 'lock-on', The phase between the forcing and the vortex formation is changed $180^{\circ}$ from the phase of enhancing the lock-on state. This concept is examined by solving the Van del Pol equation. The results are satisfactory.

• 대한기계학회논문집
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• 제18권4호
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• pp.1081-1086
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• 1994

The phenomena called "combustion instabilities" in a solid-propellant rocket motor may be viewed as sustaining or amplifying pressure waves. Energy is supplied by combustion processes near the surface of the burning propellant. T-burner method is used to determine the response function of the propellant to the pressure wave. But initial tests were failed because of the Helmholtz resonation inside the T-burner. Acoustic analysis of the original T-burner is carried out and suppression techniques for the Helmholtz oscillation are introduced.ntroduced.

• 대한기계학회논문집A
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• 제33권5호
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• pp.463-468
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• 2009

Torsional oscillations of the drivetrain in electric vehicles are generated under rapid driving conditions. These lead to an uncomfortable jerking of the vehicle and an increased stress of the mechanical components. To suppress torsional oscillations, the low pass and notch filters between the torque command from the acceleration pedal and electric motor input torque are suggested. The filter parameters are optimized based on Taguchi method with $L_{18}(3^5)$ orthogonal array. The signal to noise (S/N) ratio mainly depends on slew rate of motor input torque, damping ratio and natural frequency of notch filter. With the proposed suppression control scheme, the S/N ratio is shown to be increased by 4.7dB and the torque overshoot of the drive shaft is reduced to 30%.

• International Journal of Control, Automation, and Systems
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• 제5권3호
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• pp.223-233
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• 2007

Crane payloads frequently swing with large amplitude motion that degrades safety and throughput. Open-loop methods have addressed this problem, but are not effective for disturbances. Closed-loop methods have also been used, but generally require the speed of the driving motors to be precisely controlled. This paper develops a feedback control method for controlling motors to cancel the measured payload oscillations by intelligently timing the ensuing on and off motor commands. The effectiveness of the oscillation suppression scheme is experimentally verified on an industrial bridge crane.

• 한국광학회지
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• 제13권1호
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• pp.58-64
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• 2002

마하젠더형 광세기 변조기를 이용하여 l0 GHz 고조모드잠금된 분산보상 어븀첨가 광섬유 레이저의 출력 안정화 되먹임 제어를 하고 출력의 안정도를 측정하였다. 레이저의 출력 불안정성이 발생하였을 때 나타나는 완화진동 주파수 성분을 억압하도록 공진기 길이를 조정하여 16시간 이상 출력 안정화를 시켰다. 이때, 안정화가 진행되는 동안 rms 위상잡음과 rms진폭잡음은 각각 260 fsec-524 fsec와 4-11.5%의 사이에 분포하였고, BER은 $10^{-13}$ 으로 측정되었다.

• Journal of Power Electronics
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• 제15권5호
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• pp.1409-1420
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• 2015

In this paper, an algorithm using two bi-quad filters to suppress the wide-band resonance for PMSM servo systems is proposed. This algorithm is based on the double bi-quad filters structure, so it is named, "double bi-quad filter." The conventional single bi-quad filter method cannot suppress unexpected mechanical terms, which may lead to oscillations on the load side. A double bi-quad filter structure, which can cancel the effects of compliant coupling and suppress wide-band resonance, is realized by inserting a virtual filter after the motor speed output. In practical implementation, the proposed control structure is composed of two bi-quad filters on both the forward and feedback paths of the speed control loop. Both of them collectively complete the wide-band resonance suppression, and the filter on the feedback path can solve the oscillation on the load side. Meanwhile, with this approach, in certain cases, the servo system can be more robust than with the single bi-quad filter method. A step by step design procedure is provided for the proposed algorithm. Finally, its advantages are verified by theoretical analysis and experimental results.

• 한국생산제조학회지
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• 제21권6호
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• pp.878-884
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• 2012

In this paper, we consider the sway suppression control problem for container cranes with the frictions between the trolley and the rail. If the friction effects in the system can be modelled, there is an improved potential to design controllers that can cancel the effects. The proposed control improves the trolley positioning and sway suppressing against various frictions. The proposed synthesis combines a variable structure control and the adaptive control to cope with various frictions including the unknown constants. First, the variable structure control with the simple switching action is designed, which is based on a class of feedback lineariztion methods for the fast stabilization of the under-actuated sway dynamics of container. Second, the adaptive control with a parameter estimation is designed, which is based on Lyapunov stability methods for suppressing the oscillation of the trolley travelling, especially due to Coulomb friction in the vicinity of the target position. The asymptotic stability of the overall closed-loop system is assured irrespective of variations of rope length. Simulation are shown under initial sway, external wind disturbances, and various frictions.

• 한국전자통신학회논문지
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• 제8권9호
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• pp.1277-1283
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• 2013

본 논문에서는 마이크로스트립라인 종단형 CSRR구조를 이용하여 X-band 레이다에 사용하는 새로운 전압 제어 발진기를 제안하였다. 마이크로스트립 종단형 CSRR을 발진기와 버퍼 사이에 삽입되는 필터로 사용하여 고주파억압특성을 개선하였다. 측정 결과 제어전압을 0~10V로 가변 하였을 때 9.28~9.39GHz가 발진 하였으며 발진주파수 9.35GHz에서 16.6dBm의 높은 출력을 얻을 수 있었다. 또한 일반적인 발진기 보다 고주파억압 특성이 10.4dB 개선되었다.