• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1396-1403
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• 2006

This study shows that the system performance of a positioning system composed of a piezoelectric actuator-driven flexure guide depends largely on the preload applied on the flexure guide and the driving input amplitude. We used a flexure guided system that had an original resonant frequency of 54Hz. Our experiment showed that we could increase the driving bandwidth above the original resonant frequency, for a case involving a large preload and a small input amplitude. Results show that there is a specific 'separation frequency' where the response of the moving mass of the flexure system decouples from the response oi the piezoelectric actuator, and this specific separation frequency can be selected by a proper choice of the preload and the input amplitude. To find the separation frequency, sine sweep tests were performed. To confirm the increased system bandwidth frequency, open-loop sine tracking experiments were performed. Test results show that the system responds very well up to 130 Hz frequency higher than the original natural frequency (54Hz).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.346-354
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• 2006

This study shows that the system performance of a positioning system composed of a piezoelectric actuator-driven flexure guide depends largely on the preload applied on the flexure guide and the driving input amplitude. We used a flexure guided system that had an original resonant frequency of 54 Hz. Our experiment showed that we could increase the driving bandwidth above the original resonant frequency, for a case involving a large preload and a small input amplitude. Results show that there is a specific 'separation frequency' where the response of the moving mass of the flexure system decouples from the response of the piezoelectric actuator, and this specific separation frequency can be selected by a proper choice of the preload and the input amplitude. To find the separation frequency, sine sweep tests were performed. To confirm the increased system bandwidth frequency, open-loop sine tracking experiments were performed. Test results show that the system responds very well up to 130 Hz frequency higher than the original natural frequency (54 Hz).

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.167.2-167.2
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• 2012

경희대학교와 UC Berkeley, Imperial College London에서 공동으로 진행하는 TRIO-CINEMA Mission(TRiplet Ionosphere Observatory-Cubesat for Ion, Neutral, Electron and MAgnetic fields)은 총 3기의 초소형 위성으로 구성되어 있다. 3기의 위성은 고도 650~800km 상공의 태양동주기 궤도운동을 예상하고 있으며, 지구 근접공간의 입자 검출과 자기장 측정의 과학 임무를 맡게 된다. TRIO-CINEMA 비행 모델(Flight Model)의 환경시험은 진동시험과 열진공시험으로 진행되었다. 진동시험은 X, Y, Z 세 축에 대해 Sine 과 Random 모드로 진행되었다. TRIO-CINEMA가 탑재 될 러시아의 드네프르 로켓의 요구사항은 각 축에서 20Hz 이상의 고유진동수, Sine의 경우 최대 0.8G와 4oct/min Sweep Rate, Random의 경우 5.2Grms 와 35초의 지속시간에서의 안정성을 만족하는 것이다. 시험 결과 TRIO-CINEMA가 요구사항을 모두 만족시키는 것을 확인하였다. 또한, 열 주기 시험(Thermal Cycling Test)을 진행하여 우주공간에서 위성 시스템이 정상 동작하는지에 대한 신뢰성을 검증하였다. 열주기 시험은 미국 MIL표준 값을 참고하여 $10^{-6}Torr$에서 $-20{\sim}30^{\circ}C$의 온도를 주었으며, 시험을 진행하는 동안과 시험 후에 위성이 정상작동 함을 확인하였다. 이에 본 연구의 시험 방법과 그 결과를 기술하였다.

• The Journal of Engineering Geology
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• v.33 no.2
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• pp.293-305
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• 2023

Three ground models are analyzed using a 1g shaking table and laminar shear box (LSB) to investigate the impact of the ground structure on seismic wave amplification during earthquakes. Multi-layer horizontal, embankment, and basin ground models are selected for this investigation, with each model being divided into dense and loose ground layers, Accelerometers are installed during the construction of each ground model to capture any seismic wave amplification owing th the propagation of an artificial seismic wave, sine wave sweep, and 10-Hz sine wave through a given ground model. The amplification of the tested seismic waves is analyzed using the observed peak ground acceleration and spectrum acceleration. The observed acceleration amplification in the multi-layer horizontal ground model is significantly higher the seismic waves that propagated across the dense ground-loose ground boundary compared with those that only propagated through the dense ground. Furthermore, the observed acceleration amplification gradually increases in the central part of the multi-layer embankment and basin models for the seismic waves that propagated across the dense ground-loose ground boundary.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.19-22
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• 2001

This paper proposes a double cantilever sandwich-beam method for evaluating the frequency dependence of material dynamic characteristics. The flexural vibration of a double cantilever sandwich-beam specimen with a partially inserted rubber layer was studied using a finite element simulation in combination with the sine-sweep test. Quadratic relationships of dynamic elastic modulus and material loss factor of rubbers with frequency were quantitatively suggested employing the least square error method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.225-233
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• 2002

The flexural vibration characteristics of a sandwich beam system with a partially inserted viscoelastic layer have been quantitatively studied using a finite element analysis in combination with a sine-sweep test. Antisymmetric mode shapes of the flexural vibration were visualized by the holographic interferometry and agreed with those calculated by the finite element simulation. Effects of the beam thickness as well as the length and thickness of partial viscoelastic layers on the system loss factor(η$\_$s/) and resonant frequency($\omega$$\_$r/) were significantly large fur the symmetric and antisymmetric modes of the beam system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.957-961
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• 2005

A satellite component must withstand vibration caused when launch vehicle acoustics and engine rumble transfer to it through its structural mount. Components shall be subjected to environmental tests after manufacturing process thus the environmental test conditions are needed for component level test including vibration and shock. This paper deals with derivation of component-level environmental test specifications, especially for solar panels of STSAT-2(Science & Technology SATellite-2). Sine sweep random vibration, and shock test conditions were generated for solar panels by assuming the satellite as single-degree-of-freedom system with a base excitation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.718-721
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• 2007

The ionic-polymer-metal-composite actuators have the best merit for bio-mimetic locomotion because of their large bending performance. Especially, they have the advantage for mimicking a fish-like motion because IPMCs are useful to be actuated in water. So we have developed IPMC actuators with multiple electrodes for realization of biomimetic motion. This actuator is fabricated by combining electroless plating and electroplating techniques capable of patterning precisely and controlling a thickness of Pt electrode layer. The FRF analysis was conducted by a mechanical shaker and direct electrical excitation which is based on sweep sine wave function. From this result, the proper young‘s modulus of Platinum was investigated and applied on expecting the vibration characteristics of patterned IPMC actuator. The calculated maximum displacement of the patterned IPMC was 2.32mm under an applied 4mN/mm. The natural frequency was increased however displacement was decreased in according to increase a thickness of Pt.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.676-681
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• 2002

System Identification is carried out for a full scale five-story builing to design a vibration controller. Dynamic characteristics such as natural frequencies, damping ratios, and modes are obtained from the input/output information by both sine-sweep method and white noise method. The active mass driver installed on the five floor is applied as external loading to move the building and each floor acceleration is measured and processed for the system identification. The identified building will be experimentally investigated again with viscoelastic dampers installed at inter-stories to obtain the response behavior. Corresponding result will be presented soon.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.10
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• pp.808-815
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• 2002

The nonlinear characteristics for hinge of a deployable missile control fin are investigated experimentally. The nonlinearity is caused by a worn or loose hinge and manufacturing tolerance and cannot be eliminated completely. The structural nonlinearity has an effect on the static and dynamic characteristics of the control fin. Therefore, it is necessary to establish the accurate nonlinear model for the hinge of the control fin. In the present study the existence of nonlinearities in the hinge is confirmed from the frequency response experiments such as tip random excitation and base sine sweep. Using the system identification method. especially, ″Force-state Mapping Technique″, the types of nonlinearities are identified and the nonlinear hinge model of the control fin is established.