• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.534-537
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• 1995

An open loop vibrational control of underactuated mechanical system with amplitude and frequency modulations is investigated. The underactuated systems sonsidered in the paper are assumed to have free joints with no brake. The active joints are positioned first by a linearizing control, and then periodic oscillatory input are applied to them to move the remaining free joints to their desired states. A systematic way of obtaining averaged systems for the underactuated systems with oscillatory vibration is developed. A complete solution to the open loop control strateegy in terms of determining amplitudes and frequencies for general system is still under investigation. However, a specific control design for 2R manipulator which is obtained through the averaged system is demonstrated.

• 대한기계학회논문집
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• 제14권6호
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• pp.1464-1473
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• 1990

Optimal design parameters are estimated from the sensitivity function and performance index variation. Suspension design modification for performance improvement and basic materials for practical applications are presented. The linear quarter model of a vehicle suspension is analyzed in order to represent the utilities of sensitivity analysis, and sensitivity function is determined in the frequency domain. The change of frequency response function is predicted, which depends on the design parameter variation and the property is verified by computer simulation. As an investigation results of sensitivity function for the vibrational amplitude of sprung mass to road profile input, it is shown that the most sensitive parameters are the suspension damping and the suspension stiffness. In order to identify the effects of these two parameters to the performance of suspension system, the performance index variation according to the changes of parameters is considered and then optimal design parameters are determined. It is verified that the system response is improved noticeably in the both of frequency and time domain after the design modification with the optimal parameters.

• 한국소음진동공학회논문집
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• 제16권10호
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• pp.1044-1049
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• 2006

The vibration exciter with the accurate calibration requires a low distortion along a single axis over a wide range of frequency. The fabricated piezoelectric exciter was composed of a base, piezoelectric element(Venitron PZT 5A), electrode and seismic mass. Its performance characteristics is evaluated the Mach-Zehnder optical fiber interferometer. The phase of the optical wave passing through the optical fiber around the piezoelectric element was related the vibrational amplitude with a change of the applied sinusoidal voltage on the piezoelectric element. The dynamic characteristics of vibration exciter can be obtained by measuring the vibrational amplitude with a sinusoidal applied voltage on the piezoelectric element. The sensitivity of the fabricated piezoelectric exciter had a 0.4 nm/V which was uniform up to 20 kHz.

• 한국음향학회지
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• 제40권1호
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• pp.64-72
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• 2021

본 논문에서는 유체의 이동에 의한 배관의 진동을 저감시키기 위해 동조질량감쇠기(Tuned Mass Damper, TMD)의 최적 설계를 수행하였다. 배관 설비의 정확한 진원과 배관의 사양을 알지 못하는 상황에서 TMD 설계를 하기 위해 MATLAB을 이용하여 배관시스템 모델을 설계하고, 이를 바탕으로 최적 설계 방법을 개발하였다. 개발된 최적화 방법은 ANSYS Workbench에서 유한요소 모델을 이용해 최적 설계 방법을 검증했다. 그리고 실제 배관 시스템의 측정값을 바탕으로 진동수를 보정할 수 있도록 TMD를 설계 및 제작하고 실제 배관 시스템에 설치해 감쇠 진폭이 95% 수준으로 줄어든 것을 확인했다.

• Journal of the Optical Society of Korea
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• 제19권5호
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• pp.494-502
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• 2015

This paper introduces methods to measure vibration using a fringe pattern. These methods use variations of a fringe pattern in reflective monochromatic interferometry, without additional components. With the proposed methods we measured the vibrations of four waveform with amplitude 100 nm. When the vibrational amplitude is greater than a quarter wavelength of the light employed, however, the measured results are distorted due to ambiguity. Thus we propose advanced methods to solve this problem, and also measure the vibrations of two waveformswith an amplitude of $1{\mu}m$. To verify the performance of the proposed methods, we compare the results to those from an accelerometer. Multifrequency vibrations of 1, 5, 10, and 20 Hz are measured by both techniques, and the results compared in the frequency domain.

• 한국공작기계학회논문집
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• 제12권4호
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• pp.29-35
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• 2003

The rotating machineries always generate harmonic frequencies of their own rotating speed, and increment of vibration amplitude affects to the equipments which connected to the vibrational source and causes industrial calamities. The life cycle of equipments can be extended and damages to the human beings could be prevented by identifying the cause of malfunctions through prediction of the increment of vibration and records of vibrational history. In this study, therefore, diagnostic expert algorithm for the centrifugal pump is developed by integrating fuzzy inference method and signal processing techniques. And the validity of the developed diagnostic system is examined via various computer simulations.

• 소음진동
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• 제5권1호
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• pp.85-93
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• 1995

The vibration of the dehydration process in a washing machine is important problem that affects the performance of products. In this paper, the upper structure of a washing machine is modeled as rigid body suspension system and, by numerical analysis, the amplitude of a spin basket and the transfer moment at a base plate are calculated. To examine the vibrational characteristics according to design variable change, the friction coefficient in anubber, the radius of curvature, the stiffness coefficient, initial length and locations of support springs are considered in the analysis. Experimental results are compared with those of analysis.

• 한국음향학회지
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• 제1권1호
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• pp.65-69
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• 1982

It is studied on the apparatus for detecting the amplitude and the frequency of the vidrating object by utilizing the Ultrasonic Doppler Effect, without having any effect on the vibratioinal cases. The output detected varing the distance between the transducers and the vibrating object, when the angles of the incidence and the reflection wave are equalized. AM demodulatioin is adapted for the detection of vibration, and the output errors are theoretically consideed. The accurate detection of vibration can be obtained, when the distance between them is 5cm to 20cm, the magnitude of amplitude is 1mm to 5mm, and the vibrational frequency range is 20Hz to 1KHz.

• 한국소음진동공학회논문집
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• 제12권7호
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• pp.550-556
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• 2002

The vibrational system of this study is consisted of a cantilever pipe conveying fluid. the moving mass upon it and an attacked tip mass. The equation of motion is derived by using Lagrange equation. The influences of the velocity and the inertia force of the moving mass and the velocities of fluid flow in the pipe haute been studied on the dynamic behavior of a cantilever pipe by numerical method. As the velocity of the moving mass increases, the deflection of cantilever pipe conveying fluid is decreased. Increasing of the velocity of fluid flow make the amplitude of cantilever pipe conveying fluid decrease. The deflection of the cantilever pipe conveying fluid is increased by moving masses. After the moving mass passed upon the cantilever pipe, the amplitude of pipe is influenced due to the deflection of pipe tilth the effect of moving mass and gravity.

• Wind and Structures
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• 제5권1호
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• pp.61-80
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• 2002

Wind tunnel aeroelastic model tests of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building were conducted using a three-degree-of-freedom base hinged aeroelastic(BHA) model. Experimental investigation into the effects of coupled translational-torsional motion, cross-wind/torsional frequency ratio and eccentricity between centre of mass and centre of stiffness on the wind-induced response characteristics and wind excitation mechanisms was carried out. The wind tunnel test results highlight the significant effects of coupled translational-torsional motion, and eccentricity between centre of mass and centre of stiffness, on both the normalised along-wind and cross-wind acceleration responses for reduced wind velocities ranging from 4 to 20. Coupled translational-torsional motion and eccentricity between centre of mass and centre of stiffness also have significant impacts on the amplitude-dependent effect caused by the vortex resonant process, and the transfer of vibrational energy between the along-wind and cross-wind directions. These resulted in either an increase or decrease of each response component, in particular at reduced wind velocities close to a critical value of 10. In addition, the contribution of vibrational energy from the torsional motion to the cross-wind response of the building model can be greatly amplified by the effect of resonance between the vortex shedding frequency and the torsional natural frequency of the building model.