• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.681-682
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• 2009

• Coupled systems mechanics
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• v.2 no.4
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• pp.303-327
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• 2013

The coupled free vibration of flexible structures and on-board liquid in zero gravity space was analyzed, considering the spacecraft main body as a rigid mass, the flexible appendages as two elastic beams, and the on-board liquid as a "spring-mass" system. Using the Lagrangians of a rigid mass (spacecraft main body), "spring-mass" (liquid), and two beams (flexible appendages), as well as assuming symmetric motion of the system, we obtained the frequency equations of the coupled system by applying Rayleigh-Ritz method. Solving these frequency equations, which are governed by three system parameters, as an eigenvalue problem, we obtained the coupled natural frequencies and vibration modes. We define the parameter for evaluating the magnitudes of coupled motions of the added mass (liquid) and beam (appendages). It was found that when varying one system parameter, the frequency curves veer, vibration modes exchange, and the significant coupling occurs not in the region closest to the two frequency curves but in the two regions separate from that region.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.308-313
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• 2012

Robust tuning rules of the motion profile are proposed to minimize the residual vibration. For asymmetric S-curve profile, tuning rules are analytically formulated using Laplace-domain approach. When the system modeling is known exactly, by placing a single zero of the motion profile on the pole of the system, the residual vibration can be perfectly eliminated under undamped system. However, if there are some amounts of the modeling errors, the residual vibration significantly increases. To track this issue, the robust tuning rules against modeling error are discussed. One of the proposed robust tuning rules is placing the multiple zeros of the motion profile on the pole of the system, and the other is placing the zeros of the motion profile around the pole of the system. Thanks to the proposed robust tuning rules, motion profile becomes more robust to modeling errors while minimizing the residual vibration. By simulation, the effectiveness of the proposed robust tuning rules is verified.

• Korean Journal of Agricultural Science
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• v.17 no.2
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• pp.115-129
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• 1990

This study was carried out to develop a microcomputer-based data acquisition system and software for analysis of engine vibration. Due to this development of system and software, studies on the vibration of engine was able to conduct efficiently. From the display of CRT, the outputs of test was compared and analysed on a zero-base motoring. The results obtained are summarized as follows : 1. Data acquisition system in microcomputer were designed and programmed and operated accurately. 2. The result of test was easily compared in monitoring of zero-base at color monitor. 3. This system and program developed was able to control the measuring intervals, no. of channels, and no. of data as wated. 4. The type of vibration of engine was type of bi-mode from the FFT and statistical analysis. 5. The maxima of engine vibration were 9.11 G at X-axis. 11.27 G at Y-axis, and 4.9 G at Z axis for full load of net output 6. The maxima of engine vibration unloaded were 4.28 G, 5.59 G, 2.68 G at 2200 rpm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1918-1924
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• 2000

Dynamic characteristics of a vertically coupled structure used for micro gyroscopes, is studied. The coupled motion between the reference and sensing vibrations causes the zero-point output which means non-zero sensing vibration without angular velocity. This structural coupling deteriorates sensing performance and dynamic stability. We theoretically analyze dynamic characteristics associated the coupling phenomenon. Effects of reference frequency and coupling factor on the rotational direction and amplitude of elliptic oscillation are studied. A method to predict the existence of curve veering or crossing in frequency trajectories is introduced for the application to the design of micro gyroscopes with a vertically decoupled structure.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.112-119
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• 2001

A variety of input shaper has been proposed to reduce the residual vibration of flexible structures. Multi-hump input shaper is known to be robust for parameter variations. However, existing approach should solve the more complicated nonlinear simultaneous equations to improve the robustness of the input shaper with the additional constraints. In this paper, by proposing a graphical approach which uses convolution of shaper, the multi-hump convolution input shaper could be designed even if the constraints are added for further robustness. With a mass-damper-spring model, the better performance is obtained using the proposed new multi-hump convolution input shaper.

• Journal of Biosystems Engineering
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• v.18 no.4
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• pp.317-327
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• 1993

This study was carried out to develop a microcomputer-based data acquisition system and software for analysis of engine vibration. Due to this development of system and software, studies on the vibration of engine was able to conduct efficiently. From the display of color monitor, the outputs of test were compared and analysed on zero-base monitoring. The results obtained are summarized as follows : 1. Data acquisition system in microcomputer was designed and programmed and operated accurately. 2. The results of test were easily compared in monitoring of zero-base at color monitor. 3. The system and program developed was able to control the measuring intervals, number of channels, and number of data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.385-392
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• 2001

Time-dependent frequency and energy of free vibration of the Spagetti problem, that is the axially moving continuum with time-varying length, are investigated. Exact expressions for the natural frequency and time-varying vibration energy are derived by dealing with traveling waves. When the string length is increased, the vibration period increases, but the free vibration energy varies as a function of both translating velocity and boundary velocity of the continuum. However, when the string undergoes retraction, the vibration energy increases with time, String tension together with non-zero instantaneous velocity at the moving boundary results in energy variation.

• Journal of KSNVE
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• v.9 no.5
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• pp.906-913
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• 1999

Time-dependent period and energy of free vibration of a string, whose length varies with time at a constant rate, are investigated by a traveling wave method. When the string length is increased, the vibration period increase, but the free vibration energy decrease with time. However, when the string undergoes retraction, the vibration energy increases with time. String tension together with non-zero instantaneous velocity at the moving boundary results in energy variation. Analytical solutions by the traveling wave method are compared with previous results using the perturbation method and Kotera's approach.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.354-361
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• 1997

본 연구에서는 우선적으로 수도권 대량운송 수단인 지하철 전동차의 진동을 측정하고 인체에 미치는 영향을 평가하였으며 전동차의 진동특성이 인체 각 부위에 전달되는 형태를 분석.평가함으로써 승객과 승무원의 승차감 및 작업환경 향상은 물론 차후 개발되는 고속전철 및 비접지 차량(zero-ground pressure vehicle) 등의 개발에 필요한 기초자료를 제공하고자 한다.