• 소음진동
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• 제8권1호
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• pp.75-80
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• 1998

It is a well known fact that the shaker used in the vibration test interacts with the test structure and thus influences the test results. A two degree of freedom model of shaker is suggested and the vibration parameters of this model is experimentally extracted. According to this experimental results, the vibration parameters of the shaker can vary with respect to the test structure as well as the stinger used in the connecting mechanism. It is also found that the vibration parameters of the shaker provided by the manufacturer can not be accurate and these parameter values should be revaluated based on the test environments.

• 한국소음진동공학회논문집
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• 제13권4호
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• pp.274-280
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• 2003

If a sinusoidal excitation force moves back and forth along a structure with a certain frequency, the structure will be excited with the difference frequency of these two frequencies. A low frequency vibration shaker has been developed using this force frequency shifting without actually moving a shaker The shaker consists of an ordinary eccentric mass shaker, a plate, constant springs, and time varying dampers. The dampers are turned on and off in a sequential manner to simulate a traveling slide of an excitation force. The operation of the shaker is simulated by solving the equations of motion of the shaker. Characteristics of the shaker have been found and they can be utilized to design efficient low frequency shakers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.182-186
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• 2002

If a sinusoidal excitation force moves back and forth along a structure with a certain frequency, the structure will be excited with the difference frequency of these two frequencies. A low frequency vibration shaker has been developed using this force frequency shifting without actually moving a shaker. The shaker consists of an ordinary eccentric mass shaker, a plate, constant springs, and time varying dampers. The dampers are turned on and off in a sequential manner to simulate a traveling slide of an excitation force. The operation of the shaker is simulated by solving the equations of motion of the shaker. Characteristics of the shaker have been found and they will be utilized to design efficient low frequency shakers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.324.2-324
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• 2002

If a sinusoidal excitation force moves back and forth along a structure with a certain frequency, the structure will be excited with the difference frequency of these two frequencies. A low frequency vibration shaker has been developed using this force frequency shifting without actually moving a shaker. The shaker consists of an ordinary eccentric mass shaker, a plate, constant springs, and time varying dampers. The dampers are fumed on and off in a sequential manner to simulate a traveling slide of an excitation force. (omitted)

• 반도체디스플레이기술학회지
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• 제14권1호
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• pp.31-37
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• 2015

This paper is on the design and manufacturing of vibration tester (shaker) for experiments about effects on the performance of semiconductor chips and Li-ion batteries by vibration. Shaker in the market are quite expensive, it is difficult for basic researchers to contact. In this study, in order to improve this, we designed and manufactured with an entry-level into mass production possible approaches in terms of performance required to a minimum. The shaker system is operated by Matlab and LabView. The target performances are 200Hz frequency and 5% error, and these were satisfied.

• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.165-175
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• 2018

Jet Propulsion Laboratory has traditionally performed system level vibration testing of flight spacecraft. There have been many discussions in the aerospace community for more than a decade about spacecraft vibration testing benefits or lack thereof. The benefits and potential issues of fully assembled flight spacecraft vibration testing are discussed herein. The following specific topics are discussed: spacecraft screening test to uncover workmanship problems for launch dynamics environments, force- and moment-limited vibration testing, potential issues with structural frequency identification using base shake test data, and failures related to vibration shaker testing and ways to prevent them.

• Advances in aircraft and spacecraft science
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• 제5권2호
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• pp.251-258
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• 2018

This work illustrates the progress of a TAS activity at exploring the challenges and the benefits of the Virtual Shaker Testing (VST) approach. The definition and the validation of new computational methodologies with respect to the state of the art were encouraged throughout this activity. The shaker Finite Element (FE) model in lateral configuration was built for the purpose and it was merged with the SpaceCraft (S/C) FE model, together with the S/C-Shaker adapter. FE matrices were reduced through the Craig-Bampton method. The VST transient analysis was performed in MATLAB(R) numerical computing environment. The closed-loop vibration control is accounted for and the solution is obtained through the fourth-order Runge Kutta method. The use of pre-existing built-in functions was limited by authors with the aim of tracing the impact of all the problems' parameters in the solution. Assumptions and limitations of the proposed methodology are detailed throughout this paper. Some preliminary results pertaining to the current progress of the activity are thus illustrated before the conclusions.

• 한국지진공학회논문집
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• 제11권2호
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• pp.27-38
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• 2007

노스리지 지진에 의해 손상을 받은4층 철근콘크리트조 골조건물을 대상으로 선형가진기 및 대용량의 편심가진기를 이용한 강제진동실험과 상시미진동 측정을 실시하였다. 미진동 가속도데이터 및 선형가진기에 의한 백색잡음 실험시의 가속도데이터로부터 구조물식별을 수행하여 7차모드까지의 고유진동수 및 모드감쇠비를 얻었다. 두대의 대용량 편심가진기를 사용하여 얻은 큰 진폭의 조화 진동하에서는 가속도데이터를 사용하여 각 방향 1차모드를 식별하였으며 변위계와 변형게이지를 이용하여 층간변위각, 기둥과 슬래브와 같은 구조부재의 곡률분포를 측정하였다. 각 경우 고유진동수는 진동의 크기가 클수록 낮아졌다. 즉, 편심가진기가력시 고유진동수는 상시미진동시에 비해 $70{\sim}75%$, 선형가진시가력시에 비해 $92{\sim}93%$ 정도로 낮게 나타났다. 이러한 진동수의 감소폭은 지진에 의해 큰 손상을 받았던 건물의 남북방향에서 크게 나타났다.

• Advances in aircraft and spacecraft science
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• 제7권1호
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• pp.79-90
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• 2020

The dynamic coupling between shaker and test-article has been investigated by recent research through the so called Virtual Shaker Testing (VST) approach. Basically a VST model includes the mathematical models of the test-item, of the shaker body, of the seismic mass and the facility vibration control algorithm. The subsequent coupled dynamic simulation even if more complex than the classical hard-mounted sine test-prediction, is a closer representation of the reality and is expected to be more accurate. One of the most remarkable benefits of VST is the accurate quantification of the frequency down-shift (with respect to the hard-mounted value), typically affecting the first lateral resonance of heavy test-items, like medium or large size Spacecraft (S/Cs), once mounted on the shaker. In this work, starting from previous successful VST experiences, the parameters having impact on the frequency shift are identified and discussed one by one. A simplified analytical system is thus defined to propose an efficient and effective way of calculating the lower bound frequency shift through a simple equation. Such equation can be useful to correct the S/C lateral natural frequency measured during the test, in order to remove the contribution attributable to the shaker in use. The so-corrected frequency value becomes relevant when verifying the compliance of the S/C w.r.t. the frequency requirement from the Launcher Authority. Moreover, it allows to perform a consistent post-test correlation of the first lateral natural frequency of S/C FE model.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1732-1738
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• 2003

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the under-test, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.