• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.390-394
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• 2013

고정밀 광학계를 탑재한 관측 위성은 매우 높은 지향 안정성을 요구하지만 인공위성의 자세 제어를 위해 사용하는 반작용 휠, 극저온 냉각을 위한 cooler 등 다양한 진동원에 의해 미소 진동이 발생할 수 있다. 고정밀 탑재체를 외부 진동으로부터 보호하기 위한 가장 일반적인 방법은 진동이 전달되는 경로에 진동 절연장치를 도입하는 것이다. 본 논문에서는 미소진동 절연을 위한 1 축 능동 진동 절연장치의 개발 및 진동 절연 성능 시험을 기술하였다. 개발한 절연장치의 고유진동수를 조절하기 위해 원하는 강성을 갖는 membrane 구조를 설계하였으며 능동 제어를 위해 전자석을 사용하였다. 절연장치의 성능 시험 결과를 통해 능동 제어 시 고주파수 대역에서 절연성능의 저하 없이 공진의 크기를 줄일 수 있는 것과 개발된 진동 절연 장치가 미소 진동을 효과적으로 절연할 수 있는 것을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.432-441
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• 2008

In this study, the control performance of a Tuned Liquid Mass Damper(TLMD) manufactured to reduce the orthogonal bi-directional responses of building structures was experimentally evaluated. the TLMD using only one control device reduce bi-directional responses of building structures by making the TLMD behave as TMD and TLCD to the strong and weak axial direction of building structures. first, the control performance was evaluated by forcing sinusoidal waves to a test model that the TLMD is installed on the scale-downed building structure. Second, the real-time hybrid shaking table test was performed to evaluate the performance of the vibration control system made up of numerical part as a scale-downed building structural model and a physical experimental part as a TLMD. the superiority of bi-directional vibration control performance of the manufactured TLMD was verified by comparing the uncontrolled and controlled results of these tests.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.381-385
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• 2014

This paper investigates the magneto-rheological(MR) mount for the marine diesel-generator(D/G) sets. Sometimes, significant vibrations over the allowable limit are observed on the D/G sets due to their huge excitation forces. Because the severe vibration can lead to structural damages to the D/G sets, it should be reduced below the limit. Although passive mounts with rubber isolators are usually used, the vibration reduction performance is not always sufficient. In addition, expecting that the vibration levels required by customers will get more severe, vibration reduction devices need to be developed. To the aim, the flow mode type of MR mount has been designed. Especially, the annular-radial configuration was adopted to enhance the damping force within the restricted space. The geometry of the mount has been optimized to obtain the required damping force and the magnetic field analysis has been carried out using ANSYS APDL. To verify the performance of the developed MR mount, an excitation test was conducted. In addition, they were applied to a medium-speed diesel generator and it was verified that about 40% of vibration reduction was yielded.

• 한국소음진동공학회논문집
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• 제23권3호
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• pp.218-225
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• 2013

Vertically-launched missiles are supported as erected vertically in the vertical launching system of warship, and they should be mounted in the same way when vibration-tested. However, mounting missiles vertically makes a fixture, which is a supporting structure, bulky and heavy so requiring a high-performance exciter. Mounting missiles as laid down horizontally in a vibration test is economical regarding fixture manufacturing and exciter performance, but it makes test results incorrect because the different mounting direction has effects on the test results. A bending moment due to missiles' weight happens to missiles, and resilient mounts, which support missiles in the vertical launch system, deflect differently from the real situation because of the static deflection of these mounts due to missiles' weight. If the resilient mounts supporting missiles have nonlinear force-deflection characteristics, vibration test results become more different from the true results. This paper proposes to support missiles with an additional resilient mount such as a bunge code in order to solve those problems coming from mounting vertically-launched missiles as laid down horizontally in vibration tests. The proposed approach enables to obtain the same test results as in their actual mounting condition even though vertically-launched missiles are mounted in a different direction.

• 한국군사과학기술학회지
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• 제8권4호
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• pp.130-135
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• 2005

This paper presents application possibility of Lightweight Piezoceramic Composite Actuator(LIPCA) to suppress vibration of dynamic structures as an actuator. LIPCA is composed of a piezoelectric layer, a carbon/epoxy layer and glass/epoxy layers. When compared to the bare piezoelectric ceramic(PZT), LIPCA has advantages such as high performance, durability and reliability. In this study, performances of LIPCA have been estimated in an active vibration control system. Experiments were performed on an aluminum beam with cantilever configuration. In this test, strain gages and single LIPCA are attached on the aluminum beam with epoxy resin. Digital ON-OFF control algorithm is applied into the system to exhibit performance of LIPCA as actuator in active vibration control system. First, we performed static actuation test of bare PZT and LIPCA in order to show the superiority of LIPCA. Secondly, we carried out beam vibration control test using LIPCA. The results showed LIPCA could suppress free vibration of the aluminum beam, which means that LIPCA can be applied as an actuator to control vibration of dynamic structures.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.893-899
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• 2014

X-band antenna has been widely used to effectively transmit the high resolution image data from the observation satellite to the ground station. To achieve above mission, X-band antenna is mainly composed of the 2-axis gimbal system using stepping motors and gears. However, the micro-vibration induced by the stepping motor actuation and the imperfect gear teeth alignment during this on-orbit operation is the main source of image quality degradation. In this paper, X-band antenna combined with a blade gear for micro-vibration isolation was suggested and investigated. The structural safety of the blade gear with low rotational stiffness was confirmed by structure analysis based on the derived torque budget. The isolation performance of the X-band antenna with the blade gear was verified through micro-vibration measurement test using the dedicated micro-vibration measurement device proposed in this study.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1128-1133
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• 2003

A gas driven heat pump (GHP) core design comprises internal combustion engine, compressors incorporated to a cooling/heating system, rubber mountings and belt transmissions. Main excitation farces are generated by an engine, compressors themselves and belt fluctuation. It leads to high vibration level of the mount that can cause damage of GHP elements. Therefore an appropriate design of the mounting system is crucial in terms of reliability and vibration reduction. In this paper oscillation of the engine mount is explored both experimentally and analytically. Experimental analysis of natural frequencies and operational frequency response of the GHP engine mounting system enables to create simplified model for numerical and analytical investigations. It is worked out criteria f3r vibration abatement of the isolated structure. Influence of bracket stiffness between engine and compressors, suspension locations and damper performance is investigated. Ways to reduce excitation forces and improve dynamic performance of the engine-compressor mounting system are considered from these analyses. Implementation of the proposed approach permits to choose appropriate rubber mountings and their location as well as joining elements design A phase matching technique can be employed to control forces from main exciters. It enables to changing vibration response of the structure by control of natural modes contribution. Proposed changes lead to significant vibration reduction and can be easily utilized in engineering practice.

• Structural Engineering and Mechanics
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• 제29권5호
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• pp.489-504
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• 2008

In piezoelectric flexible structures, the contribution of vibration modes to the dynamic response of system may change with the location of piezoelectric actuator patches, which means that the ability of actuators to control vibration modes should be taken into account in the development of modal reduction model. The spatial $H_2$ norm of modes, which serves as a measure of the intensity of modes to system dynamical response, is used to pick up the modes included in the reduction model. Based on the reduction model, the paper develops the state-space representation for uncertain flexible tructures with piezoelectric material as non-collocated actuators/sensors in the modal space, taking into account uncertainties due to modal parameters variation and unmodeled residual modes. In order to suppress the vibration of the structure, a dynamic output feedback control law is designed by imultaneously considering the conflicting performance specifications, such as robust stability, transient response requirement, disturbance rejection, actuator saturation constraints. Based on linear matrix inequality, the vibration control design is converted into a linear convex optimization problem. The simulation results show how the influence of vibration modes on the dynamical response of structure varies with the location of piezoelectric actuators, why the uncertainties should be considered in the reductiom model to avoid exciting high-frequency modes in the non-collcated vibration control, and the possiblity that the conflicting performance specifications are dealt with simultaneously.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.205-208
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• 2005

Fabrication of large scaled mirror for the telescope application is the most challenging technology in recent year. Sophisticate technologies and know-how in fabrication and measurement are required to overcome the technological obstacles. KRISS(Korea Research Institute for Standards and Science) is now developing a large scaled mirror fabrication facility and KARI(Korea Aerospace Research Institute) is supporting the development. High precision interferometric test is required during the grinding and polishing of mirror to identify the surface profile precisely. The required fabrication accuracy of the mirror surface profile is $\lambda$/50 ms($\sim$10 nm for visible wave length). Thus the measurement accuracy should be far less than 10 m. To get this requirement, it is necessary to provide vibration free environment for the interferometer system and mirror under test. Thus the vibration responses on the mirror supporting table due to external vibration should be minimized by using a special isolation system. And the responses on the top of the tower, which hold the interferometer during test, should be minimized simultaneously. In this paper, we propose the concept design of vibration suppression system for the KRISS mirror fabrication facility.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.1141-1145
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• 2001

An orifices fluid damper having the capacity of about 2 tons was designed and fabricated, and series of tests were performed to grasp the fundamental performance characteristics of it. Several important findings were observed and introduced in this paper. This fabricated orifices fluid damper will be applied to the structure under seismic load for the confirmation of its validity on structural vibration absorbtion as an extended study.