• 소음진동
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• 제10권6호
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• pp.1083-1093
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• 2000

이 논문은 지능구조물의 실시간 적응진동제어를 위해 유전자 알고리즘을 이용하여 Positive Position Feedback(PPF) 제어기를 조정하는 것과 관련이 있다. 유전자 알고리즘은 최적변수를 찾는데 있어 국소 최소점이 아닌 전체적인 최적점을 찾을 수 있는 능력이 있다. PPF 제어기는 다른 진동모드에 영향을 주지 않으면서 특정 진동모드의 감쇠를 증가시킬 수 있는 장점을 가지고 있는 반면에 효과적인 진동제어를 위해서는 제어하고 자하는 진동모드의 고유진동수를 정확히 알아야하는 단점이 있다. 본 연구에서는 유전자 알고리즘을 이용하여 실시간으로 PPF 제어기가 필요로 하는 변수값을 추적할 수 있는 알고리즘을 개발하여 그 타당성을 실험으로 증명하였다. 실험결과는 PPF 제어기의 실시간 조정이 성공적으로 이루어져 진동제어가 효과적으로 이루어졌음을 보여주고 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.306-311
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• 2002

Non-singular boundary element method (BEM) codes are developed in acoustics application. The BEM code is then used to calculate unknown boundary surface normal displacements and surface pressures from known exterior near Held pressures. And then the calculated surface normal displacements and surface pressures are again applied to the BEM in forward in order to calculate reconstructed field pressures. The initial exterior near field pressures are very well agreed with the later reconstructed field pressures. Only the same number of boundary surface nodes (1178) are used far the initial exterior pressures which are initially calculated by Finite Element Method (FEM) and BEM. Pseudo-inverse technique is used for the calculation of the unknown boundary surface normal displacements. The structural object is a tuning fork with 128.4 Hz resonant. The boundary element is a quadratic hexahedral element (eight nodes per element).

• 소음진동
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• 제9권4호
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• pp.761-768
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• 1999

This paper presents an NVH test of Automotive power steering system performed at a half-car Test-rig. The test was done for neutral and full turn(or relief) conditions in steering wheel at a fixed rpm first, then followed by the same conditions for the rpm run-up. The sound intensity measurement verified the results from the frequency and order analysis, especially about the identification of major noise sources and their dominant frequencies. The results from thie study can be utilized in the system noise tuning when a new steering component is installed. In particular, the noise and vibration reduction at the relief condition will be accomplished through the knowledge obtained from this study and from the on-going research on the hose tuning techniques usign silencers and tuning cable inserted in the pressure hose.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.897-900
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• 2007

Vehicles are exhausting various environmental pollutions such as exhaust gas, noise, and so on. This study investigates only noise problems by vehicles, especially the vehicle exhaust noise. It is known that the exhaust noise among those is over 20% of vehicle noise when the vehicle is suddenly accelerated or normally accelerated. In this study, we mainly investigate the exhaust noise of vehicle so that we intend to show the measures to decrease the illegal tuning mufflers and reduce the exhaust noise problems. In the conclusion, we suggest the new appropriate standard to control the tuning mufflers and reduce the exhaust noise induced by vehicles.

• 한국소음진동공학회논문집
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• 제18권12호
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• pp.1224-1228
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• 2008

Vehicles are exhausting various environmental pollutions such as exhaust gas, noise, and so on. This study investigates only noise problems by vehicles, especially the vehicle exhaust noise. It is known that the exhaust noise among vehicle noises is over 20% of those when the vehicle is suddenly accelerated or normally accelerated. In this study, we mainly investigate the exhaust noise of vehicle so that we intend to show the measures to decrease the illegal tuning mufflers and reduce the exhaust noise problems. In the conclusion, we suggest the new appropriate standard to control the tuning mufflers and reduce the exhaust noise induced by vehicles.

• 센서학회지
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• 제24권2호
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• pp.93-95
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• 2015

We present an optical detection method for the fundamental vibrational mode of a tuning fork crystal oscillator in air. A focused He/Ne laser beam is directed onto the edge of one vibrating tine of the tuning fork; its vibrating motion chops the incoming laser beam and modulates the intensity. The beam with modulated intensity is then detected and converted to an electrical signal by a high-speed photo-detector. This electrical signal is a sinusoid at the resonant frequency of the tuning fork vibration, which is 32.76 kHz. Our scheme is robust enough that the sinusoidal signal is detectable at up to $40^{\circ}$ of rotation of the tuning fork.

• 한국소음진동공학회논문집
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• 제19권1호
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• pp.64-75
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• 2009

최근 조선소에서 고출력 디젤엔진의 요구에 의해서 초대형 저속 2행정 디젤엔진이 개발되었으며, 연속최대출력이 $8{\sim}14$실린더를 갖는 10만 마력 이상의 엔진을 사용할 수 있게 되었다. 이러한 엔진들은 열효율, 운전에 대한 신뢰성, 강인성 및 기동성은 뛰어나지만 크랭크축을 포함한 추진축계에서 높은 비틀림진동을 유발한다. 따라서 이 연구에서는 엔진설계자의 입장에서 비틀림진동을 줄이기 위하여 튜닝 비틀림진동 댐퍼를 갖는 추진축계의 비틀림진동을 이론적으로 검토하였으며 실험모델인 12K98MC엔진과 12RT-flex엔진에서 튜닝댐퍼의 성능과 동적거동을 확인하고 있다.

• 한국정밀공학회지
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• 제10권1호
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• pp.134-141
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• 1993

Electro-Rheological(ER) fluids undergo a phase-change when subjected to an external electic field, and this phase-change typically manifests itself as a many-order-of-magnitude change in the rheological behavior. This phenomenon permits the global stiffness and energy- dissipation properties of the beam structures to be tuned in order to synthesize the desired vibration characteristics. This paper reports on a proof-of-concept experimental investigation focussed on evaluation the vibration properties of hollow cantilevered beams filled with an ER fluid. and consequently deriving an empirical model for predicting field-dependent vibration characteristics. A hydrous-based ER fluid consisting of corn starch and silicone oil is employed. The beams are considered to be uniform viscoelastic materials and modelled as a viscously-damped harmonic oscillator. Natural frequency, damping ratio and elastic modulus are evaluated with respect to the electric field and compared among three different beams: two types of different volume fraction of ER fluid and one type of different particle concentration of ER fluid by weight. Transient and forced vibration responses are examined in time domain to demonstrate the validity of the proposed empirical model and to evaluate the feasibility of using the ERfluid as an actuator in a closed-loop control system.

• 한국소음진동공학회논문집
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• 제21권10호
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• pp.940-950
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• 2011

This paper reports a filtered velocity feedback(FVF) controller, which is an alternative to direct velocity feedback(DVFB) controller. The instability problems at high frequencies due to non-collocated sensor/actuator configuration with the DVFB can be alleviated by the proposed FVF controller. The FVF controller is designed to filter out the unstable high frequency response. The dynamics of a clamped plate under forces and moments and the FVF controllers are formulated. The stability of the control system and performance are investigated with the open loop transfer function(OLTF). It is found that the FVF controller has a higher gain margin than the corresponding DVFB controller owing to the rapid roll-off behavior at high frequencies. Although the gain margin cannot be fully utilized because of the enhancement at the high frequencies, the vibration at the modes lower than the tuning frequency is well controlled. This performance of the FVF controller is shown to be improved from that of the DVFB controller. It is, however, noted that the stability around the tuning frequency is very sensitive so that the enhancement in vibration level should be followed. The reduction performance at low frequencies using the FVF controller should be compromised with the enhancement in the vibration at high frequencies while designing the controller.

• 한국소음진동공학회논문집
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• 제15권5호
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• pp.595-603
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• 2005

In this work, the multiple dynamic absorber( MDA ) is introduced to reduce several vibration modes of shadow mask simultaneously and its design method is developed from the theory of the simple dynamic absorber. When designing the dynamic absorber, there are three significant design parameters such as mass, damping ratio and tuning frequency. Therefore the sensitivity analysis for those parameters has been executed in order to find out the design criteria of multiple dynamic absorber using the finite element model of shadow mask. The multiple dynamic absorber(MDA) designed by the proposed method is tested theoretically and experimentally to estimate the efficiency of vibration reduction. From the results, it is verified that the method is feasible to apply the system having the multiple nitration modes and more efficient than the thin wire-type damper used commercially to reduce the vibration of shadow mask.