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구조물의 진동장 예측 최적센서배치를 위한 유전자 알고리듬 적합함수의 선정
정병규(Byung-Kyoo Jung),배경원(Kyeong-Won Bae),정의봉(Weui-Bong Jeong) 한국소음진동공학회 2015 한국소음진동공학회 논문집 Vol.25 No.10
It is often necessary to predict the vibration patterns of the structures from the signals of finite number of vibration sensors. This study presents the optimal placement of vibration sensors by applying the genetic algorithm and the modal expansion method. The modal expansion method is used to estimate the vibration response of the whole structure. The genetic algorithm is used to estimate the optimal placement of vibration sensors. Optimal sensor placement can be obtained so that the fitness function is minimized in the genetic algorithm. This paper discusses the comparison of the performances of two types of fitness functions, modal assurance criteria(MAC) and condition number(CN). As a result, the estimation using MAC shows better performance than using CN.
정병규(Byung-Kyoo Jung),홍진숙(Chinsuk Hong),유정수(Jungsoo Ryue),정의봉(Weui-Bong Jeong),신구균(Ku-Kyun Shin) 한국소음진동공학회 2015 한국소음진동공학회 논문집 Vol.25 No.8
This paper deals with the dispersion relation of the waves sustained in a cylindrical shell submerged in the fluid. The waveguide finite method and the boundary element method are used to predict the dispersion characteristic of the cylindrical shell. The dispersion diagram of the cylinder is estimated from the eigenvalue problem and the forced vibration response. It follows that the water- loading leads to the decrease of the cut-on frequencies and the phase speeds of the bending waves. On the contrary, the longitudinal waves and the torsional waves are hardly affected by the fluid, and therefore the order of the cut-on frequencies of the waves is changed. The acoustic dispersion diagram is also estimated from the forced acoustic response to identify the characteristics of the wave radiated to the fluid. It follows that the acoustic waves on and near the surface of the cylinder are the same as those in the structure. But at the far field the acoustic waves caused by subsonic waves e.g., the bending waves disappear as the increase of the distance. Conclusively, the characteristics of waves in cylindrical shells are significantly affected by water-loading in terms of the cut-on frequency, the wave speed, the order of the cut-on and radiation.
정병규(Byung-Kyoo Jung),정의봉(Weui-Bong Jeong),조대승(Dae-Seung Cho),김국현(Kookhyun Kim),강명환(Myeonghwan Kang) 한국소음진동공학회 2014 한국소음진동공학회 논문집 Vol.24 No.5
This study is concerned with the estimation of vibration-field of a cylindrical structure by modal expansion method(MEM). MEM is a technique that identifies modal participation factors using some of vibration signals and natural modes of the structure: The selection of sensor locations has a big influence on predicted vibration results. Therefore, this paper deals with four optimal sensor placement(OSP) methods, EFI, EFI-DPR, EVP, AutoMAC, for the estimation of vibration field. It also finds optimal sensor locations of the cylindrical structure by each OSP method and then performs MEMs. Predicted vibration results compared with reference ones obtained by forced response analysis. The standard deviations of errors between reference and predicted results were also calculated. It is utilized to select the most suitable OSP method for estimation of vibration field of the cylindrical structure.
가속도 측정신호를 이용한 냉장고 홴의 진동원과 방사소음의 예측
정병규(Jung, Byung-Kyoo),정의봉(Jeong, Weui-Bong) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.9
Obtaining the real exciting force is important for the analysis of structural vibration or sound radiation to represent the actual condition. But in most cases, it is so difficult to get the actual force signals by direct measurement using sensors due to complex geometry. This paper suggests advanced source identification method which can be applied to the prediction of radiated noise considering correlations between measured signals. This method was implemented to the identification of the fan force in the refrigerator. The analysis of structural vibration and radiated noise caused by the fan force was also performed. The comparison between predicted SPL and measured SPL of the radiated noise by the refrigerator fan showed good agreement.