• Title, Summary, Keyword: 응답함수감도

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Model Updating Using Sensitivity of Frequency Response Function (주파수 응답함수의 감도를 이용한 모델개선법)

  • Kim, K.K.;Kim, Y.C.;Yang, B.S.;Kim, D.J.
    • Journal of Power System Engineering
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    • v.4 no.2
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    • pp.71-76
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    • 2000
  • It is well known that finite element analysis often has the inaccuracy when they are in conflict with test results. Model updating is concerned with the correction of analytical model by processing records of response from test results. This paper introduce a model updating technique using the frequency response function data. The measurement data is able to be used directly in the FRF sensitivity method because it is not necessary to identify. When a damping model is updated, it is necessary for the sensitivity matrix to be divided Into the complex part and real part. As an applying model, a cantilever and a rotor system are used. Specially the machined clearance($C_p$) of the journal bearing is updated.

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Design Sensitivity and Reliability Analysis of Plates (판구조물의 설계감도해석 및 신뢰성해석)

  • 김지호;양영순
    • Computational Structural Engineering
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    • v.4 no.4
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    • pp.125-133
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    • 1991
  • For the purpose of efficiently calculating the design sensitivity and the reliability for the complicated structures in which the structural responses or limit state functions are given by implicit form, the probabilistic finite element method is introduced to formulate the deterministic design sensitivity analysis method and incorporated with the second moment reliability methods such as MVFOSM, AFOSM and SORM. Also, the probabilistic design sensitivity analysis method needed in the reliability-based design is proposed. As numerical examples, two thin plates are analyzed for the cases of plane stress and plate bending. The initial yielding is defined as failure criterion, and applied loads, yield stress, plate thickness, Young's modulus and Poisson's ratio are treated as random variables. It is found that the response variances and the failure probabilities calculated by the proposed PFEM-based reliability method show good agreement with those by Monte Carlo simulation. The probabilistic design sensitivity evaluates explicitly the contribution of each random variable to probability of failure. Further, the design change can be evaluated without any difficulty, and their effect on reliability can be estimated quickly with high accuracy.

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Structural Dynamic Modification Using substructure Response Function Sensitivity Method(SRFSM) (부분구조응답함수감소법을 이용한 동적구조변경)

  • Ji, Tae-Han;Park, Yeong-Pil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.12
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    • pp.3782-3791
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    • 1996
  • A great deal of effert has been invested in upgrading the performance and the efficiency of mechanical structures. Using experimental modal analysis(EMA) or finite element analysis(FEA) data of mechanical structures, this performance and efficiency can be effectively evaluated. In order to analyze complex structures such as automobiles and aircraft, for the sake of computing efficiency, the dynamic substructuring techniques that allow to predict the dynamic behavior of a structure based on that of the composing structures, are widely used. By llinking a modal model obtained from EMA and an analytical model obtained from FEA, the best conditioned structures can be desinged. In this paper, a new algorithm for structural dynamic modification-SRFSM (substructure response function sensitivity method) is proposed by linking frequency responce function synthesis and response function sensitivity. A mehtod to obtain response function sensitivity using direct derivative of mechanical impedance, is also used.

The Time-Domain characteristics of Elliptic Filter Functions (Elliptic 필터 함수의 시간영역측성에 대한 고찰)

  • 한병성;김형갑
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.20 no.5
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    • pp.37-42
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    • 1983
  • The elliptic functions have transmission zeros on the imaginary axis and exhibit equal ripples in the stopband as well as in the passband. As a consequence they can be made optimal in the sense that the transition band is minimal. However the time domain behaviors turned out to be inferior to those of Chebyshev and Butterworth responses. This paper investigates the unit step responses and impulse responses in order to analyze the effects of various parameters such as passband attenuation, stopband frequencies M. etc., The following are the prominent features. Step responses of elliptic filters rise faster and produce larger overshoots and undershoots with higher natural frequencies. In the case of even functions, the initial values are non-zero which decreases as $\omega$s increases. Unlike Butter-worth or Chebyshev cases the impulse responses start with nonzero valses which also decrease as $\omega$s or order of the function increases. Eight figures are included to illustrate above analysis.

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Optimum Shape Design of a Rotating-Shaft Using ESO Method ESO 법을 이용한 회전축의 형상최적화

  • Yang, Bo-Suk;Kim, Yong-Han
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.360-364
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    • 2001
  • 본 논문에서는 최근의 진화적 구조최적화(ESO) 전략을 회전축의 형상최적화에 적용하였으며, 각 계산 스텝마다 단위 유한요소의 크기를 변경함으로써 기존의 방법보다 빠르고 정확한 최적형상에 수렴하는 새로운 방법을 제시하였다. 축요소의 직경을 시스템 설계변수로 하였으며, 축중량의 감소, 공진배율(Q-factor)의 감소 및 충분한 위험속도의 분리여유를 갖도록 목적함수를 설정하였다. 불평형응답 및 굽힙응력의 구속조건을 부가하였으며, 목적함수에 대한 설계변수의 감도해석을 수행하였다. 전동기축계에 대한 적용 결과로부터 주파수와 동적 구속조건하의 로터베어링 시스템에 대한 축 형상 최적화에 ESO법이 효과적으로 이용될 수 있음을 확인하였다.

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Application of Perturbation-based Sensitivity Analysis to Nuclear Characteristics (섭동론적 감도해석 이론의 원자로 핵특성에의 응용)

  • Byung Soo Lee;Mann Cho;Jeong Soo Han;Chung Hum Kim
    • Nuclear Engineering and Technology
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    • v.18 no.2
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    • pp.78-84
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    • 1986
  • An equation of material number density sensitivity coefficient is derived using first-order perturbation theory. The beginning of cycle of Super-Phenix I is taken as the reference system for this study. Effective multiplication factor of the reference system is defined as system response function and fuel enrichment and fuel effective density are chosen for the variation of reference input data since they are described by material number density which is a component of Boltzmann operator. The nuclear computational code system (KAERI-26 group cross section library/1DX/2DB/PERT-V) is employed for this calculation. Sensitivity coefficient of fuel enrichment on effective multiplication factor is 4.576 and sensitivity coefficient of effective fuel density on effective multiplication factor is 0.0756. This work shows that sensitivity methodology is lesser timeconsuming and gives more informations on important design parameters in comparison with the direct iterative calulation through large computer codes.

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Optical Fiber Filter Design Method Based on III Type Ladder Digital Filter (제 III 사다리형 디지털필터 형태의 광섬유필터 설계법)

  • 이채욱
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.11B
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    • pp.1903-1908
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    • 2000
  • 사다리형 디지털필터는 일반적으로 IIR 필터의 직접형, 병렬형 또는 종속형과 비교하여 주파수응답 감도가 뛰어나기 때문에 최근 많이 이용되고 있다. 사다리형 디지털필터는 모델의 형식에 따라 연분수 전개가 다르고 주어지는 전달함수에 따라 실현 가능한 형식과 불가능한 형식이 있다. 본 논문에서는 연분수 형태의 제 III 사다리형 디지털필터를 모델로 하여 방형성 결합기와 광섬유를 이용한 사다리형 광섬유필터의 실현조건과 설계방법을 논하였다.

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Updating Algorithms of Finite Element Model Using Singular Value Decomposition and Eigenanalysis (특이값 분해와 고유치해석을 이용한 유한요소모델의 개선)

  • 김홍준;박영필
    • Journal of KSNVE
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    • v.9 no.1
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    • pp.163-173
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    • 1999
  • Precise and reasonable modelling is necessary and indispensable to the analysis of dynamic characteristics of mechanical structures. Also. the effective prediction of the change of modal properties due to the variation of design parameters is required especially for the application of finite element method to the structural dynamics problems. To meet those necessity and requirement, three model updating algorithms are proposed for finite element methods. Those algorithms are based on sensitivity analysis of the modal data obtained from experimental modal analysis(EMA) and analytical modal analysis(AMA). The adapted sensitivity analysis methods of the algorithms are 1)eigensensitivity(EGNS) method. 2)frequency response function sensitivity(FRFS) method. 3)sensitivity based element-by-element method (SBEEM), Singular value decomposition(SVD) is used for performing eigenanalysis and parameter estimation in the updating process. Those algorithms are applied to finite element of a plate and the updating capability of each algorithm is compared in terms of accuracy. reliability and stability of the updating process. It is shown that the model updating method using frequency response function is superior to the other methods in view of various updating capabilities.

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$H^{\infty}$ Speed Control for Hot Rolling Mill Drives using Mixed Sensitivity Minimization (혼합감도최소화를 이용한 열간압연 구동기에 대한 $H^{\infty}$ 속도제어)

  • Kim, Jong-Hae;Um, Tae-Ho;Park, Hong-Bae;Lee, Sang-Ho;Jeong, Jin-Yang;Lee, Joo-Kang
    • Journal of Institute of Control, Robotics and Systems
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    • v.4 no.1
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    • pp.134-140
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    • 1998
  • 포항제철 2열연공장의 사상압연에 사용되고 있는 DC 모터를 가지는 열간압연 구동기에 대한 견실 H/sup .inf./ 속도제어기 설계방법을 제안한다. 기존에는 PI 재어기법을 이용하여 속도를 제어하고 있으므로 불확실성과 외란등이 존재할 경우 양호한 제어 성능을 얻기 힘들다. 이를 해결하기 위해 주파수 하중 함수를 가지는 혼합감도최소화 문제를 설정하여 견실성을 보장하는 H/sup .inf./ 속도제어기를 설계한다. 이때 주파수 하중함수는 루프쉐이핑기법을 이용하여 주어진 구동기 플랜트에 적합하도록 선택한다. H/sup .inf./ 속도제어기 설계는 Pasek이 제시한 DC 모터의 모델링 방법에 의해 얻어진 모델을 포함하는 구동기 모델에서 속도제어기 부분을 제외한 모델을 대상으로 한다. 제안한 견실 속도제어기 설계방법은 파라미터 변화나 부하토크 변동 등의 외란에 대하여 폐루프 시스템의 견실안정성과 원하는 속도에 좋은 추적 성능을 보인다. 제어 대상인 포항제철 2열연공장의 열간압연 구동기에 대한 시뮬레이션을 통해 기준속도 추적성, 응답속도, 불확실성과 외란에 대한 견실성 등의 성능에 기존의 PI 속도제어기보다 양호함을 확인함으로써 제안한 견실 H/sup .inf./ 속도제어기 설계 방법의 타당성을 보인다.

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A Study on the Quality Deviation of Passenger Cars using the Robust Design (강건 설계 기법을 이용한 승용차의 품질 산포에 관한 연구)

  • Kim, Ki-Chang;Kim, Chan-Mook
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.110-113
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    • 2006
  • This paper describes the development process of body and full vehicle for reduced idle vibration through the data level of frequency and sensitivity. The vibration mode map is used to separate body structure modes from resonance of engine idle nm and steering system. This paper describes the analysis approach process to reduce the variation of uncertainties for idle vibration performance at initial design stage. The robust design method is performed to increase the stabilization performance under vehicle vibration. It is used to predict the effects of the stiffness deviation according to the spot welding condition of the body structure. The tolerance associated with hood over slam bumper is analyzed for the quality deviation of the moving system in full vehicle. And the glass sealant stiffness and weight difference is considered for the deviation characteristic. The design guideline is suggested considering sensitivity about body and full vehicle by using mother car at initial design stage. It makes possible to design the good NVH performance and save vehicles to be used in tests. These improvements can lead to shortening the time needed to develop better vehicles.

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