• Title, Summary, Keyword: 크리로프 부공간

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Comparison of Projection-Based Model Order Reduction for Frequency Responses (주파수응답에 대한 투영기반 모델차수축소법의 비교)

  • Won, Bo Reum;Han, Jeong Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.9
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    • pp.933-941
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    • 2014
  • This paper provides a comparison between the Krylov subspace method (KSM) and modal truncation method (MTM), which are typical projection-based model order reduction methods. The frequency responses are compared to determine the numerical accuracies and efficiencies. In order to compare the numerical accuracies of the KSM and MTM, the frequency responses and relative errors according to the order of the reduced model and frequency of interest are studied. Subsequently, a numerical examination shows whether a reduced order can be determined automatically with the help of an error convergence indicator. As for the numerical efficiency, the computation time needed to generate the projection matrix and the solution time to perform a frequency response analysis are compared according to the reduced order. A finite element model for a car suspension is considered as an application example of the numerical comparison.

Frequency Response Analysis of Array-Type MEMS Resonators by Model Order Reduction Using Krylov Subspace Method (크리로프 부공간법에 근거한 모델차수축소기법을 통한 배열형 MEMS 공진기의 주파수응답해석)

  • Han, Jeong-Sam;Ko, Jin-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.9
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    • pp.878-885
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    • 2009
  • One of important factors in designing MEMS resonators for RF filters is obtaining a desired frequency response function (FRF) within a specific frequency range of interest. Because various array-type MEMS resonators have been recently introduced to improve the filter characteristics such as bandwidth, pass-band, and shape factor, the degrees of freedom (DOF) of finite elements for their FRF calculation dramatically increases and therefore raises computational difficulties. In this paper the Krylov subspace-based model order reduction using moment-matching with non-zero expansion points is represented as a numerical solution to perform the frequency response analyses of those array-type MEMS resonators in an efficient way. By matching moments at a frequency around the specific operation range of the array-type resonators, the required FRF can be efficiently calculated regardless of their operating frequency from significantly reduced systems. In addition, because of the characteristics of the moment-matching method, a minimal order of reduced system with a prearranged accuracy can be determined through an error indicator using successive reduced models, which is very useful to automate the order reduction process and FRF calculation for structural optimization iterations. We also found out that the presented method could obtain the FRF of a $6\times6$ array-type resonator within a seventieth of the computational time necessary for the direct method and in addition FRF calculation by the mode superposition method could not even be completed because of a data overflow with a half after calculation of 9,722 eigenmodes.

Efficient Modal Analysis of Prestressed Structures via Model Order Reduction (모델차수축소법을 이용한 프리스트레스 구조물의 효율적인 고유진동해석)

  • Han, Jeong-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.10
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    • pp.1211-1222
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    • 2011
  • It is necessary to use prestressed modal analysis to calculate the modal frequencies and mode shapes of a prestressed structure such as a spinning blade, a preloaded structure, or a thermally deformed pipe, because the prestress effect sometimes causes significant changes in the frequencies and mode shapes. When the finite element model under consideration has a very large number of degrees of freedom, repeated prestressed modal analyses for investigating the prestress effects might become too computationally expensive to finish within a reasonable design-process time. To alleviate these computational difficulties, a Krylov subspace-based model order reduction, which reduces the number of degrees of freedom of the original finite element model and speeds up the necessary prestressed modal analysis with the reduced order models (ROMs), is presented. The numerical process for the moment-matching model reduction is performed directly on the full order models (FOMs) (modeled in ANSYS) by the Arnoldi process. To demonstrate the advantages of this approach for performing prestressed modal analysis, the prestressed wheel and the compressor impeller under their high-speed rotation are considered as examples.

Model Order Reduction Using Moment-Matching Method Based on Krylov Subspace and Its Application to FRF Calculation for Array-Type MEMS Resonators (Krylov 부공간에 근거한 모멘트일치법을 이용한 모델차수축소법 및 배열형 MEMS 공진기 주파수응답함수 계산에의 응용)

  • Han, Jeong-Sam;Ko, Jin-Hwan
    • Proceedings of the KSME Conference
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    • pp.436-441
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    • 2008
  • One of important factors in designing array-type MEMS resonators is obtaining a desired frequency response function (FRF) within a specific range. In this paper Krylov subspace-based model order reduction using moment-matching with non-zero expansion points is represented to calculate the FRF of array-type resonators. By matching moments at a frequency around a specific range of the array-type resonators, required FRFs can be efficiently calculated with significantly reduced systems regardless of their operating frequencies. In addition, because of the characteristics of moment-matching method, a minimal order of reduced system with a specified accuracy can be determined through an error indicator using successive reduced models, which is very useful to automate the order reduction process and FRF calculation for structural optimization iterations.

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Eigenvalue and Frequency Response Analyses of a Hard Disk Drive Actuator Using Reduced Finite Element Models (축소된 유한요소모델을 이용한 하드디스크 구동부의 고유치 및 주파수응답 해석)

  • Han, Jeong-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.5
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    • pp.541-549
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    • 2007
  • In the case of control for mechanical systems, it is highly useful to be able to provide a compact model of the mechanical system to control engineers using the smallest number of state variables, while still providing an accurate model. The reduced mechanical model can then be inserted into the complete system models and used for extended system-level dynamic simulation. In this paper, moment-matching based model order reductions (MOR) using Krylov subspaces, which reduce the number of degrees of freedom of an original finite element model via the Arnoldi process, are presented to study the eigenvalue and frequency response problems of a HDD actuator and suspension system.

Efficient Vibration Simulation Using Model Order Reduction (모델차수축소법을 이용한 효율적인 진동해석)

  • Han Jeong-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.3
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    • pp.310-317
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    • 2006
  • Currently most practical vibration and structural problems in automotive suspensions require the use of the finite element method to obtain their structural responses. When the finite element model has a very large number of degrees of freedom the harmonic and dynamic analyses are computationally too expensive to repeat within a feasible design process time. To alleviate the computational difficulty, this paper presents a moment-matching based model order reduction (MOR) which reduces the number of degrees of freedom of the original finite element model and speeds up the necessary simulations with the reduced-size models. The moment-matching model reduction via the Arnoldi process is performed directly to ANSYS finite element models by software mor4ansys. Among automotive suspension components, a knuckle is taken as an example to demonstrate the advantages of this approach for vibration simulation. The frequency and transient dynamic responses by the MOR are compared with those by the mode superposition method.

Model Order Reduction for Piezoelectric-Structural Systems with Coriolis Effect (코리올리 효과를 가진 압전-구조계의 모델차수축소법)

  • Han, Jeong-Sam
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.713-716
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    • 2010
  • 본 논문에서는 코리올리 효과를 가진 압전-구조 시스템의 주파수응답 해석을 효율적으로 수행하기 위한 크리로프 부공간 모델차수축소법을 제안하였다. 이 방법은 초기 유한요소모델과 축소모델의 전달함수의 계수인 모멘트를 일치시키는 방법을 이용하는 축소기법으로 이미 대형 유한요소모델의 주파수응답 해석에 효과적으로 이용되고 있다. 예제로 고려된 압전형 미소 각속도계의 해석에는 압전구동 하중과 구조체의 회전에 따른 원심력이 동시에 입력하중으로 고려되는 다중입력의 경우이므로 변환행렬 V의 생성시, block Arnoldi 과정을 이용하여 두 하중의 효과를 축소모델에 함께 고려한다. 본 문제에 제안된 축소기법을 이용한 결과, 축소모델을 이용하여 원래 시스템의 관심영역의 주파수응답을 작은 차수의 모델로도 정확하게 계산할 수 있음을 확인하였다. 본 논문에서 제안된 방법을 이용하면 다양한 가진조건과 각속도 입력 하에서의 주파수응답을 정확하고 더욱 효율적으로 계산할 수 있을 것이다.

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