• Title/Summary/Keyword: Rigid Body Mode

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A Refined Semi-Analytic Sensitivity Study Based on the Mode Decomposition and Neumann Series Expansion (I) - Static Problem - (강체모드분리와 급수전개를 통한 준해석적 민감도 계산 방법의 개선에 관한 연구(I) - 정적 문제 -)

  • Cho, Maeng-Hyo;Kim, Hyun-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.4
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    • pp.585-592
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    • 2003
  • Among various sensitivity evaluation techniques, semi-analytical method(SAM) is quite popular since this method is more advantageous than analytical method(AM) and global finite difference method(FDM). However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified fur individual elements. Such errors result from the numerical differentiation of the pseudo load vector calculated by the finite difference scheme. In the present study, an iterative method combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes and the error of SAM caused by numerical difference scheme is alleviated by using a Von Neumann series approximation considering the higher order terms for the sensitivity derivatives.

A Refined Semi-Analytic Sensitivity Study Based on the Mode Decomposition and Neumann Series Expansion in Eigenvalue Problem(II) - Eigenvalue Problem - (강체모드분리와 급수전개를 통한 고유치 문제에서의 준해석적 설계 민감도 개선에 관한 연구(II) -동적 문제 -)

  • Kim, Hyun-Gi;Cho, Maeng-Hyo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.4
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    • pp.593-600
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    • 2003
  • Structural optimization often requires the evaluation of design sensitivities. The Semi Analytic Method(SAM) fur computing sensitivity is popular in shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements. the SAM shows severe inaccuracy. In this study, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover. the error of the SAM caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms. Finally the present study shows that the refined SAM including the iterative method improves the results of sensitivity analysis in dynamic problems.

Vibration Mode of the Drivesystem Considered the Vehicle Body's Dynamic Characteristics (차체의 동특성을 고려한 구동시스템의 진동모드)

  • 유충준
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.148-159
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    • 2004
  • This paper discusses vibration mode of the drivesystem considered the vehicle body's dynamic characteristics to study the influence of the vehicle body's dynamic characteristics on the vibration mode of the engine mount system and the ride quality of a vehicle. The simulation model consists of the engine mount system, the powertrain and the rigid or elastic vehicle body. Variables used in this study are the stiffnesses of an engine mount system and the excitation forces. The Goals of the study are analyzing both the vibration transmitted to the vehicle body including the drivesystem and the influence of the vehicle body's dynamic characteristics on the engine mount system. The mode of drivesystems with a rigid and a elastic vehicle body was compared. From the result of the forced vibration analysis for the drivesystem with a elastic vehicle body, it is shown that the vehicle body's dynamic characteristics influence on the engine mount system reciprocally.

A REFINED SEMI-ANALYTIC DESIGN SENSITIVITIES BASED ON MODE DECOMPOSITION AND NEUMANN SERIES IN REDUCED SYSTEM (축소모델에서 강체모드 분리와 급수전개를 통한 준해석적 민감도 계산 방법)

  • Kim, Hyun-Gi;Cho, Maeng-Hyo
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.491-496
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    • 2003
  • In sensitivity analysis, semi-analytical method(SAM) reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Recently such errors of SAM resulted by the finite difference scheme have been improved by the separation of rigid body mode. But the eigenvalue should be obtained first before the sensitivity analysis is performed and it takes much time in the case that large system is considered. In the present study, by constructing a reduced one from the original system, iterative method combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The sensitivity analysis is performed by the eigenvector acquired from the reduced system. The error of SAM caused by difference scheme is alleviated by Von Neumann series approximation.

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Optimum Design of Engine Mount System Considering Body Flexibility (차체의 유연성을 고려한 엔진마운트 최적설계)

  • 황인수;김태욱;박우선;고병식
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.10a
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    • pp.319-325
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    • 1997
  • As customer's demand for vehicle comfort is getting increased, vibration problem is very important issue in vehicle development. Engine is the main factor causing vehicle vibration, so that we should isolate detrimental transmitted excitation from engine. In order to solve this problem engine mounting system was properly optimized. Simulation was performed not only rigid body mode analysis but also flexible body mode analysis. We obtained the optimal locations and stiffness of engine mounts from simulation results, and had reasonable results from considering flexible body mode than only rigid body mode analysis.

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Dynamic Modeling Method for Beams Undergoing Overall Rigid Body Motion Considering Two Geometric Non-linear Effects (두 기하학적 비선형 효과들을 고려한 대변위 강체운동을 하는 보의 동적 모델링 방법)

  • Kim, Na-Eun;Yoo, Hong-Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.6
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    • pp.1014-1019
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    • 2003
  • A dynamic modeling method for beams undergoing overall rigid body motion is presented in this paper. Two special deformation variables are introduced to represent the stretching and the curvature and are approximated by the assumed mode method. Geometric constraint equations that relate the two special deformation variables and the cartesian deformation variables are incorporated into the modeling method. By using the special deformation variables, all natural as well as geometric boundary conditions can be satisfied. It is shown that the geometric nonlinear effects of stretching and curvature play important roles to accurately predict the dynamic response when overall rigid body motion is involved.

The calculation of refined semi-analytic sensitivity based on the hybrid element (혼합 요소에서의 개선된 민감도 계산법)

  • Cho, Maeng-Hyo;Kim, Hyun-Gi
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.686-691
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    • 2001
  • Structural optimization often require the evaluation of design sensitivities. The Semi Analytic method(SAM) is popular for shape optimization because this method has several advantages. But when relatively large rigid body motions are identified for individual elements, the SA method shows severe inaccuracy. In this paper, the improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes. Moreover, the error of the SA method caused by numerical difference scheme is alleviated by using a series approximation for the sensitivity derivatives and considering the higher order terms.

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A New Method of Collision Mode Evolution for Three-Dimensional Rigid Body Impact With Friction

  • Park, Jong-Hoon;Chung, Wan-Kyun;Youm, Young-Il
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.1769-1775
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    • 2004
  • In presence of collision between two rigid bodies, they exhibit impulsive behavior to generate physically feasible state. When the frictional impulse is involved, collision resolution can not be easily made based on a simple Newton's law or Poisson's law, mainly due to possible change of collision mode during collision, For example, sliding may change to sticking, and then sliding resumes. We first examine two conventional methods: the method of mode evolution by differential equation, and the other by linear complementarity programming. Then, we propose a new method for mode evolution by solving only algebraic equations defining mode changes. Further, our method attains the original nonlinear impulse cone constraint. The numerical simulation will elucidate the advantage of the proposed method as an alternative to conventional ones.

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Enhanced generalized modeling method for compliant mechanisms: Multi-Compliant-Body matrix method

  • Lim, Hyunho;Choi, Young-Man
    • Structural Engineering and Mechanics
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    • v.82 no.4
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    • pp.503-515
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    • 2022
  • The multi-rigid-body matrix method (MRBMM) is a generalized modeling method for obtaining the displacements, forces, and dynamic characteristics of a compliant mechanism without performing inner-force analysis. The method discretizes a compliant mechanism of any type into flexure hinges and rigid bodies by implementing a multi-body mass-spring model using coordinate transformations in a matrix form. However, in this method, the deformations of bodies that are assumed to be rigid are inherently omitted. Consequently, it may yield erroneous results in certain mechanisms. In this paper, we present a multi-compliant-body matrix-method (MCBMM) that considers a rigid body as a compliant element, while retaining the generalized framework of the MRBMM. In the MCBMM, a rigid body in the MRBMM is segmented into a certain number of body nodes and flexure hinges. The proposed method was verified using two examples: the first (an XY positioning stage) demonstrated that the MCBMM outperforms the MRBMM in estimating the static deformation and dynamic mode. In the second example (a bridge-type displacement amplification mechanism), the MCBMM estimated the displacement amplification ratio more accurately than several previously proposed modeling methods.

Dynamic Analysis of a Cantilever Beam Undertaking Impulsive Force That Undergoes Rigid Body Motion (강체 운동을 고려한 충격을 받는 외팔 보의 동적 해석)

  • Lim, Hong-Seok;Yoo, Hong-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.890-895
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    • 2005
  • This paper presents the dynamic analysis of a cantilever beam undertaking impulsive force that undergoes rigid body motion. The transient response of the beam induced by the impulsive force and the rigid body motion is calculated based on hybrid deformation variable modeling method by applying the Rayleigh-Ritz assumed mode method. The stiffness variation effect caused by the rigid body motion is considered in this modeling. The effects of the impulsive force position and the angular velocity on the transient responses of the beam are investigated through numerical studies.

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