• Title/Summary/Keyword: Dynamic coordinate system

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Analysis and Control of the Flexible Multibody System Using MATLAB (MATLAB을 이용한 유연 다물체 시스템의 해석 및 제어)

  • Jung, Sung-Pil;Park, Tae-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.5
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    • pp.437-443
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    • 2008
  • In this paper, analysis and control of the flexible multibody system using MATLAB is presented. The equations of motion of a flexible body are derived in terms of the modal coordinate. The rigid-flexible multibody dynamic solver is developed. Finite element information required to analyze motion of flexible bodies is imported from ANSYS. The modified finite element data, such as modal mass matrix, modal stiffness matrix and constraint mode shapes, is calculated in the solver. Since the solver is developed using MATLAB, it is very easy to connect with SIMULINK which is widely used to control motion of the multibody system. Several simulations are implemented to verify the developed solver. A control example is carried out and the usefulness of the developed solver is demonstrated.

Robust stabilization of nonlinear uncertain systems without matching conditions (정합조건을 만족하지 않는 불확정 비선형 시스템의 강인 안정화)

  • 주진만;최윤호;박진배
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.159-162
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    • 1997
  • This paper describes robust stabilization of nonlinear single-input uncertain systems without matching conditions. We consider nonlinear systems with a vector of unknown constant parameters perturbed about a known value. The approach utilizes the generalized controller canonical form to lump the unmatched uncertainties recursively into the matched ones. This can be achieved via nonlinear coordinate transformations which depend not only on the states of the nonlinear system but also on the control input. Then the dynamic robust control law is derived and the stability result is also presented.

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Dynamic Characteristics of HDD Slider by Perturbated Direct Numerical Method

  • Khan Polina V.;Hwang Pyung
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2003.11a
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    • pp.210-214
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    • 2003
  • The static and dynamic characteristics of HDD slider with ulta-low flying height are analyzed using Direct Numerical method with Boundary Fitted Coordinate System. The slip flow effect is considered using the Boltzmann equation solution in a form of the flow rate database. The air film stiffness and damping are evaluated by the small perturbation method.

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Dynamic Stress Analysis of Flexible Multibody using DADS (DADS를 이용한 유연 다물체의 동응력 해석)

  • Ahn, K.W.;Seo, K.H.;Hwang, W.G.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.107-112
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    • 1998
  • A great deal of time and effort are required to evaluate the safety and durability of a vehicle structure in the vehicle development stage. It is difficult to find the reasons for cracks which occur in the body and frame of a vehicle during tests. Recently computer aided engineering techniques have been utilized to solve the problems of safety and durability of vehicles. In this study, a dynamic stress analysis is performed on the frame of the vehicle by rigid and flexible multibody dynamics techniques. The result of the analysis is compared to that of the actual test. The full vehicle dynamic models for the rigid and flexible bodies are developed by DADS package. The modal coordinate system is used to save time for the dynamic stress analysis. The flexible multibody dynamic models have 12 normal modes considering the flexibility of the frame. Dynamic stresses arc calculated by relating the stress influence coefficients and the applied forces.

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The G. D. Q. method for the harmonic dynamic analysis of rotational shell structural elements

  • Viola, Erasmo;Artioli, Edoardo
    • Structural Engineering and Mechanics
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    • v.17 no.6
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    • pp.789-817
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    • 2004
  • This paper deals with the modal analysis of rotational shell structures by means of the numerical solution technique known as the Generalized Differential Quadrature (G. D. Q.) method. The treatment is conducted within the Reissner first order shear deformation theory (F. S. D. T.) for linearly elastic isotropic shells. Starting from a non-linear formulation, the compatibility equations via Principle of Virtual Works are obtained, for the general shell structure, given the internal equilibrium equations in terms of stress resultants and couples. These equations are subsequently linearized and specialized for the rotational geometry, expanding all problem variables in a partial Fourier series, with respect to the longitudinal coordinate. The procedure leads to the fundamental system of dynamic equilibrium equations in terms of the reference surface kinematic harmonic components. Finally, a one-dimensional problem, by means of a set of five ordinary differential equations, in which the only spatial coordinate appearing is the one along meridians, is obtained. This can be conveniently solved using an appropriate G. D. Q. method in meridional direction, yielding accurate results with an extremely low computational cost and not using the so-called "delta-point" technique.

An Assembly Modeling System for Dynamic and Kinematic Analysis (동역학 및 기구학적 해석을 위한 조립체 모델링 시스템)

  • 김성환;이건우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.48-58
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    • 1989
  • An assembly modeling system, with which a designer can interactively create an assembly of components ready for the dynamic analysis, has been developed. In this system, an assembly model is created from the mating conditions between the components in the assembly, and then most information required for the dynamic or kinematic analysis packages are derived. For this development, the following problems have been solved; the creation of assembly data structure, the derivation of the joint information, the inference of each component's position, and the creation of the joint coordinate systems. Through this work, the designer can easily model an assembly by assigning mating conditions, and check the dynamic or kinematic performance with the automatic creation of inputs for the assembly analysis packages.

Design of Reconfigurable Flight Control Law Using Neural Networks (신경회로망을 이용한 재형상 비행제어법칙 설계)

  • 김부민;김병수;김응태;박무혁
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.7
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    • pp.35-44
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    • 2006
  • When control surface failure occurs, it is conventional to correct a current control or to transform to other control. In this paper, instead of adopting a conventional way, a reconfiguration method which compensate the failure with alternative control surface deflection, depending on the level of failure, by using neural network and PCH(Pseudo-Control Hedging). The Conroller is designed of inner-loop(SCAS : Stability Command Augmentation System) with DMI(Dynamic Model Inversion) and outer-loop with Y axis acceleration feedback for a coordinate turn. Additionally, double PCH method was adopted to prevent actuator saturation and input command was generated to compensate for failure. At the end, The feasibility of the method is validated with randomly selected failure scenarios.

A Non-recursive Formulation of Dynamic Force Analysis in Recursive Multibody Dynamics (순환 다물체동역학에서의 비순환적인 동하중해석 공식)

  • Kim, Seong-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.5
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    • pp.809-818
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    • 1997
  • An efficient non-recursive formulation of dynamic force analysis has been developed for serially connected multibody systems. Although derivation of equations of motion is based on a recursive dynamic formulation with joint relative coordinates, in the proposed formulation, dynamic forces such as joint reaction forces and driving force are computed non-recursively for specified joints. The efficiency of the proposed formulation has been proved by the operational count and the CPU time measure, comparing with that of the conventional recursive Newton-Euler formulation. A simulation of 7-DOF RRC robot arm has been carried out to validate solutions of reaction forces by comparing with those from a commercial dynamic analysis program DADS.

An Empirical Investigation on Dynamic Relationships among For-profit Hospital, Healthcare Industry, National Medical Spending (의료산업화에 따른 의료비상승의 변화 메커니즘 : 병원의 영리화 & 의료의 산업화와 의료비의 영향에 대해서)

  • Yoon, In-Mo;Kim, Ki-Chan
    • Korean System Dynamics Review
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    • v.9 no.1
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    • pp.93-105
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    • 2008
  • This study suggests a Causal Loop Diagram(CLD) of Causality Mechanism which are intergrating matter of for-profit hospital, non-for profit hospital, healthcare development, national medical spending. To coordinate each part theory, we suggest more developed medical system in our study. Through the system thinking, development of hospital as research center in industry can lesson the rise of medical spending effectively.

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Analytical solutions for skewed thick plates subjected to transverse loading

  • Chun, Pang-Jo;Fu, Gongkang;Lim, Yun Mook
    • Structural Engineering and Mechanics
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    • v.38 no.5
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    • pp.549-571
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    • 2011
  • This paper presents analytical solutions for skewed thick plates under transverse loading that have previously been unreported in the literature. The thick plate solution is obtained in a framework of an oblique coordinate system. The governing equation is first derived in the oblique coordinate system, and the solution is obtained using deflection and rotation as partial derivatives of a potential function developed in this research. The solution technique is applied to three illustrative application examples, and the results are compared with numerical solutions in the literature and those derived from the commercial finite element analysis package ANSYS 11. These results are in excellent agreement. The present solution may also be used to model skewed structures such as skewed bridges, to facilitate efficient routine design or evaluation analyses, and to form special elements for finite element analysis. At the same time, the analytical solution developed in this research could be used to develop methods to address post-buckling and dynamic problems.