• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.8 s.227
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• pp.1212-1220
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• 2004

The structural unbalance mass and laundry are the important sources of the severe vibrations of automatic washing machines. In this paper, a mathematical model is developed for the dynamic analysis of the vertical axis automatic washing machines of pulsator-type. In the model, the rigid body motion of tub assembly is represented by six degrees of freedom and the dynamics of automatic hydraulic balancer is represented by one degree of freedom. The fundamental elastic modes of the tub shell and four suspension bars are also taken into account in the mathematical model, based on analytical and experimental modal analysis results. The 12 degrees of freedom equations of motion are derived by using the Lagrange's equations and the present dynamic model is evaluated by comparing the numerical simulation results with experimentally measured data.

• Journal of KSNVE
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• v.9 no.3
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• pp.461-465
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• 1999

This paper presents theoretical analyses for unstable vibrations caused by the couple of bending and torsion in a rotating shaft driven through a universal joint. A driving shaft is assumed to be rigid and to rotate with a constant angular velocity. The driven shaft system consists of a flexible shaft with a circular section and a symmetrical rotor attached at a point between the shaft ends. Equations of motion derived hold with an accuracy of the second order of shaft deformations, and are analyzed by the asymptotic method. The vibrations become unstable when the driving shaft rotates with the angular velocity to be approximately equal to half of the sum of the natural frequencies for whirling and torsional vibrations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.563-567
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• 2000

This research is concerned with the dynamic modeling of solar arrays equipped with strain energy hinges(SEH). It is found from experiments that the SEH has nonlinear dynamic characteristics and complex buckling behavior, which is difficult to explain theoretically. In this paper, we use an equivalent one-dimensional nonlinear torsional spring for the SEH. Assuming that solar panels are rigid, we developed the systematic approach for the derivation of the theoretical model for the solar arrays equipped with the multitudes of the SEH. To this end, the kinematic relation of the displacement vector of each body is derived and then applied to the equations of motion. Lagrangian equations of motion are used for the derivations.

• Journal of Mechanical Science and Technology
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• v.19 no.spc1
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• pp.305-311
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• 2005

This research presents a three-dimensional modeling technique for a flexible sheet. A relative coordinate formulation is used to represent the kinematics of the sheet. The three-dimensional flexible sheet is modeled by multi-rigid bodies interconnected by out-of-plane joints and plate force elements. A parent node is designated as a master body and is connected to the ground by a floating joint to cover the rigid motion of the flexible sheet in space. Since the in-plane deformation of a sheet such as a paper and a film is relatively small, compared to out-of-plane deformation, only the out-of-plane deformation is accounted for in this research. The recursive formulation has been adopted to solve the equations of motion efficiently. An example is presented to show the validity of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.247-252
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• 2005

This research presents a three-dimensional modeling technique for a flexible sheet. A relative coordinate formulation is used to represent the kinematics of the sheet. The three-dimensional flexible sheet is modeled by multi-rigid bodies interconnected by out-of-plane joints and plate force elements. A parent node is designated as a master body and is connected to the ground by a floating joint to cover the rigid motion of the flexible sheet in space. Since the in-plane deformation of a sheet such as a paper and a film is relatively small, compared to out-of-plane deformation, only the out-of-plane deformation is accounted for in this research. The recursive formulation has been adopted to solve the equations of motion efficiently. An example is presented to show the validity of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1486-1497
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• 1996

The problem of determining the 3-demensional motion of any two rough bodies after a collision involves some rather long analysis and yet in some points it differs essentially from the corresponding problem in tdwo dimensions. We consider a special problem where two rough ellipsolids moving in any manner collide, and analyze the three dimensional impact process with Coulomb friction and Poisson's hypothesis. The differential equations that describe that process of the impact induce a flow in the tangent velocity space, the flow patterns characterize the possible impact cases. By using the graphic method in impulse space and numerical integration thchnique, we analyzed the impact process inall the possible cases and presented the algorithm for determining the post-impact motion. The principles could be applied to the general problem in three dimensions. We verified the effectiveness of the analysis results by simulating the numerous significant examples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.573-576
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• 2005

This research presents a three-dimensional modeling technique for a flexible sheet. A relative coordinate formulation is used to represent the kinematics of the sheet. The three-dimensional flexible sheet is modeled by multi-rigid bodies interconnected by out-of-plane joints and plate force elements. A parent node is designated as a master body and is connected to the ground by a floating joint to cover the rigid motion of the flexible sheet in space. Since the in-plane deformation of a sheet such as a paper and a film is relatively small, compared to out-of-plane deformation, only the out-of-plane deformation is accounted for in this research. The recursive formulation has been adopted to solve the equations of motion efficiently. An example is presented to show the validity of the proposed method.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.237-247
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• 1999

Flight parameters of a light aircraft in normal category named ChangGong-91 we identified from flight tests. Modified Maximum Likelihood Estimation (MMLE) is used to produce aerodynamic coefficients, stability and control derivatives. A Flight Training Device (FTD) has been developed based on the identified flight parameters. Flat earth, rigid body, and standard atmosphere are assumed in the FTD model. Euler angles are adapted for rotational state variables to reduce computational load. Variations in flight Mach number and Reynolds number are assumed to be negligible. Body, stability and inertial axes allow 6 second-order linear differential equations for translational and rotational motions. The equations of motion are integrated with respect to time, resulting in good agreements with flight tests.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.10-16
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• 2004

There are a lot of roots of errors in a motion of the optical pick-up actuator being one of the most significantcomponents in a CD-ROM drive. Most of the studios recently performed have a tendency to seek for the causes from an actuator itself. This paper presents dynamic characteristics of an actuator affected by the motion of a feeding deck. The feeding system is modeled as a rigid body with eight degree-of-freedom. Using Largrange's equation, we derive linear equations of motion with respect to the rectangular coordinate. We found that the ranges of the natural frequencies of a feeding deck and the actuator are close to each other. The time responses are also computed by the Newmark method and Runge-Kutta method. The result show that it is important effect to consider feeding deck in modeling and designing an optical pick-up.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.279-286
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• 1997

The objective of this paper is to investigate the effects of the rocking motion and the vertical natural frequency of a seismically isolated structure using LRBs. The governing equations of motion of the rigid body structure, which consider a large rocking motion, are derived. For the mathematical model of LRB, the horizontal stiffness equation based on Haringx's theory is used. From this paper, as decreasing the vertical natural frequency, the rocking responses increase and the horizontal isolation frequency and its earthquake responses are severely affected.