• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.874-880
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• 2015

This paper presents the vibration analysis of a deploying beam with spin when the beam has a time-dependent spinning speed. In the previous studies for the deploying beams with spin, the spinning speed was time-independent. However, it is more reasonable to consider the time-dependent spinning speed. The present study introduces the time-dependent spinning speed in the modeling. The Euler-Bernoulli beam theory and von Karman nonlinear strain theory are used together to derive the equations of motion. After the equations of motion are transformed into the weak forms, the weak forms are discretized. The natural frequency and dynamic response are obtained. The effect of the time-dependent spinning speed on the dynamic response is studied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.348-353
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• 2008

A vibration analysis for a rotating cantilever beam with the tapered cross section is presented in this study. The stiffness changes due to the stretching caused by centrifugal inertia forces when a tapered cantilever beam rotates about the axis perpendicular to its longitudinal axis. When the cross section of cantilever beam are assumed to decrease constantly, the mass and stiffness also change according to the variation of the thickness and width ratio of a tapered cantilever beam. Such phenomena result in variations of natural frequencies and mode shapes. Therefore it is important to the equations of motion in order to be obtained accurate predictions of these variations. The equations of motion of a rotating tapered cantilever beam are derived by using hybrid deformation variable modeling method and numerical results are obtained along with the angular velocity and the thickness and width ratio.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.3
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• pp.133-140
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• 1993

In this paper, we prpose a method for tracking optimally a spatial trajectory of the end-effector of flexible robot arms with multiple joints. The proposed method finds joint trajectories and joint torques necessary to produce the desired end-effector motion of flexible manipulator. In inverse kinematics, optimized joint trajectories are computed from elastic equations. In inverse dynamics, joint torques are obtained from the joint euqations by using the optimized joint trajectories. The equations of motion using finite element method and virtual work principle are employed. Optimal control is applied to optimize joint trajectories which are computed in inverse kinematics. The simulation result of a flexible planar manipulator is presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.155-159
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• 1991

This paper is a study on the Inverse dynamics of a one-1ink flexible robot arm which is control led by the transiational base motion. The system is composed of the flexible arm, the mobil stage, a DC servomotor, and a computer. The arm base is shifted so that the tip follows a desired path function. The tip Rotten is measured by the laser displacement sensor. The governing equations are based on the Bernoullie-Euler beam theory and solved by applying the Laplace transform method and then the numerical inversion method to the resulted equations. Tip responses obtained both theoretically and experimentally are in good agreement with the desired trajectory, which shows that the scheme of inverse dynamics is effective for the open-loop endpoint positioning of the flexible am driven by the translation stage.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.1
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• pp.25-34
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• 2018

In this study, the behavior of the coupled mooring system and floating body is analyzed. The related works are introduced for the mooring analysis of the floating body. Equations motion are introduced for calculating mooring force connected with the floating body. For formulating the equations of motion, the concept of the constrained force is applied for compact expression of it. The input and output data of the module for calculating mooring force is defined. The static analysis and quasi-static analysis are performed. For the analysis, equilibrium equation for elastic catenary mooring line is used by employing finite element method, and the C# solver is developed in this research. The analysis results are validated by comparing with other research results.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.731-736
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• 2017

Friction Pendulum isolators are tools developed in the past few decades. The simplest form of these isolators, are FPS whose main disadvantages are having a constant frequency independent of the frequency of the structure. For this reason, researchers have invented VFPI isolator whose frequency is variable and depends on displacement. Another friction pendulum isolator is DCFP isolator which is a combination of two FPS isolators. In this article, first by changing the geometry of DCFP isolator plates from spherical to elliptical, the motion and frequency equations of DVFPI isolators are defined, and then the seismic behavior of DVFPI isolators are analyzed in various geometric and plate friction settings using motion equations, and confirmed using ABAQUS software. The most important results of this study are that the hysteresis behavior of DVFPI isolators are severely nonlinear, its curve follows two distinct curvatures, and that the restoring force is faced with softening mechanism that limits the seismic force transmitted to the structure, whereas the restoring force in DCFP isolators increases linearly with increasing displacement.

• Smart Structures and Systems
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• v.19 no.6
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• pp.695-703
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• 2017

In this paper, based on first-order shear deformation theory, the governing equations of motion for a sandwich curved beam including an elastic core and two piezo-magnetic face-sheets are presented. The curved beam model is resting on Pasternak's foundation and subjected to applied electric and magnetic potentials on the piezo-magnetic face-sheets and transverse loading. The five equations of motion are analytically solved and the bending and vibration results are obtained. The influence of important parameters of the model such as direct and shear parameters of foundation and applied electric and magnetic potentials are studied on the electro-mechanical responses of the problem. A comparison with literatures was performed to validate our formulation and results.

• Journal of Astronomy and Space Sciences
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• v.25 no.3
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• pp.255-266
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• 2008

The current paper presents application of a new analytic solution in general relative motion to spacecraft formation flying in an elliptic orbit. The calculus of variations is used to analytically find optimal trajectories and controls for the given problem. The inverse of the fundamental matrix associated with the dynamic equations is not required for the solution in the current study. It is verified that the optimal thrust vector is a function of the fundamental matrix of the given state equations. The cost function and the state vector during the reconfiguration can be analytically obtained as well. The results predict the form of optimal solutions in advance without having to solve the problem. Numerical simulation shows the brevity and the accuracy of the general analytic solutions developed in the current paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.71-76
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• 2008

This paper is concerned with the active vibration control of elevator by means of the active roller guide. To this end, a dynamic model for the horizontal vibration of the elevator consisting of a supporting frame, cage and active roller guides was derived using the energy method. Free vibration analysis was then carried out based on the equations of motion. Active vibration controller was designed based on the equations of motion using the LQR theory and applied to the numerical model. Rail irregularity and wind pressure variation were considered as external disturbance in the numerical simulations. The numerical results show that the active vibration control of elevator is possible.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.246-247
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• 2003

Large Eddy Simulation(LES) of turbulent spray combustion flow was conducted. An experimental database for the laboratory spray combustor is chosen to validate the present numerical simulation. The governing equations for the gas phases are discretized in three-dimensional curvilinear boundary-fitted coordinate system, and the fuel droplet motion equations are described in Lagrangian representation. The numerical results are compared with the experiment for the gas-phase mean velocities and its fluctuation in cold flow condition. Three dimensional vortical structures are well visualized and droplet motion is well predicted.