• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.153-159
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• 1997

This paper presents the swing motion analysis of the container crane headblock with the passive control device using hydraulic motors and anti-swing ropes. The device hauls at the headblock to opposite direction of its swing motion using the tension difference between anti-swing ropes connected to the headblock. To consider this control mechanism, the headblock is modelled as the rigid bar suspended by two hoist ropes at the overhead trolley and its non-linear equation of motion is derived using Lagrange's equation. Some numerical experiments using the equation are carried out to investigate the swing motion characteristics of the headblock under the variation of geometric relation among the cargo handling components and to evaluate the performance of the anti-swing device.

• Computers and Concrete
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• v.9 no.3
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• pp.195-213
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• 2012

This paper presents the investigation of the stochastic responses of seismically isolated bridges subjected to spatially varying earthquake ground motions including incoherence, wave-passage and site-response effects. The incoherence effect is examined by considering Harichandran and Vanmarcke coherency model. The effect of the wave-passage is dealt with various wave velocities in the response analysis. Homogeneous firm, medium and soft soil conditions are selected for considering the site-response effect where the bridge supports are constructed. The ground motion is described by filtered white noise and applied to each support points. For seismic isolation of the bridge, single and double concave friction pendulum bearings are used. Due to presence of friction on the concave surfaces of the isolation systems, the equation of motion of is non-linear. The non-linear equation of motion is solved by using equivalent linearization technique of non-linear stochastic analyses. Solutions obtained from the stochastic analyses of non-isolated and isolated bridges to spatially varying earthquake ground motions compared with each other for the special cases of the ground motion model. It is concluded that friction pendulum systems having single and double concave surfaces have important effects on the stochastic responses of bridges to spatially varying earthquake ground motions.

• Journal of the Korean Statistical Society
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• v.34 no.3
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• pp.197-208
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• 2005

We consider the problem for approximate solution of linear stochastic evolution equations driven by infinite-dimensional fractional Brownian motion with Hurst parameter $H\;\in$ (0,1/2). The error of the approximate solution for the explicit Euler scheme is investigated.

• Journal of the Korean Institute of Navigation
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• v.10 no.1
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• pp.129-138
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• 1986

A matrix partitioning method is proposed for the 2-D motion analysis of floating bodies. For the numerical solution, the boundary of a floating body is approximated with a series of line segments and the governing integral equation is transformed into a system of linear equations. A new solution procedure of resulting linear equation with complex coefficients is formulated and programmed using a matrix partitioning scheme and the Choleski decomposition. From the case study, it is found that the proposed method is efficient in the motion analysis of floating bodies, especially in the calculation of hydrodynamic coefficients. Also, it requires smaller memory size and less computing time compared with conventional methods.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.9 s.90
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• pp.868-876
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• 2004

The linear motion(LM) guide using ball bearing has many advantages compared with conventional sliding guides. Therefore, LM guide using ball bearing has been widely used to increase the accuracy of the position of a system. This research investigates dynamic characteristics of LM guide through mainly linear analyses. Linear analysis is accomplished by Lagrange equation and the finite element method. And another trial that performs nonlinear analysis about one mode(bouncing mode) of LM guide from Hertzian contact theory is accomplished in the latter half of this research. Through nonlinear analysis we could observe the softening characteristic due to the Hertzian contact nonlinearity.

• Journal of Korean Association for Spatial Structures
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• v.24 no.1
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• pp.65-72
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• 2024

This paper aims to advance our understanding of extensible beams with multiple cracks by presenting a crack energy and motion equation, and mathematically justifying the energy functions of axial and bending deformations caused by cracks. Utilizing an extended form of Hamilton's principle, we derive a normalized governing equation for the motion of the extensible beam, taking into account crack energy. To achieve a closed-form solution of the beam equation, we employ a simple approach that incorporates the crack's patching condition into the eigenvalue problem associated with the linear part of the governing equation. This methodology not only yields a valuable eigenmode function but also significantly enhances our understanding of the dynamics of cracked extensible beams. Furthermore, we derive a governing equation that is an ordinary differential equation concerning time, based on orthogonal eigenmodes. This research lays the foundation for further studies, including experimental validations, applications, and the study of damage estimation and detection in the presence of cracks.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.955-963
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• 2005

This research investigates dynamic characteristics of a linear motion (LM) guide through a experimental result and theoretical analysis. The stiffness in the LM guide is determined by the preloading due to the minus clearance between the ball bearing and the contact surface and it can be derived by Hertzian contact theory and the nonlinear motion of equation. The vibration analysis is performed using Lagrange equations and its result agrees with the experiment result. Using the sensitivity analysis on design parameters such as the contact angles of ball bearings and the eccentricity of mass center, the variation of the natural frequencies can be predicted.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.170-171
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• 2022

A ship's maneuvering motion model is important in a computer simulation, especially under the trend of intelligent navigation. This model is usually constructed by the hydrodynamic parameters of the ship which are generated by the principles of hydrodynamics. Ship's motion model is a nonlinear function. By using this function, ships' motion elements can be calculated, then the ship's trajectory can be predicted. Deeping neural networks can construct any linear or non-linear equation theoretically if there have enough and sufficient training data. This study constructs some kinds of deep Networks and trains this network by real ship motion data, and chooses the best one of the networks, uses real data to train it, then uses it to predict the ship's trajectory, getting some conclusions and experiences.

• Proceedings of the KIEE Conference
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• 2000.11d
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• pp.765-768
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• 2000

Linearization of the biped dynamic equations and design of linear controller for the linearized equations are studied in this paper. The biped robot with inverted pendulum type trunk, used to stabilize the dynamic balancing of the biped robot during dynamic walking period, is modelled with 14 DOF and simulated. Despite of well defined linear control theories so far, the linear control methods was limited to the applications for a walking robot, because they have been inherently strong nonlinear properties, such as a modeling parameter uncertainties, external forces as noise, inertial and Coriolis terms by three dimensional modeling and so on. To linearize the nonlinear equations of motion of biped robot on MIMO and time varying linear equations of motion, 1st order Taylor series is used to formulate the linear equation. And a 2nd order numerical perturbation method Is used to approximate partial differential equations. Using the linearized equations of motion, a linear controller is designed by pole placement method with feed forward compensation. Using the obtained linearized equations and linear controller, the continuous walking simulation is performed.

• Structural Engineering and Mechanics
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• v.34 no.4
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• pp.507-523
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• 2010

Parametric and forced non-linear vibrations of an axially moving rotor both in non-resonance and near-resonance cases have been investigated analytically in this paper. The axial speed is assumed to involve a mean value along with small harmonic fluctuations. Hamilton's principle is employed for this gyroscopic system to derive three coupled non-linear equations of motion. Longitudinal inertia is neglected under the quasi-static stretch assumption and two integro-partial-differential equations are obtained. With introducing a complex variable, the equations of motion is presented in the form of a single, complex equation. The method of multiple scales is applied directly to the resulting equation and the approximate closed-form solution is obtained. Stability boundaries for the steady-state response are formulated and the frequency-response curves are drawn. A number of case studies are considered and the numerical simulations are presented to highlight the effects of system parameters on the linear and nonlinear natural frequencies, mode shapes, limit cycles and the frequency-response curves of the system.