• The Journal of Korea Robotics Society
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• v.1 no.2
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• pp.135-141
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• 2006

This paper presents offline estimation of equivalent physical damping parameter in haptic interaction systems where damping is the most important parameter for stability. Based on the previous energy bounding algorithm, an offline procedure is developed in order to estimate the physical damping parameter of a haptic device by measuring energy flow-in to the haptic device. The proposed method does not use force/torque sensor at the handgrip. Numerical simulation and experiments verified effectiveness of the proposed method.

• Advances in nano research
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• v.13 no.2
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• pp.147-164
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• 2022

This article investigates the longitudinal vibration of a nanorod embedded in viscoelastic medium according to the nonlocal strain gradient theory. Viscoelastic medium is considered based on Kelvin-Voigt model. Governing partial differential equation is derived based on longitudinal equilibrium and analytical solution is obtained by adopting harmonic motion solution for the nanorod. Modal frequencies and corresponding damping ratios are presented to demonstrate the influences of nonlocal parameter, material length scale, elastic and damping parameters of the viscoelastic medium. It is observed that material length scale parameter is very influential on modal frequencies especially at lower values of nonlocal parameter whereas increase in length scale parameter has less effect at higher values of nonlocal parameter when the medium is purely elastic. Elastic stiffness and damping coefficient of the medium have considerable impacts on modal frequencies and damping ratios, and the highest impact of these parameters on frequency and damping ratio is seen in the first mode. Results calculated based on strain gradient theory are quite different from those calculated based on classical elasticity theory. Hence, nonlocal strain gradient theory including length scale parameter can be used to get more accurate estimations of frequency response of nanorods embedded in viscoelastic medium.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1459-1464
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• 1996

The most important parameter for hydraulic active suspension system is to sustain desirable vehicle maneuvering stability and ride comfort without increasing consumption power. The performance of hydraulic active suspension system depends on damping force of body damping valve and piston damping valve. Hydraulic actuator design and damping valve parameter selection are essential and basic procedure to design hydraulic active suspension system. This paper is on computer simulation with use of mathematical model that was delivered from dynamic characteristic of hydraulic actuator, as know basic damping characteristics of hydraulic active suspension system. The aim of this paper is to select the system parameter that affect mainly hydraulic active suspension, and identify the validity on the system parameter selection.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.683-692
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• 2002

The most important parameter for hydraulic active suspension system is to sustain desirable vehicle maneuvering stability and ride comfort without increasing power consumption. The performance of hydraulic active suspension system depends on damping force of body damping valve and piston damping valve. Hydraulic actuator design and damping valve parameter selection are essential and basic procedure to design hydraulic system. This paper is on computer simulation with use of mathematical model that was delivered from dynamic characteristic of hydraulic actuator, as know basic damping characteristics of hydraulic active suspension system. The aim of this paper is to select the system parameter that affect mainly hydraulic active suspension, and identify the validity on the system parameter selection.

• Journal of the Korea Society of Computer and Information
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• v.15 no.4
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• pp.57-63
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• 2010

The damping parameter of Levenberg-Marquardt algorithm switches between error backpropagation and Gauss-Newton learning and affects learning speed. Fixing the damping parameter induces some oscillation of error and decreases learning speed. Therefore, we propose the way of a variable damping parameter with referring to the alternation of error. The proposed method makes the damping parameter increase if error rate is large and makes it decrease if error rate is small. This method so plays the role of momentum that it can improve learning speed. We tested both iris recognition and wine recognition for this paper. We found out that this method improved learning speed in 67% cases on iris recognition and in 78% cases on wine recognition. It was also showed that the oscillation of error by the proposed way was less than those of other algorithms.

• International Journal of Automotive Technology
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• v.5 no.3
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• pp.189-194
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• 2004

The viscoelastic layer material is widely used to control the noise and vibration characteristics of the panel structure. This paper describes the design technology of the effective vibration damping treatment using the concept of the equivalent parameter of viscoelastic layer materials. Applying the equivalent parameter concepts based on theories of shell, it is possible to simulate the finite element analysis of damping layer panel treatments on the vibration characteristics of the structure. And it is achieved the reduced computational cost and the optimal design of topological distribution for the reduction of vibration effect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.48-55
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• 2018

The purpose of the present study is to compare the reduction rate of natural frequency and the increase rate of damping parameter with structural damage in system. For this purpose, experiment and numerical simulation analysis are performed for the 2-span H-Beam with lower natural frequency and higher damping parameter from free vibration in structure. The response signal by impact load before and after damage is analyzed at 14 locations. The response signals for all locations are performed fast fourier transform to estimate the natural frequency reduction rate and wavelet transform to estimate the damping parameter increase rate. The time domain function corresponding to each scale(frequency) is separated from the response signal by wavelet parameter. The estimation of damping parameter increase rate using wavelet transform is more sensitive than the estimation of natural frequency reduction rate in structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.30-37
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• 2015

The estimation of system damping parameter of the response signal with lower natural frequency and higher damping parameter from free vibration is affected by the wavelet center frequency. This study discusses these considerations in the context of the wavelet's multi-resolution character and includes guidelines for selection of wavelet center frequency. The experiment with H-Beam and numerical examples with respect to three cases (i)single mode, (ii)separated modes and (iii)close modes demonstrate the validity of method to improve the accuracy of the estimated damping parameter. The localization of the corresponding scale for the total scales is determined by the natural frequency of the analysing mode and is affected by the wavelet center frequency. Thus, the reliability for the accuracy of the estimated damping parameter can be improved by the corresponding scale of the natural frequency for the analysing mode is localized at the half of the total scales.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.150-150
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• 2000

We as modal parameter estimation technique by developing a residual based system reconstruction and using the system matrix coordinate transformation. The modal parameters can be estimated from and residues of the system transfer functions expressed in modal coordinate basis, derived from the state space system matrices. However, for modal parameter estimation of multivariable and order structural systems over broad frequency bands, this non-iterative algorithm gives high accuracy in the natural fre- and damping ratios. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios on be estimated using tile coordinates of the structural system reconstructed fro the experimental frequency response. These results are compared with those of finite element analysis and single-degree-of-freedom curve-fitting.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.527-527
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• 2000

Wean modal parameter estiimation technique by developing a residual based system reconstruction and using the system matrix coordinate transformation. The modal parameters can be estimated from and residues of the system transfer functions expressed in modal coordinate basis, derived from the state space system matrices. However, for modal parameter estimation of mllltivariable and order structural systems over broad frequency bands, this non-iterative algorithm gives high accuracy in the natural fre and damping ratios. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios can be estimated using the coordinates of the structural system reconstructed from the experimental frequency response. These results are compared with those of finite element analysis and single-degree-of-freedom curve-fitting..