• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.389-394
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• 2014

This paper presents the effect of a reflective force computed from a first-order-hold method on the stability of a haptic system. A haptic system is composed of a haptic device with a mass and a damper, a virtual spring, a sampler and a sample-and-hold. The boundary condition of the maximum virtual stiffness is analytically derived by using the Routh-Hurwitz criterion and the condition shows that the maximum virtual stiffness is proportional to the square root of the mass and the damper of a haptic device and also is inversely proportional to the sampling time to the power of three over two. The effectiveness of the derived condition is evaluated by the simulation. When the reflective forces are computed by using the first-order-hold method, the maximum available stiffness to guarantee the stability is increased several hundred times as large as when the zero-order-hold method is applied.

• Structural Engineering and Mechanics
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• v.57 no.6
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• pp.989-1014
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• 2016

This paper deals with the analysis of the natural frequencies, mode shapes of an axially loaded beam system carrying ends consisting of non-concentrated tip masses and three spring-two mass sub-systems. The influence of system design and sub-system parameters on the combined system characteristics is the major part of this investigation. The effect of material properties, rotary inertia and shear deformation of the beam system is included. The end masses are elastically supported against rotation and translation at an offset point from the point of attachment. Sub-systems are attached to center of gravity eccentric points out of the beam span. The boundary conditions of the ordinary differential equation governing the lateral deflections and slope due to bending of the beam system including developed shear force frequency dependent terms, due to the sub.system suspension, have been formulated. Exact formulae for the modal frequencies and the modal shapes have been derived. Based on these formulae, detailed parametric studies are carried out. The geometrical and mechanical parameters of the system under study have been presented in non-dimensional analysis. The applied mathematical model is presented to cover wide range of mechanical, naval and structural engineering applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1733-1740
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• 2011

In this research, a MEMS vibratory gyroscope with dual-mass system in the sensing mode has been proposed to increase the stability of the device using wide bandwidth. A wide flat region between the two resonance peaks of the dual-mass system removes the need for a frequency matching typically required for single mass vibratory gyroscopes. Bandwidth, mass ratio, spring constant, and frequency response of the dual-mass system have been analyzed with MATLAB and ANSYS simulation. Designed first and second peaks of sensing mode are 5,917 and 8,210Hz, respectively. Driving mode resonance frequency of 7,180Hz was located in the flat region between the two resonance peaks of the sensing mode. The device is fabricated with anodically bonded silicon-on-glass substrate. The chip size is 6mm x 6mm and the thickness of the silicon device layer is $50{\mu}m$. Despite the driving mode resonance frequency decrease of 2.8kHz and frequency shift of 176Hz from the sensing mode due to fabrication imperfections, measured driving frequency was located within the bandwidth of sensing part, which validates the utilized dual-mass concept. Measured bandwidth was 768Hz. Sensitivity calculated with measured displacement of driving and sensing parts was 22.4aF/deg/sec. Measured slope of the sensing point was 0.008dB/Hz.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.3
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• pp.41-49
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• 1999

In this paper, we design a controller using the $\mu$-synthesis method and apply it for the spring-mass system with noncollocated sensors and actuators. We assume that the values of the spring stiffness and load mass of the plant are uncertain. The plant is modeled with parametric uncertainty by using the state space equation, especially the descriptor form. The $H_\infty$ controller designed by the $\mu$-synthesis method is compared with the standard $H_\infty$ controller To compare performances of two $H_\infty$ controllers, it is assumed that both controllers were designed with same weighting functions except that the $\mu$-synthesis controller has structured uncertainties. By compared with the standard $H_\infty$ controller, we show that the designed controller has satisfactory robust performance as well as robust stability by simulations and experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.483-491
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• 2005

In this paper a dynamic behavior of a double-cracked cantilever pipe with the tip mass and a moving mass is presented. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by using Lagrange's equation. The influences of the moving mass, the tip mass and double cracks have been studied on the dynamic behavior of a cantilever pipe system by numerical method. The cracks section are represented by the local flexibility matrix connecting two undamaged beam segments. Therefore, the cracks are modelled as a rotational spring. This matrix defines the relationship between the displacements and forces across the crack section and is derived by applying fundamental fracture mechanics theory. We investigated about the effect of the two cracks and a tip mass on the dynamic behavior of a cantilever pipe with a moving mass.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.71-78
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• 2000

Quickness and precision are the two most important requirements for an industrial scale used in production lines. In this paper, a new approach, "Mass-estimation algorithm by vibration-response measurement of dynamic balance", is presented to improve some of drawbacks in conventional scales. The system, consisted of velocity and displacement sensors, spring scale, analog-digital converter and microcomputer, is based on full utilization of dynamic mass measurement of velocity and displacement via microcomputer-assisted real time monitoring. The resulting system, when combined with appropriate mass estimation algorithm software, has shown its effectiveness in terms of two desirable characteristics required.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.361-365
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• 2002

This research is presented for optimizing the coefficients of spring and damper by impulse which is applied to AGV when the two containers are loaded on AGV. The suspension is estimated to the condition that two containers, initial velocity of container, initial height of container and maximum of suspension stroke. The coefficients of spring and damper are calculated numerically through Newmark method uses finite difference expansions. The procedure of calculation is applied by one DOFs of mass-spring-damper system. The coefficients of spring and damper have large value as increase of height or decrease of stroke. The result of calculation is shown in graph and the investigation is used AGV design.

• Journal of KSNVE
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• v.10 no.4
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• pp.575-583
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• 2000

In this paper, we design a vibration control system that includes a 3-D.O.F. mass-spring-damper structure for the analytical model of a building that is excited at the base of this structure by an external dynamic force, and one Active Mass Damper(AMD) on the top of this structure to generate control forces fro attenuation of the structural response. Two robust controllers based on $\mu$-synthesis and H$\infty$ optimal control are designed for the structural system to show that the performance of a control system can be degraded by some parameter uncertainties such as mass, stiffness coefficients, and/or damping coefficients. The performance of the two controllers are compared in terms of nominal performance, robust stability and robust performance by simulations.

• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.505-511
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• 2018

Recently, a new foundation model called "Dynamic foundation model" was proposed for the dynamic analysis of structures on the foundation. This model includes a linear elastic spring, shear layer, viscous damping and the special effects of mass density parameter of foundation during vibration. However, the relationship of foundation property parameters with the experimental parameter of the influence of foundation mass also has not been established in previous research. Hence, the purpose of the paper presents a simple experimental model in order to establish relationships between foundation properties such as stiffness, depth of foundation and experimental parameter of the influence of foundation mass. The simple experimental model is described by a steel plate connected with solid rubber layer as a single degree of freedom system including an elastic spring connected with lumped mass. Based on natural circular frequencies of the experimental models determined from FFT analysis plots of the time history of acceleration data, the experimental parameter of the influence of foundation mass is obtained and the above relationships are also discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.743-744
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• 2014

Hyperbolic metamaterials in which waves can only propagate through the radial direction have achieved much attention these days due to their capability of sub-wavelength resolution. In this work, the realization and optimization of hyperbolic elastic metamaterials are mainly studied. To obtain a new hyperbolic elastic metamaterial, a specially-engineered mass-spring system is introduced. Based on the mass-spring system, the hyperbolic elastic metamaterials are proposed and realized. In addition, the sub-wavelength resolution of the proposed hyperbolic elastic metamaterial is verified by ultrasonic elastic wave experiments. For the experiments, specially-designed magnetostrictive patch transducers are developed to realize two sub-wavelength elastic wave sources. Furthermore, the proposed hyperbolic elastic metamaterial is optimized to maximize its operating frequency ranges by the topology optimization method.