• 한국기계가공학회지
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• 제10권1호
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• pp.87-92
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• 2011

This article proposes a new technique of the dynamic model using multi-body dynamic analysis tool for a flexible main spindle rotor system with a novel phase adjusting control technique for the purpose of an active control of rotor vibration. The dynamic model is used as a plant model. Also in order to make control system, a component parameters and phase controller is composed and simulated by SIMULINK. The vibration is reduced to 50%. Therefore the ADAMS dynamic model for the flexible main spindle rotor and the phase adjusting control techniques may be effective for the suppressing the vibration and helpful for the future active control for rotor vibration.

• Wind and Structures
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• 제15권6호
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• pp.495-508
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• 2012

The present paper is focused on the prediction of the acrosswind aeroelastic response of square tall buildings. In particular, a semi-analytical procedure is proposed based on the assumption that square tall buildings, for reduced velocities corresponding to operational conditions, do not experience vortex shedding resonance or galloping and fall in the range of positive aerodynamic damping. Under these conditions, aeroelastic wind tunnel tests can be unnecessary and the response can be correctly evaluated using wind tunnel tests on rigid models and analytical modeling of the aerodynamic damping. The proposed procedure consists of two phases. First, simultaneous measurements of the pressure time histories are carried out in the wind tunnel on rigid models, in order to obtain the aerodynamic forces. Then, aeroelastic forces are analytically evaluated and the structural response is computed through direct integration of the equations of motion considering the contribution of both the aerodynamic and aeroelastic forces. The procedure, which gives a conservative estimate of the aeroelastic response, has the advantage that aeroelastic tests are avoided, at least in the preliminary design phase.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권3호
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• pp.93-100
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• 2003

Switched reluctance motor(SRM) has some advantages such as low cost, high torque density but SRM has essentially high torque ripple due to its salient structure. In order to apply SRM to industrial field, torque ripple has to be reduced. This paper introduces optimal design process of SRM using an optimization algorithm of Progressive Quadratic Response Surface Modeling(PQRSM) and two-dimensional(2D) Finite Element Method(FEM). The electrical and geometrical design parameters have been adopted as 2D design variables. From this work, it can be obtained both the optimal design minimized torque ripple and the optima1 design maximized the average torque, respectively. Finally, this Paper Presents Performance comparison of two optimal designs and consider influence of the selected design variables in torque characteristics.

• 대한기계학회논문집A
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• 제21권5호
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• pp.756-768
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• 1997

In order to control a dynamic gait of quadrupedal walking robot, the equations of motion of the whole mechanism are required. In this research, the equations of motion are formulated analytically using Kane's dynamic approach. As a dynamic gait model, a trot gait has been adopted. The degree of freedom of whole mechanism could be reduced to 7 by idealizing the kinematic feature of the trot gait. Using the equations of motion formulated, the results of the redundant-joint torque analysis and the simulation of dynamic walking motion are presented.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.435-440
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• 2001

In this study, torsional and lateral vibrations of a gear box transmission system were analyzed theoretically using some mathematical models and examined to determine the causes of its excessive vibrations. As the results, it was found there exist possibility of resonance between gear mesh frequencies and lateral vibration mode of the transmission shaft during the third shifting mode operation. In order to avoid this resonance, we proposed changing the arrangement of gears on the transmission shaft. The measured vibration levels of the improved gear box were dramatically reduced. These results may be helpful to design a machine tool gear box with low noise and vibration.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1063-1068
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• 2008

A lens system of a camera module for mobile phones is comprised of the composition and design of various shapes of lens. To improve responses such as the modular transfer function (MTF), a lens system should always be constructed by considering uncertainty that can be caused by manufacturing and assembly error. In this study, tolerance optimization using the Latin Hypercube Sampling (LHS) technique is performed. In order to reduce the computational burden of the tolerance optimization process and decrease the influence from numerical noise effectively, we use the Progressive Quadratic Response Surface Modeling (PQRSM), which is one of Sequential Approximate Optimization (SAO) techniques. Using this method, we achieved optimal tolerance for each lens and obtained reliability for satisfying user‘s requirements. In addition, through the design process the manufacturing and assembly cost of a lens system was reduced.

• Journal of Communications and Networks
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• 제5권3호
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• pp.230-239
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• 2003

In this paper, we propose a framework to study how to route packets efficiently in multipath communication networks. Two traffic congestion control techniques, namely, flow assignment and packet scheduling, have been investigated. The flow assignment mechanism defines an optimal splitting of data traffic on multiple disjoint paths. The resequencing delay and the usage of the resequencing buffer can be reduced significantly by properly scheduling the sending order of all packets, say, according to their expected arrival times at the destination. To illustrate our model, and without loss of generality, Gaussian distributed end-to-end path delays are used. Our analytical results show that the techniques are very effective in reducing the average end-to-end path delay, the average packet resequencing delay, and the average resequencing buffer occupancy for various path configurations. These promising results can form a basis for designing future adaptive multipath protocols.

• 한국지진공학회논문집
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• 제20권2호
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• pp.79-89
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• 2016

If scour is occurred at shallow foundation of bridge, seismic performance of the bridge will be reduced. In order to evaluate accurate seismic response of bridge according to scour depths, modeling of foundation reflecting scour effect is important. In this study, taking into account the effect of the reduction in embedment depth of the shallow foundation by scouring, the soil around the foundation is modelled as an equivalent soil spring with various stiffness. Seismic fragility analyses for 3 types of bridges subjected to 4 types of ground motions classified into Site Class A, B, C, D are evaluated according to several scour depths. From the fragility analysis results, it can be observed that the deeper the scour depth, the higher probability of exceeding damage states. Also, seismic failure probability of asymmetric bridge is higher than that of symmetric bridge.

• 제어로봇시스템학회논문지
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• 제3권3호
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• pp.214-218
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• 1997

We propose a VSC(Variable Structure Controller) with a PI-type reaching law. In General, conventional VSCs with a reaching law including a discontinuous term have the chattering problem, and thus the system may be unstable due to the disregarded high frequency dynamics in the modeling process. To resolve this problem, the PI-type reaching law is proposed in this paper. The proposed reaching law makes it easy to determine the reaching dynamics as well as the reaching time by utilizing the 2nd-order system analysis. Furthermore, since the discontinous term is not involved in the reaching law, the chattering is considerably reduced. To show the effectiveness of the proposed scheme, the stability of the proposed system is proved by Lyapunov method and the computer simulations are performed for the Ball Balance System.

• 유공압시스템학회논문집
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• 제5권3호
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• pp.1-8
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• 2008

The optimal design of a large-size fully hydraulic breaker is studied in this paper. Mathematical modeling of the breaker is established and verified by experiments. Through sensitivity analysis, the key design parameters of the breaker are selected, which mostly affect the performance of the breaker. Taguchi method is used to optimize the key design parameters in order to maximize the output power through simulation using AMESim. As a result, the impact energy is increased by 18.9% and the output power is increased by 12.4% compared with the current design. The pressure pulsation in the supply line is also reduced by the optimization.