• 한국산학기술학회논문지
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• 제19권11호
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• pp.561-567
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• 2018

본 연구는 동력분산형 고속열차의 승차감을 개선하기 위하여 진행되었다. 동력분산형 고속열차 시제차량의 동역학 해석을 통해 300km/h이상의 임계속도를 갖는 등가 답면구배의 범위는 0.05에서 0.25사이임을 확인하였다. 초기에 적용된 차륜 프로파일 S1002는 4만km이상의 누적주행거리에도 불구하고 등가 답면구배는 0.033 정도였고, 안정적인 운행을 위해서는 등가 답면구배가 0.061이 넘는 XP55가 더 적합함을 확인하였다. 동력분산형 고속열차의 승차감을 개선하기 위한 방안으로 요댐퍼의 설치 각도를 $7.35^{\circ}$에서 $0^{\circ}$로 변경하고, 민감도 분석과 최적화를 통해 도출된 공기스프링 횡 및 상하방향 강성 30% 감소, 2차 수직댐퍼 및 횡댐퍼 댐핑계수를 50% 증가시키는 방안을 제안하였다. 이를 적용하면 차체 가속도를 평균 20%정도 개선시킬 수 있을 것으로 예상되었다. 도출된 승차감 개선 방법의 일부인 요댐퍼 설치각도를 $0^{\circ}$로 변경하고 횡댐퍼의 댐핑계수를 30% 증가시킨 후 경부고속선에서 300km/h 속도로 시운전을 진행하였을 때, 차체 횡가속도는 평균 34.3% 개선되었고, 본 연구에서 제안된 추가적인 개선 방안은 향후 시운전 시험 시에 적용될 예정이다. 본 연구에서 사용된 승차감 개선 프로세스는 향후 동력분산형 고속열차의 상업 운행 시에 발생할 수 있는 승차감 관련 문제 해결에 사용될 수 있다.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.12-18
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• 2021

본 연구는 강제진동으로 인해 교량에 발생되는 휨 변위를 효과적으로 완화하는 것이 목적이다. 단순보의 휨거동 제어를 위하여 스프링과 mass의 관계를 결합한 CTMD(Combine Tuned Mass Damper)를 개발하였다. 개발한 CTMD는 교량의 특성에 따라 질량비의 조절이 가능하도록 CTMD 내부의 Mass를 가감할 수 있는 Mass slot과 Mass block을 설계 제작하였다. CTMD에 적용된 Spring의 최대하중은 33.15N으로 고정하였다. 개발된 CTMD의 성능을 평가하기 위하여 길이 10m, 폭 0.6m, 높이 0.74m인 단순보를 제작하였다. 단순보의 지점조건은 한단 힌지, 한단 롤러로 구성하였다. 실험 방법은 단순보의 중앙에 CTMD를 설치하고 Mass를 조절하여 질량비에 변화를 주어 실험하였다. 이때 질량비에 따른 휨 거동 제어효과는 단순보의 중앙에 설치한 LVDT를 이용하여 측정하였다. 가진 조건은 단순보의 최대 휨 거동을 유발시키기 위하여 단순보의 힌지단에서 1.25m 떨어진 곳에 관성형가진기를 설치하여 3Hz로 흔들었다. 실험 결과 최적의 질량비가 2.1일 때 휨 거동 변위의 감쇠율이 약 71.2%로 최상의 제어효과를 나타내는 것으로 확인되었다.

• 동력기계공학회지
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• 제12권2호
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• pp.23-28
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• 2008

The primary objective of this study is to truly understand reaction force be due to engine exciting force. Exciting forces of the engine apply a source of the vehicle NVH(Noise, Vibration, Harshness). To understand reaction force was applied MSC.Nastran software. Analyzed frequency response analysis of powertrain mount system. First, engine exciting force was applied field function. Also nonlinear characteristics was applied field function : such as dynamic spring constant and loss factor. And nonlinear characteristics was applied CBUSH. Generally characteristics of rubber mount is constant frequency. But characteristics of hydraulic mount depend to frequency. Therefore nonlinear characteristics was applied. Powertrain mounting system be influenced by powertrain specification, mount position, mount angle and mount characteristics etc. In this study, we was analyzed effects of powertrain mounting system. And we was varied dynamics spring constant and loss factor of mounts.

• 한국해양공학회지
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• 제26권1호
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• pp.70-77
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• 2012

In this study, a numerical analysis of offshore installation using a floating crane with heave compensator is carried out in time domain. The motion analysis of crane vessels is based on floating body dynamics using convolution integral and the crane wire is treated as simple spring. The lifted structure is assumed as a rigid body with 3 degree-of-freedom translational motion. The heave compensator is numerically modelled by the generalized spring-damper system. Firstly, forced motion simulations of crane wire system are carried out to figure out the basic principle of heave compensator. The transfer function of crane wire system is obtained and effective wave period of heave compensator are found. Then, coupled analysis of crane vessel, crane wire, and lifted structure are performed in regular and irregular sea conditions. Two different crane vessels and two lifted structures (suction pile and manifold) are considered in this study. Through a series of numerical calculations, the effective zone of heave compensator is investigated with respect to wave period and crane wire length.

• 한국해양공학회지
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• 제23권5호
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• pp.15-24
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• 2009

The results of a simulation study of variable liquid column oscillations in U-tanks with a novel control scheme are presented. The configuration under investigation is analogous to that of the tuned liquid-column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. However, by virtue of an adequate controller, the response of amplitude of the U-tanks becomes larger in a desired frequency range. The motion of wave energy conversion system equipped with a variable liquid column oscillator is described by a series of nonlinear differential equations. The equations describe the motion of body under ocean wave excitation, and the motion of liquid with an air-spring effect caused by the compression and expansion of air in vertical liquid columns and air chambers. It is shown that the effect of the air-spring has a vital role to maintain the natural frequency of oscillation in the system to synchronize with the frequency of the ocean wave, thus the system provides the most effective mode for energy extraction from the ocean.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2004년도 춘계학술대회 논문집
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• pp.131-135
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• 2004

강착장치에 의한 지면반력은 착륙과 이륙시 지면과의 상호작용을 나타내며 고도를 감지하여 지면에 접촉하였을 때 지면의 반력을 헬리콥터에 전달해주는 역할을 한다. 비행시뮬레이션에 있어서 강착장치는 비행 중 비행특성에 미치는 영향이 없기 때문에 비행특성 분석용 또는 비행제어용 비행시뮬레이션 프로그램에서는 강착장치를 생략하여 시뮬레이션 하는 경우가 많다. 하지만 훈련의 목적으로 사용하는 경우 착륙과 이륙은 큰 비중을 차지하며 무인기의 함상 착륙과 같은 시뮬레이션에서는 필수적인 요소로 대두되고 있다. 본 논문에서 강착장치는 1자유도의 mass, spring, damper의 간단한 진동시스템을 택하였고, 강착장치의 접촉점인 지면은 고도 0인 평탄한 지면으로 가정하였다. 추후 지면을 6자유도를 가지는 움직이는 평면으로 쉽게 대체할 수 있도록 벡터형식으로 된 모델을 선택하였다.

• 한국소음진동공학회논문집
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• 제17권10호
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• pp.958-966
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• 2007

This study presents full vehicle dynamics model for the dynamic characteristic analysis of chassis parts which are suspension and brake system. This vehicle dynamics model is appled to kinematics and quasi-static analysis for each chassis part. In order to develop the vehicle dynamics model, the parameters of each chassis element part which are bush, spring and damper are measured by experiment. Also the wheel forces and moments of 6 DOF are measured at each wheel center. These data are applied to input parameter for vehicle dynamics model. And the verification of the developed model is achieved to comparison with the experimental force data of spring, trailing arm and assist arm by using the load response by strain gauge. These experimental force data are acquired by road test at event surfaces of P/G which are belgian and chuck holes roads.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권2호
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• pp.74-80
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• 2000

In this paper, we present a control method of mobile power assist systems. Most of mobile power assist systems have a heavy base for preventing easy tumbling, so continual movement of the base during operations causes high energy consumption and gives the high risk of human injury. Furthermore, the slow dynamics of the base limits the frequency bandwidth of the whole system. Thus we propose a cooperation control method of the mobile base and manipulator, which removes the unnecessary movements of the base. In our scheme, the mobile base does not move until the center of gravity(C.G) of the system goes outside a safety region. When C.G. reaches the boundary of the safety region, the base starts moving to recover the manipulator's initial configuration. By varying the parameters of a human impedance controller, the operator is warned by a force feedback that C.G. is on the marginal safety region. Our scheme is implemented by assigning a nonlinear mass-damper-spring impedance to the tip of the manipulator. Our scheme is implemented by a nonlinear mass-spring impedance to the tip of the manipulator. The experimental results show the efficacy of the proposed control method.

• Smart Structures and Systems
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• 제20권6호
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• pp.739-757
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• 2017

The main goal of this study is to investigate the hysteretic behavior of polyurethane rubber springs in compression with and without precompression. The precompression is introduced to provide rigid force in the behavior, and thereby a precompressed rubber spring can be used for a restoring element. For the goal, this study prepares nine rubber springs for three suites which are all cylindrical in shape with a hole at the center. The rubber springs in each suite have different dimensions of diameter and length but have similar shape factors; thus, they are designed to have a similar compressive stiffness. Three rubber springs from the nine are tested with increasing compressive strain up to 30% strain to investigate the behavior of the rubber springs without precompression as well as the effect of the loading strain. The nine springs are compressed up to 30% strain with increasing precompressive strain from 0 to 20% at increments of 5%. The study analyzes the effective stiffness and damping ratio of the rubber springs with and without precompression, and the rigid force of the precompressed rubber springs is discussed. Finally, this study suggests a regression method to determine the minimum required precompression to eliminate residual strain after unloading.

• Smart Structures and Systems
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• 제32권6호
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• pp.383-391
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• 2023

Energy harvesting in trams may become a prevalent source of passive energy generation due to the high density of vibrational energy, and this may help power structural health monitoring systems for the trams. This paper presents a broadband vibrational energy harvesting device design that utilizes a varied frequency from a tram vehicle using a 2 DOF vibrational system combined with electromagnetic energy conversion. This paper will demonstrate stepwise optimization processes to determine mechanical parameters for frequency tuning to adjust to the trams' operational conditions, and electromagnetic parameters for the whole system design to maximize power output. The initial optimization will determine 5 important design parameters in a 2 DOF vibrational system, namely the masses (m₁, m₂ (and spring constants (k₁, k₂, k₃). The second step will use these parameters as initial guesses for the second optimization which will maintain the ratios of these parameters and present electrical parameters to maximize the power output from this system. The obtained values indicated a successful demonstration of design optimization as the average power generated increased from 1.475 mW to 17.44 mW (around 12 times).