• 로봇학회논문지
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• 제12권3호
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• pp.356-364
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• 2017

This paper presents a force control based on the observer without taking any force or torque measurement from the robot which allows realizing more stable and robust human robot interaction for the developed multi-functional upper limb rehabilitation robot. The robot has four functional training modes which can be classified by the human robot interaction types: passive, active, assistive, and resistive mode. The proposed observer consists of internal disturbance observer and external force observer for distinctive performance evaluation. Since four training modes can be quantitatively identified as impedance variation, position-based impedance control with feedback and feedforward controller was applied to the assistive training mode. The results showed that the proposed sensorless observer estimated cleaner and more accurate force compared to the force sensor and the impedance controller embedded with the proposed observer completed the assistive training mode safely and properly.

• 한국산업융합학회 논문집
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• 제3권1호
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• pp.43-51
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• 2000

The response statistics of a hinged-clamped beam under broad-band random excitation is investigated. The random excitation is applied at the nodal point of the second mode. By using Galerkin's method the governing equation is reduced to a system of nonautonomous nonlinear ordinary differential equations. A method based upon the Markov vector approach is used to generate a general first-order differential equation in the dynamic moment of response coordinates. By means of the Gaussian and non-Gaussian closure methods the dynamic moment equations for the random responses of the system are reduced to a system of autonomous ordinary differential equations. The case of two mode interaction is considered in order to compare it with the case of three mode interaction. The analytical results for two and three mode interactions are also compared with results obtained by Monte Carlo simulation.

• Journal of Mechanical Science and Technology
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• 제14권6호
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• pp.633-644
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• 2000

Recently, in proportion to the increase of earthquake occurrence-frequency and its strength in the countries within the circum-pan Pacific earthquake belt, a concept of earthquake-proof design for huge structures containing liquid has been growing up. This study deals with the refinement of classical numerical approaches for the free vibration analysis of separated structure and liquid motions. According to the liquid-structure interaction, LNG-storage tanks exhibit two distinguished eigenmodes, the sloshing mode and the bulging mode. For the sloshing -mode analysis, we refine the classical rigid-tank model by reflecting the container flexibility. While, for the bulging-mode analysis, we refine the classical uncoupled structural vibration system by taking the liquid free-surface fluctuation into consideration. We first construct the refined dynamic models for both problems, and present the refined numerical procedures. Furthermore, in order for the efficient treatment of large-scale matrices, we employ the Lanczos iteration scheme and the frontal-solver for our test FEM program. With the developed program we carry out numerical experiments illustrating the theoretical results.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2541-2549
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• 2002

In order to study the vibration characteristics of fluid-structure interaction problem, two rectangular plates coupled with bounded fluid were investigated. Experimental modal analyses were carried out to extract the modal parameters of the system. Additionally. finite element modal analyses performed using a commercial computer code, ANSYS. The FEM solutions were compared with the experimental solutions to verify the finite element model. As a result, the comparison between the experiment and FEM results showed excellent agreement. The transverse vibration modes, in-phase and out-of-phase, were observed alternately in the fluid-coupled system. The thickness effect of the plates on the fluid-coupled natural frequencies and mode shapes was investigated for two different cases with the identical thickness and the unequal thickness. It was found that the coupled natural frequencies increase with the thickness for the identical plates regardless of the mode phase. The experimental and the finite element analysis results showed that the out-of-phase mode shapes were deviated from the symmetrical mode shapes in the plate transverse direction fur the unequal plate thickness case.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.163-177
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• 2021

Numerical simulations of the Vortex-Induced Vibration (VIV) about a large-scale flexible pipe subject to shear flow were carried out in this paper. Efficiency verification was performed firstly, validating that the proposed fluid-structure interaction solution strategy is competent in predicting the VIV response. Then, the VIV characteristics related to multi-mode and spanwise hybrid waveform about the flexible pipe attributed to shear flow were investigated. When inflow velocity rises, higher vibration modes are apt to be excited, and the spanwise waveform easily convertes from a standing-wave-dominated status to a hybrid standing-traveling wave status. The multi-mode or even multiple-dominant-mode is prone to occur, that is, the dominant mode is often followed by several apparent subordinate modes with considerable vibration energy. Hence, the shedding frequencies no longer obey Strouhal law, and vibration trajectories become intricate. According to the motion analysis concerning the coupled cross-flow and in-line vibrations, as well as the corresponding wake patterns, a tight coupling interaction exists between the structural deformation and the wake flow behind the flexible pipe. In addition, the evolution of the vortex tube along the pipe span and a strong 3D effect are observed due to the slenderness of the flexible pipe and the variability of the vortex shedding attributed to the shear flow.

• 한국HCI학회논문지
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• 제12권1호
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• pp.15-23
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• 2017

이 연구는 인간성의 개념과 구성 요인들을 스마트 홈 맥락에서 대화형 에이전트에 적용하여, 의인화의 수준과 인터랙션 유형이 사용자 감성 경험과 향후 이용 의도에 미치는 효과를 알아보고자 하였다. 실험연구를 통한 분석 결과 의인화의 고-저 수준과 인터랙션의 음성-채팅 유형은 친밀도, 호감도, 향후 이용 의도에 영향을 미치는 것으로 나타났다. 즉, 의인화 수준이 높고, 음성 인터랙션인 경우 대화형 에이전트를 더 친밀하고 호감이 가며 향후에도 계속해서 이용하고 싶은 대상으로 평가하였다. 또한, 의인화의 고-저 수준과 관계없이, 채팅에 비해 음성 인터랙션이 심리적 저항감이 낮았다. 향후 이용 의도에 대해서 의인화 수준과 인터랙션 유형의 상호작용 효과가 발견되었다. 즉, 채팅 인터랙션은 의인화의 효과가 나타나지 않은 반면, 음성 인터랙션의 경우 의인화의 효과가 나타났다. 따라서, 음성 대화형 스마트홈 에이전트는 의인화 수준을 높이는 방향으로 설계가 되어야 사용자들의 지속적 이용을 기대할 수 있다.

• Bulletin of the Korean Chemical Society
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• 제28권6호
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• pp.959-964
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• 2007

The benzene complexes with dimethyl sulfur (DMS) and fluorinated DMS (FDMS) have been investigated using ab initio calculations. The natural bond orbital (NBO) charge population on S atom varies remarkably for different conformations of DMS and FDMS, which determines the possible binding modes for their benzene complexes. The electronegative substituent at the methyl group of DMS causes a significant change in the molecular electrostatic potential around the sulfur atom and changes the interaction mode with aromatic ring. It was found that the sulfur…π interaction mode does not occur in the DMS-benzene complex, while it does in the FDMS-benzene complex. Both B3LYP and MP2 methods provide reliable structures, while the interaction energy obtained by B3LYP is unreliable.

• Structural Engineering and Mechanics
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• 제3권2호
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• pp.107-120
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• 1995

A soil-structure interaction formulation is used here which is based on consideration of the dynamics of the structure with a free, rather than a fixed, base. This approach is shown to give a quite simple procedure for coupling the dynamic characteristics of the structure to those of the foundation and soil in order to obtain a matrix formulation for the complete system. In fixed-base studies it is common to presume that each natural mode of the structure has a given fraction of critical damping, and since the interaction formulation uses a free-base model, it seems natural for this situation to assign the equal modal damping values to free-base modes. It is shown, though, that this gives a structural model which is significantly different than the one having equal modal damping in the fixed-base modes. In particular, it is found that the damping matrix resulting in equal modal damping values for free-based modes will give a very significantly smaller damping value for the fundamental distortional mode of the fixed-base structure. Ignoring this fact could lead one to attribute dynamic effects to interaction which are actually due to the choice of damping.

• 한국지반공학회논문집
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• 제25권6호
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• pp.59-72
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• 2009

대구경 해상 말묵의 수평 하중전이 거동 및 변형 해석을 위해 p-y 하중전이 해석법이 널리 사용되고 있다. 그러나, 본 연구에서는, 기존의 p-y 해석법의 단점을 극복하여, 지반의 연속성을 고려한 수평방향 하중전이 해석을 고찰하였으며, 3D wedge failure mode의 이론적인 해법과 재하시험을 통해 말뚝의 실제 거동에 보다 부합되도록 연약지반의 p-y 곡선을 제안하였다. 제안된 하중전이함수법의 타당성을 검증하기 위하여 현장재하시험 사례와의 비교분석을 수행하였고, 그 결과 제안된 해석방법은 기존 p-y 곡선에 비해 대구경 해상말뚝의 거동 및 변형 특성을 적절히 예측함을 알 수 있었다.

• 한국시뮬레이션학회논문지
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• 제12권2호
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• pp.75-89
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• 2003

This paper describe numerical experiments with solitary beams in a self focusing Kerr medium with fast response. Through formal analogies, it compare this results on the phase sensitivity of beam collision with known predictions about one dimensional soliton interaction. For incoherent oblique beam interaction, there occurs a non-periodic coupled-mode type transfer of energy, resulting in complete transmission each beam through the other one.