• The Journal of Korea Robotics Society
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• v.12 no.3
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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.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.1
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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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• v.14 no.6
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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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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• v.13 no.1
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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.

• Journal of the HCI Society of Korea
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• v.12 no.1
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• pp.15-23
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• 2017

Applying the concept and components of human nature to the conversational agent in the smart home context, this study investigated the effects of the level of anthropomorphism and interaction type on the emotional user experiences and future use intention. The results of experiment study showed that the high-low condition of anthropomorphism and the voice-chatting interaction type have impacts on the perceived closeness, likability, and future use intention. That is, people evaluate the conversational agent as more close, likable, and useful when they perceive more human nature components and when in the voice interaction mode. Psychological resistance was lower in the voice than in the chatting mode regardless of the level of anthropomorphism. The results also demonstrated an interaction effect of anthropomorphism and interaction type on the future use intention: the effect of anthropomorphism existed only in the voice interaction mode. It leads to the conclusion that a conversational agent with the voice recognition interface should be designed with the higher level of human nature components for the continuous use.

• Bulletin of the Korean Chemical Society
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• v.28 no.6
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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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• v.3 no.2
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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.

• Journal of the Korea Society for Simulation
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• v.12 no.2
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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.

• Journal of the Korean Geotechnical Society
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• v.25 no.6
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• pp.59-72
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• 2009

The load distribution and deflection of offshore piles are investigated by lateral load-transfer curve method (p-y curve). Special attention is given to the soil-pile interaction and soil resistance of 3D wedge failure mode. A framework for determining a hyperbolic p-y curve is proposed based on theoretical analysis and experimental load test results. The methods for determining appropriate material parameters needed for constructing the proposed p-y curves are presented in this paper. Through comparisons with field case studies, it was found that the proposed method in the present study estimates reasonably the load transfer behavior of pile, and thus, the computed pile responses, such as bending moment and lateral displacement, agree well with the actual measured responses.