• 대한조선학회논문집
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• 제53권5호
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• pp.388-399
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• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.

• 한국CDE학회논문집
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• 제2권1호
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• pp.60-67
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• 1997

CAD systems offer a variety of techniques for designing and rendering models of static 3D objects and even of mechanisms, but relatively few tools exist for interactively specifying arbitrary movements of rigid bodies through space. Such tools are essential, not only for artistic animation, but also, for planning and demonstrating assembly and disassembly procedure of manufactured products. A rigid body motion is a continuous mapping from the time domain to a set of positions. To relieve the designers from the burden of specifying this mapping in abstract mathematical terms, combinations of simple rigid motion primitives, such as linear translations or constant axis rotations, are often used. These simple motions are planar and thus ill-suited for approximating arbitrary motions in 3D-space. Instead, we propose the screw motion primitive, a special combination of linear translations and constant axis rotations, which has a simple geometric representation that can be automatically and unambiguously computed from the starting and ending positions of the moving body. Although, any two positions may be interpolated by an infinity of motions, we chose the screw motion for its relative generality and its computational advantages. The paper covers original algorithms for computing the screw motions from interpolated positions and envelopes of swept regions to predict collisions.

• 한국소음진동공학회논문집
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• 제21권11호
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• pp.1043-1050
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• 2011

This paper presents practical results for the estimation of vibration level inside a powertrain based on the rigid body theory and measurement. The vibration level of inside powertrain has been used for the calculation of excitation force of an engine indirectly. However it was difficult to estimate or measure the vibration level inside of a powertrain when a powertrain works on the driving condition of a vehicle. To do this work, the rigid body theory is employed. At the first, the vibration on the surface of a powertrain is measured and its results are secondly used for the estimation the vibration level inside of powertrain together with rigid body theory. Also did research on how to decrease the error rate when the rigid body theory is applied. This method is successfully applied to the estimation of the vibration level on arbitrary point of powertrain on the driving condition at the road.

• Journal of Mechanical Science and Technology
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• 제19권4호
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• pp.976-984
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• 2005

This paper presents the analysis results of dynamics in the billiards game within the frame­work of rigid-body mechanics and a numerical simulation program. The friction exists between the ball and the table bed as well as between the ball and the rail. There are three parts in the dynamic behavior of the ball on the table bed; motion of the ball on the table bed, collision between balls, and collision between the ball and the cushion. During the development of the simulation program, the dynamics problems such as rolling motion and three-dimensional frictional impact motion have been analyzed in detail. The theoretical issues are implemented into a viable graphic simulation program and its efficacy is demonstrated through the experi­mental validation of the billiards game. The resulting analysis results are verified quantitatively and qualitatively using high-speed video camera. Through the experimental tests, it was found that the physical parameters such as coefficients of restitution and friction vary according to the motion variables and corresponding empirical formulations were developed. The simulation and experimental results agree well.

• Structural Engineering and Mechanics
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• 제29권4호
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• pp.433-453
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• 2008

The equation of motion of a one way (vertical) spanning strip wall, as an assembly of two rigid bodies, is presented. Only one degree of freedom is needed to completely describe the wall response as the bodies are assumed to be perfectly rectangular and are allowed to rock but not to slide horizontally. Furthermore, no arching action occurs since vertical motion of the upper body is not restrained. Consequently, the equation of motion is nonlinear, with non constant coefficients and a Coriolis acceleration term. Phenomena associated with overburden to self weight ratio, motion triggering, impulsive energy dissipation, amplitude dependency of damping and period of vibration, and scale effect are discussed, contributing to a more complete understanding of experimental observations and to an estimation of system parameters based on the wall characteristics, such as intermediate hinge height and energy damping, necessary to perform nonlinear time history analyses. A comparison to a simple standing, or parapet, wall is developed in order to better highlight the characteristics of this assembly.

• 대한기계학회논문집A
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• 제24권1호
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• pp.232-239
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• 2000

The paper describes the parametric instability of free-free beams subjected to a controlled pulsating follower force. The beam has a tip rigid body not a mass point, and the direction of pulsating follower force is controlled by the direction control sensor. Equations of motion are derived by Hamilton's principle and the instability regions are obtained by finite element formulation. The effects of magnitude, rotary inertia, the distance between free end of the beam and the center of gravity of the rigid body on the instability types and regions are investigated by the change of the constant and periodic part of the follower force.

• 제어로봇시스템학회논문지
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• 제16권4호
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• pp.391-395
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• 2010

In our paper, we propose an asymmetric single-tracked wheel system, and describe its structure and the method for maintaining the length of a transformable track system. And the method is reducing the gap of lengths. Therefore, we propose an efficient structure for transforming and explain motions with kinematics. Our transformable shape single-tracked mobile system has an advantage to overcome an obstacle or stairs by the variable arms in the single unity track system. But we will make the variable shape of tracked system get a drive that has a force to stand against a wall. In this case, we can consider this system to a rigid body and have a notice that this single tracked system is able to get vary shape with the variable arm angle. Considering forces balance along x-axis and y-axis, and moments balance around the center of the mass we have. If this rigid body is standing against a wall and doesn't put in motion, the force of flat ground and the rigid body sets an equal by a friction. In the same way, the force of a wall and the rigid sets an equal by a friction.

• 한국산업융합학회 논문집
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• 제20권5호
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• pp.405-410
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• 2017

This paper deals with 3D simulation of industrial robot for automated manufacturing system. In order to evaluate the operational characteristics of the industrial robot system in the worst case motion scenario, flexible - rigid multibody analysis was performed. Then, the rigid body dynamics analysis was performed and the results were compared with the flexible - rigid multibody analysis. Modal analysis was also performed to confirm the dynamic characteristics of the robot system. In the case of the flexible-rigid multibody simulation, only the structural members of interest were modeled as elastic bodies to confirm the stress state. The remaining structural members were modeled as rigid bodies to reduce computer resources.

• 한국컴퓨터그래픽스학회논문지
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• 제29권3호
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• pp.69-77
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• 2023

본 연구는 몰입형 가상환경에서의 가상현실 사용자의 사회적 현존감을 높이고 다양한 경험을 제공하기 위하여 강체 추적 기반의 가상 아바타 응용 방법을 제안한다. 제안하는 방법은 마커를 사용한 모션 캡처 기반의 실시간 강체 추적을 기반으로 역운동학을 통해 가상 아바타의 동작을 추정한다. 이를 통해 현실 세계에서의 간단한 객체 조작으로 몰입감 높은 가상환경을 설계함을 목적으로 한다. 가상 아바타를 통한 몰입형 가상환경에 관한 응용을 실험 및 분석하기 위하여 과학실험 교육 콘텐츠를 제작하고 시청각 교육, 전신 추적, 그리고 제안하는 강체 추적 방법과의 설문을 통해 비교 분석하였다. 제안한 가상환경에서 참가자들은 가상현실 HMD를 착용하고 추정된 동작으로부터 실험 교육 행동을 수행하는 가상 아바타로부터 몰입과 교육 효과를 확인하기 위한 설문을 진행하였다. 결과적으로 강체 추적 기반의 가상 아바타를 활용하는 방법을 통해 전통적인 시청각 교육보다 높은 몰입과 교육 효과를 유도할 수 있었으며, 전신 추적을 위한 많은 작업 없이도 충분히 긍정적인 경험을 제공할 수 있음을 확인하였다.

• 한국통신학회논문지
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• 제15권4호
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• pp.301-314
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• 1990

본 논문은 시각 패턴 인식 기법을 이용하여 보이지 않는 강체의 운동을 해석하고자 한다. 가려져 보이지 않는 강체에 특수 모양의 강체를 부착하여 볼 수 있게 한 다음, 강체의 운동을 비디오 카메라로 포착한다. 모든 운동은 평행 이동과 회전 이동으로 나타낼 수 있다. 그러나 평행 이동도 무한 원점을 중심으로 한 회전 운동으로 표현할 수가 있다. 따라서, 운동 해석은 순간 회전 중심과 회전각을 구하는 것이다. 구현한 알고리즘은 인체의 하악 운동에 적용 시켰다.