• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1024-1040
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• 2014

The theoretical background and a numerical solution procedure for a time domain hydroelastic code are presented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solver where the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in a local floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frame undergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preserves the coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide the total fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forces and the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show that the VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responses accurately.

• 한국컴퓨터그래픽스학회논문지
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• 제2권1호
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• pp.48-60
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• 1996

이 논문은 실감나는 컴퓨터 그래픽 애니매이션을 하기위한 새로운 방법을 제시하는데, 이것은 forward dynamic simulation 과 비선형 방정식 해법을 사용한 것이다. 이 방법을 사용하여 시뮬래이션할 경우, 물리학적 기하학적 기구학적 제약을 쉽게 만족시킬 수 있다. 이러한 forward dynamic simulation 기법은 특히 비 자발적인 동작에 대하여 아주 실감나는 동작을 제공한다. 이러한 시뮬래이션 기법에 비선형 방정식 해법을 사용하여 컴퓨터 그래픽 애니매이션 기법을 만든다. 기본적인 방법은 동작 제어 기능을 추가하여 사용자가 애니매이션 하고자 하는 목적을 만족 시키는 것인데, 비선형 함수의 문제로 변환하여 최적값만 찾으면 되는 것이다. 이러한 forward dynamic simulation 을 사용한 애니매이션을 작동기를 가진 경우와, 작동기를 가지지 않은 경우로 나누어 두개의 제어방법을 제시하는데, 특히 선형 작동기(근육)를 가진 경우에 대하여 보다 현실에 가까운 제어법을 제시한다. 이상의 두 동작 제어에 관한 예를 "마술주사위" 와 "사람의 일어섬" 예로 보여준다.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2436-2441
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• 2002

Finite element technique considering adhesive forces is proposed and applied to analyze the behavior of elastic hemispherical asperity adhesively contacting the plane surface of semi -infinite rigid body. It is demonstrated that the finite element model simulates interfacial phenomena such as jump -to-contact and adhesion hysteresis that cannot be simulated with the currently available adhesive contact continuum models. This simulation aiso provides valuable information on contact pressure, contact region and stress distributions. This technique is anticipated to be utilized in designing a low-adhesion surface profile for MEMS/NEMS applications since various contact geometries can be analyzed with this technique.

• 소음진동
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• 제7권2호
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• pp.261-272
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• 1997

Recently washing machines are to be in lower vibration and lower sound because of better environment. Vibration problems in washing machines occur in both washing mode and spinning mode, but vibration in spinning mode becomes main problem because of its high rotating speed and continuity. Vibration while spinning is mainly due to rigid body motion of total washing system which includes suspending rods, washing bath, spinning bath, and gear sets. In this study, some researches were done in order to analyze the rigid body motion of washing system and flexible vibration of spinning bath. A basic mathematical model was established, and the effect of position of salt water and shape change of salt water case were considered. And the effect of lengths of suspending rods, attaching angles, vertical and horizontal position, stiffness of spring on the change of vibration were also considered. To identify the effect of salt water on vibration, some measurements were done. When salt water was positioned at upper part, the effect was most and this coincides with the tendency of simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2092-2095
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• 2001

In this paper, the performance of a new alternative form of three-axis attitude estimation algorithm for a rigid body is evaluated via simulation for the situation where the observed vectors are the estimated baselines of a GPS antenna array. This method is derived based on a simple iterative nonlinear least-squares with four elements of quaternion parameter. The representation of quaternion parameters for three-axis attitude of a rigid body is free from singularity problem. The performance of the proposed algorithm is compared with other eight existing methods, such as, Transformation Method (TM), Vector Observation Method (VOM), TRIAD algorithm, two versions of QUaternion ESTimator (QUEST), Singular Value Decomposition (SVD) method, Fast Optimal Attitude Matrix (FOAM), Slower Optimal Matrix Algorithm (SOMA).

• International Journal of Precision Engineering and Manufacturing
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• 제5권4호
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• pp.50-60
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• 2004

A very flexible beam can be used to model various types of continuous mechanical parts such as cables and wires. In this paper, the dynamic properties of a very flexible beam, included in a multibody system, are analyzed using absolute nodal coordinates formulation, which is based on finite element procedures, and the general continuum mechanics theory to represent the elastic forces. In order to consider the dynamic interaction between a continuous large deformable beam and a rigid multibody system, a combined system equations of motion is derived by adopting absolute nodal coordinates and rigid body coordinates. Using the derived system equation, a computation method for the dynamic stress during flexible multibody simulation is presented based on Euler-Bernoulli beam theory, and its reliability is verified by a commercial program NASTRAN. This method is significant in that the structural and multibody dynamics models can be unified into one numerical system. In addition, to analyze a multibody system including a very flexible beam, formulations for the sliding joint between a very deformable beam and a rigid body are derived using a non-generalized coordinate, which has no inertia or forces associated with it. In particular, a very flexible catenary cable on which a multibody system moves along its length is presented as a numerical example.

• 대한의용생체공학회:의공학회지
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• 제25권4호
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• pp.283-288
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• 2004

본 논문에서는 작은 여성 승객의 충돌해석을 위한 유한요소 모델링에 대하여 Part I 의 분절된 강체 모델에 이어 소개하고 있다. 추가로 모델링 된 상세한 팔, 다리 및 내부 요소들이 분절된 강체 모델에 합체되어 충돌 상해 즉 골절 또는 탈골 등을 예측하게 된다. 이러한 사지 및 내부 요소들의 거동 특성은 확보된 사체 실험 결과와 비교, 검증하였다. 따라서 본 논문에서 제안하고 있는 작은 여성 인체 모델은 충돌 상해 기구학의 조사 및 현존하는 충돌 더미의 생체 충실도를 보완하는데 활용될 수 있다.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2201-2210
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• 2000

Vibration of a rotating disk-spindle system is analyzed by using Hamilton's principle, FEM and substructure synthesis. A rotating disk undergoes the rigid body motion and the elastic deformation. It s equation of motion is derived by Kirchhoff plate theory and von Karman nonlinear strain. A rotating shaft is described by Rayleigh beam theory considering the axial rigid body motion. The stationay shaft supporting the rotating disk-spindle-bearing system is modeled by Euler beam theory, and the stiffness of ball bearing is determined by A.B.Jones' theory. FEM is used to solve the derived governing equations, and substructure synthesis is introduced to assemble each structure of the rotating disk-spindle system. The developed theory is applied to the spindle system of a 35' computer hard disk drive with 3 disks to verify the simulation results. The simulation results agree very well with the experimental ones. The proposed theory may be effectively expanded to the complex structure of a disk-spindle system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.573-576
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• 2005

This research presents a three-dimensional modeling technique for a flexible sheet. A relative coordinate formulation is used to represent the kinematics of the sheet. The three-dimensional flexible sheet is modeled by multi-rigid bodies interconnected by out-of-plane joints and plate force elements. A parent node is designated as a master body and is connected to the ground by a floating joint to cover the rigid motion of the flexible sheet in space. Since the in-plane deformation of a sheet such as a paper and a film is relatively small, compared to out-of-plane deformation, only the out-of-plane deformation is accounted for in this research. The recursive formulation has been adopted to solve the equations of motion efficiently. An example is presented to show the validity of the proposed method.

• 제어로봇시스템학회논문지
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• 제10권8호
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• pp.703-710
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• 2004

This paper presents discontinuous zigzag gait analysis for a newly modeled quadruped walking robot with an articulated spine which connects the front and rear parts of the body. An articulated spine walking robot can move easily from side to side, which is an important feature to guarantee a larger gait stability margin than that of a conventional single rigid-body walking robot. First, we suggest a kinematic modeling of an articulated spine robot which has new parameters such as a waist-joint angle, a rotate angle of a front and rear body and describe characteristics of gait using an articulated spine. Next, we compared the difference of walking motion of newly modeled robot with that of a single rigid-body robot and analyzed the gait of an articulated spine robot using new parameters. On the basis of above result, we proposed a best walking motion with maximum stability margin. To show the effectiveness of proposed gait planning by simulation, firstly the fastest walking motion is identified based on the maximum stride, because the longer the stride, the faster the walking speed. Next, the gait stability margin variation of an articulated spine robot is compared according to the allowable waist-joint angle.