• Title/Summary/Keyword: free motion

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3-D analysis of sloshing motion in a fluid container with nonlinear boundary conditions (비선형 경계조건을 고려한 내부 유체의 3차원 자유수면 유동해석)

  • 김문겸;임윤묵;조경환;박종헌;이성민
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2002.03a
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    • pp.177-184
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    • 2002
  • Large amplitude sloshing can occur in contained fluid region due to the seismic ground motion. Also, The pressure by large amplitude sloshing damages the connections between the wall and roof of a fluid container and causes outflow of contained fluid. Therefore, to predict the dynamic behavior accurately, three dimensional analysis with the nonlinear boundary condition must be performed. In this study, the numerical solution procedure is developed using the boundary element method with the Lagrangian particle approach. In order to demonstrate the accuracy and validity of the developed method, the fluid motion for a free oscillation with small amplitude and a forced vibration are analyzed. And the numerical results are compared with the linear theory results and the previous studies with the nonlinear boundary condition.

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A Simulation Model of the ACL Function Using MADYMO (마디모를 이용한 전방십자인대 기능 시뮬레이션 모델)

  • Park, Jung-Hong;Son, Kwon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.11 s.254
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    • pp.1408-1416
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    • 2006
  • A mathematical knee model was constructed using MADYMO. The purpose of this study is to present a more realistic model of the human knee to reproduce human knee motion. Knee ligaments were modeled as line elements and the surrounding muscles were considered as passive restraint elements. A calf-free-drop test was performed to validate the suggested model. A calf was dropped from the rest at about 65 degree flexed posture in the prone position. The motion data were recorded using four video cameras and then three dimensional data were acquired by Kwon3D motion analysis software. The results showed that general shapes of angular quantities were similar in both the experiment and computer simulation. Functional stability of the anterior cruciate ligament was explicitly revealed through this model.

Waveload Analysis for Heeled Barges with Flooded Compartments (손상침수로 자세변화된 바지형 선박의 파랑하중해석)

  • Hong, Do-Chun;Hong, Sa-Young
    • Journal of the Society of Naval Architects of Korea
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    • v.42 no.4 s.142
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    • pp.379-387
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    • 2005
  • A ship may suffer sinkage and heel due to flood in a compartment caused by damage on a deck. The motion and waveloads of the heeled ship floating in waves have been analyzed by making use of a three dimensional potential theory taking account of the hydrodynamic pressure in the flooded compartments. The shear forces and bending moments due to radiation-diffraction waves have been calculated by the direct integration of the 3-d hydrodynamic pressure on the outer and inner hulls of floating barges. The motion responses and the relative flow rate across the mean free surface of the water in the flooded compartments are also presented.

On the Normal Mode Dynamics of a Pendulum Absorber (정규모우드 방법을 활용한 진자형 흡진기의 비선형 동역학에 관한 연구)

  • 심재구;박철희
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.04a
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    • pp.177-183
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    • 1996
  • By utilizing the concept of normal modes, nonlinear dynamics is studied on pendulum dynamic absorber. When the spring mode loses the stability in undamped free system, a dynamic two-well potential is formed in Poincare map. A procedure is formulated to compute the forced responses associated with bifurcating mode and predict double saddle-loop phenomenon. It is found that quasiperiodic motion and stable periodic motion coexist in some parameter ranges, and only periodic motions or rotation of pendulum with chaotic fluctuation are observed in other ranges.

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Internal Resonance and Stability Change for the Two Degree Nonlinear Coupled System (2 자유도 비선형 연성시스템에서 내부공진과 안정성 변화)

  • Kim, Myoung-Gu;Pak, Chul-Hui;Cho, Chong-Du
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.853-861
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    • 2007
  • To understand the concept of dynamic motion in two degree nonlinear coupled system, free vibration not including damping and excitation is investigated with the concept of nonlinear normal mode. Stability analysis of a coupled system is conducted, and the theoretical analysis performed for the bifurcation phenomenon in the system. Bifurcation point is estimated using harmonic balance method. When the bifurcation occurs, the saddle point is always found on Poincare's map. Nonlinear phenomenon result in amplitude modulation near the saddle point and the internal resonance in the system making continuous interchange of energy. If the bifurcation in the normal mode is local, the motion remains stable for a long time even when the total energy is increased in the system. On the other hand, if the bifurcation is global, the motion in the normal mode disappears into the chaos range as the range becomes gradually large.

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VORTEX-INDUCED VIBRATION SIMULATION OF MULTIPLE CIRCULAR CYLINDERS IN LOW REYNOLDS NUMBER FLOWS USING CARTESIAN MESHES (직교 격자를 이용한 저 레이놀즈 수 유동장내 다중 배치된 실린더의 와유기 진동 해석)

  • Han, Myung-Ryoon;Ahn, Hyung-Teak
    • Journal of computational fluids engineering
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    • v.16 no.1
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    • pp.73-82
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    • 2011
  • In this paper, the vortex-induced vibration of circular cylinders is studied using the immersed boundary method on the Cartesian mesh. The Reynolds numbers considered is from 100 to 200. Using the configuration of tendemly arranged multiple circular cylinders, the vortex shedding behind of the cylinders and their flow-induced motion are investigated. The staggered MAC grid arrangement, which is the typical grid system for the incompressible flow on the Cartesian meshes, is utilized. Pressure correction method is applied for solving the divergence-free incompressible velocity field. The body motion is described by immersed boundary technique that has advantages for moving object on the fixed computational domain. It is also discussed for the computational noise in hydrodynamic forces when body motion is represented by the immersed boundary method. The Predictor/Corrector method is used for simulating the nonlinear response of the elastically mounted cylinder excited by vortex-shedding.

A Lane Based Obstacle Avoidance Method for Mobile Robot Navigation

  • Ko, Nak-Yong;Reid G. Simmons;Kim, Koung-Suk
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1693-1703
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    • 2003
  • This paper presents a new local obstacle avoidance method for indoor mobile robots. The method uses a new directional approach called the Lane Method. The Lane Method is combined with a velocity space method i.e., the Curvature-Velocity Method to form the Lane-Curvature Method (LCM). The Lane Method divides the work area into lanes, and then chooses the best lane to follow to optimize travel along a desired goal heading. A local heading is then calculated for entering and following the best lane, and CVM uses this local heading to determine the optimal translational and rotational velocities, considering some physical limitations and environmental constraint. By combining both the directional and velocity space methods, LCM yields safe collision-free motion as well as smooth motion taking the physical limitations of the robot motion into account.

Human Motion Control Using Dynamic Model (동력학 모델을 이용한 인체 동작 제어)

  • Kim, Chang-Hoe;O, Byeong-Ju;Kim, Seung-Ho
    • Journal of the Ergonomics Society of Korea
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    • v.18 no.3
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    • pp.141-152
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    • 1999
  • In this paper, We performed the human body dynamic modelling for the realistic animation based on the dynamical behavior of human body, and designed controller for the effective control of complicate human dynamic model. The human body was simplified as a rigid body which consists of 18 actuated degrees of freedom for the real time computation. Complex human kinematic mechanism was regarded as a composition of 6 serial kinematic chains : left arm, right arm, support leg, free leg, body, and head. Based on the this kinematic analysis, dynamic model of human body was determined using Newton-Euler formulation recursively. The balance controller was designed in order to control the nonlinear dynamics model of human body. The effectiveness of designed controller was examined by the graphical simulation of human walking motion. The simulation results were compared with the model base control results. And it was demonstrated that, the balance controller showed better performance in mimicking the dynamic motion of human walking.

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Collision-avoidance path planning for spray painting robots (페인팅로보트의 충돌회피 경로계획)

  • 이정재;서석환
    • 제어로봇시스템학회:학술대회논문집
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    • 1991.10a
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    • pp.545-550
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    • 1991
  • Recently, the use of robots for painting operations has received much attention, as it is a powerful means for automation and quality improvement. Collision-avoidance is a key issue in the path planning for painting operations. In this paper, we develop a computationally efficient algorithm for the generation of collision-free path for two types of motion: a) Gross motion when the robot approaches the painting area, and b) Fine motion while spraying the surface. The former is a typical collision-avoidance problem, but the latter calls for special attention as the painting mechanics has to be incorporated into path planning. The developed algorithm is applied for the internal coating of the car body whose structure is the major source of collision.

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Robot motion planning for time-varying obstacle avoidance using view-time concept ('관측 시간'개념을 이용한 로보트의 시변 장애물 회피 동작 계획)

  • 고낙용;이범희;고명삼;남윤석
    • 제어로봇시스템학회:학술대회논문집
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    • 1991.10a
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    • pp.1040-1045
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    • 1991
  • An approach to time-varying obstacle avoidance problem is pursued. The mathematical formulation of the problem is given in Cartesian space and in joint space. To deal with the time-varying obstacles, view-time is introduced. A view-time is the time interval viewing the time-varying obstacles to model equivalent stationary obstacles. For the analysis of the properties of the view-time, avoidability measure is defined as a measure of easiness for a robot to avoid obstacles. Based on the properties, a motion planning strategy to avoid time-varying obstacles is derived. An application of the strategy to the collision-free motion planning of two SCARA robots and the simulation on the application are given.

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