• International Journal of Naval Architecture and Ocean Engineering
• /
• 제8권3호
• /
• pp.277-300
• /
• 2016

The motion of a floating body and the free surface flow are the most important design considerations for ships and offshore platforms. In the present research, a numerical method is developed to simulate the motion of a floating body and the free surface using a fixed rectilinear grid system. The governing equations are the continuity equation and Naviere-Stokes equations. The boundary of a moving body is defined by the interaction points of the body surface and the centerline of a grid. To simulate the free surface the Modified Marker-Density method is implemented. Ships advancing in regular waves, the interaction of waves by a fixed circular cylinder array and the response amplitude operators of an offshore platform are simulated and the results are compared with published research data to check the applicability. The numerical method developed in this research gives results good enough for application to the initial design stage.

• 대한의용생체공학회:의공학회지
• /
• 제20권4호
• /
• pp.485-493
• /
• 1999

Human can generate various posture and motion with nearly 350 muscle pairs. From the viewpoint of mechanisms, the human skeleton mechanism represents great kinematic and dynamical complexity. Physical and behavioral fidelity of human motion requires dynamically accurate modeling and controling. This paper describes a mathematical modeling, and dynamic simulation of human body. The human dynamic model is simplified as a rigid body consisting of 18 actuated degrees of freedom for the real time computation. Complex kinematic chain of human body is partitioned as 6 serial kinematic chains that is, left arm, right arm, support leg, free leg, body, and head. Modeling is developed based on Newton-Euler formulation. The validity of proposed dynamic model, which represents mathematically high order differential equation, is verified through the dynamic simulation.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집A
• /
• pp.510-515
• /
• 2000

Dynamic stability of a flying structure undertaking constant and pulsating axial forces is investigated in this paper. The equations of motion of the structure, which is idealized as a free-free beam, are derived by using the hybrid variable method and the assumed mode method. The structural system includes a directional control unit to obtain the directional stability. The analysis model presented in this paper considers the nonlinear effect due to rigid body motion of the beam. Dynamic stability of the system is influenced by the nonlinear effect. In order to examine the nonlinear effect, first the unstable regions of the linear system are obtained by using the method based upon Floquet's theory, and dynamic responses of the nonlinear system in the unstable region are obtained by using direct time integration method. Dynamic stability of the nonlinear system is determined by the obtained dynamic responses.

• 디지털콘텐츠학회 논문지
• /
• 제18권2호
• /
• pp.283-291
• /
• 2017

가상현실 경험에서 높은 감각적 몰입으로 시각으로 지각되는 정보와 전정기관, 체성감각 등 감각기가 지각하는 정보 간에 불일치가 생기면서 가상현실 멀미가 일어나 기기의 보급에 장애가 되고 있다. 본 연구는 기존의 감각의 충돌 이론에 착안하여 모션 컨트롤러로 대표되는 새로운 전반적인 신체의 움직임이 각성 정도와 현존감에 영향을 끼치며, 가상현실 멀미를 촉발할 수 있고 각성 정도는 감각적 몰입, 현존감과 깊은 관계가 있다는 가설을 세우고 실험을 통해 검증하였다. 특히 컨트롤을 위한 전체적인 신체의 움직임에 집중하여, 몸-머리 움직임과 대조하여 연구하였다. 실험의 결과로 신체 움직임과 각성 정도 간에 유의한 상관관계를 확인할 수 있었고, 현존감에 대해서도 일정 정도 유의한 상관 관계가 있음을 확인할 수 있었다. 또, 신체의 움직임이 있을 때, 안경의 착용 유무가 관측되는 가상현실 멀미에 중재변수로 역할을 하는 것을 확인할 수 있었다.

• 제어로봇시스템학회논문지
• /
• 제15권6호
• /
• pp.626-633
• /
• 2009

A motion planning algorithm is presented in this paper for a commercialized quadruped walking of robot pet. Stable walking is the basic requirement for a commercial-purpose legged robot. In order to secure the walking stability, modified body sway to the centroid of support polygon is addressed. By representation of walking motion with respect to the world coordinate system rather than body coordinate, it is possible to design the several gaits in unified fashion. The initial gait posture is introduced to maximize the stride and to achieve fast walking. The proposed walking motion planning is verified through computer simulation and experiments.

• 한국자동차공학회논문집
• /
• 제14권4호
• /
• pp.92-98
• /
• 2006

In this paper, a planar car model with 3 degrees of freedom was analyzed using the concept of the roll center. To avoid ambiguity, force components which require experimental data were excluded. Only kinematic approach was used to find the position and orientation of the vehicle body and the position of the roll center. The roll center was found by the pole with infinitesimal movement and Kennedy-Aronhold theorem. Centrodes, which are the loci of instantaneous centers of planar motion, were constructed with analyzed results to show characteristics of vehicle body motion. To verify the presented analysis method in this paper, the locus of the roll center and the motion of a 3 D.O.F. planar car model were compared with those of the 1 D.O.F. model.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 추계학술대회 논문집
• /
• pp.91-91
• /
• 2009

Piezoelectric micro-pump should contain the physical running parts like check valves for acquiring the unilateral motion of fluid from the alternating motion of actuators. But the check valves raise many problems such as abrasion or exhaustive destruction by the recursive mechanical displacement To solve these problems, we propose a novle type piezoelectric valveless micro-pump using peristaltic motion due to the traveling wave excitation. Proposed pump model is consisted of two piezoelectric ceramic plates, elastic metal body, caps for covering flow path, rubber rings for sealing tightly and disk springs for the pressurization of pump body.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제8권2호
• /
• pp.75-86
• /
• 2004

In this study, a recursive algorithm for generating the equations of motion of a chain of rigid rods is presented. The methods rests upon the idea of replacing the rigid body by a dynamically equivalent constrained system of particles. The concepts of linear and angular momentums are used to generate the rigid body equations of motion without either introducing any rotational coordinates or the corresponding transformation matrices. For open-chain, the equations of motion are generated recursively along the serial chains. For closed-chain, the system is transformed to open-chain by cutting suitable kinematic joints with the addition of cut-joints kinematic constraints. An example of a closed-chain of rigid rods is chosen to demonstrate the generality and simplicity of the proposed method.

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

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2006년도 제33회 추계학술대회 발표논문집
• /
• pp.86-86
• /
• 2006