• 대한기계학회논문집
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• 제18권12호
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• pp.3270-3275
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• 1994

Particle trajectory visualization using laser sheet was performed to investigate the corona wind flow interactions in the one-wire and two-wire type electrostatic precipitators. The corona wind generated by corona discharge was not negligible, and strong flow interactions took place owing to the induced circulatory cells. In the case of one-wire type, as the applied voltage was increased and the cross-section mean velocity was decreased, the effect of corona wind became active. In the case of two-wire type, if upstream discharge voltage was relatively higher than downstream discharge voltage, the effect of upstream corona wind was reduced.

• 대한기계학회논문집B
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• 제24권3호
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• pp.477-484
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• 2000

Microcontamination caused by particle deposition on the head disk interface threatens the reliability of hard disk drive. Design of slider rail to control contamination becomes an important issue in magnetic recording. In this paper, how particles adhere to the slider and the disk is examined. To investigate accumulation mechanism of the particles, trajectory of the particles in a slider/disk interface is simulated with considering various forces including drag force, gravitational force, Saffman lift force, and electrostatic force. It is found that the charged particles can easily adhere to the slider or disk surface, if an electric field exists between the slider and the disk. It is supposed that the vertical motion of the particles should be related with not only Saffman force but also electrostatic force.

• 한국항행학회논문지
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• 제24권5호
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• pp.382-392
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• 2020

드론기술은 민수용과 군사용 양 분야 에서 전도유망한 기술이나, 규정과 관련법의 미성숙으로 불법드론이 오남용 되고, 사회안전에 심각한 위협이 되고 있다. 본고에서는 PSO (particle swarm optimization)에 기반을 둔 군집드론 궤적계획기를 개발하여, 군집정찰드론들에게 최적화된 3차원 궤적탐지기술을 제공한다. 나아가서, 에너지소비도, 비행위험도 및 SAP (surveillance area priority)와 부합하는 군집 목적물 최적화 함수를 제시하고 평가한다. 군집 비행 시뮬레이션 결과는, 제안한 궤적계획기로 생성한 궤적은 에너지 소비도 및 비행위험도를 최소화 하며 탐색한다는 것을 입증해준다.

• 로봇학회논문지
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• 제8권2호
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• pp.92-103
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• 2013

Humanoid robot is the most intimate robot platform suitable for human interaction and services. Biped walking is its basic locomotion method, which is performed with combination of joint actuator's rotations in the lower extremity. The present work employs humanoid robot simulator and numerical optimization method to generate optimal joint trajectories for biped walking. The simulator is developed with Matlab based on the robot structure constructed with the Denavit-Hartenberg (DH) convention. Particle swarm optimization method minimizes the cost function for biped walking associated with performance index such as altitude trajectory of clearance foot and stability index concerning zero moment point (ZMP) trajectory. In this paper, instead of checking whether ZMP's position is inside the stable region or not, reference ZMP trajectory is approximately configured with feature points by which piece-wise linear trajectory can be drawn, and difference of reference ZMP and actual one at each sampling time is added to the cost function. The optimized joint trajectories realize three phases of stable gait including initial, periodic, and final steps. For validation of the proposed approach, a small-sized humanoid robot named DARwIn-OP is commanded to walk with the optimized joint trajectories, and the walking result is successful.

• 한국유체기계학회 논문집
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• 제5권1호
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• pp.7-12
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• 2002

As the first step to investigate the fundamental mechanism of a dispersed two-phase flow, we studied the detailed interactions between bubble or particle motion and flow around it. Experiments were carried out with a rising bubble or particle in stagnant water in a vertical pipe. Particles with different densities, and/or different shapes were used for comparison with a bubble. We adopted 3D-PTV (Three-Dimensional Particle Tracking Velocimetry) for measuring the bubble or particle motions, and PIV (Particle Image Velocimetry) for measuring the water flow simultaneously (Hybrid PIV). The experimental results showed that the oblate spheroidal solid particle rose along the longer axis direction at the point that the inclination of the longer axis reached the maximum, and the inclination direction changed after moving. The bubble moved to the direction that the spheroid's projected width grew up to the largest, and the minor axis of the oblate spheroidal body of the bubble was parallel to the moving direction. The trajectory of the center of the particle/bubble which was measured with 3D-PTV, was marked on the section (x-y) of the pipe. It exhibited the pattern of the particle/bubble motion.

• 드라이브 ㆍ 컨트롤
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• 제15권3호
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• pp.1-7
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• 2018

Humanoid robots have fascinated many researchers since they appeared decades ago. For the requirement of both accurate tracking control and the safety of physical human-robot interaction, torque control is basically desirable for humanoid robots. Humanoid robots are highly nonlinear, coupled, complex systems, accordingly the calculation of robot model is difficult and even impossible if precise model of the humanoid robots are unknown. Therefore, it is difficult to control using traditional model-based techniques. To realize model-free torque control, time-delay control (TDC) for humanoid robot was proposed with time-delay estimation technique. Using optimal walking trajectory obtained by particle swarm optimization, TDC with proposed scheme is implemented on whole body of a humanoid, not on biped legs even though it is performed by a virtual humanoid robot. The simulation results show the validity of the proposed TDC for humanoid robots.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2312-2320
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• 2005

The aerodynamic effects of leading-edge accretion can raise important safety concerns since the formulation of ice causes severe degradation in aerodynamic performance as compared with the clean airfoil. The objective of this study is to develop a numerical simulation strategy for predicting the particle trajectory around an MS-0317 airfoil in the test section of the NASA Glenn Icing Research Tunnel and to investigate the impingement characteristics of droplets on the airfoil surface. In particular, predictions of the mean velocity and turbulence diffusion using turbulent flow solver and Continuous Random Walk method were desired throughout this flow domain in order to investigate droplet dispersion. The collection efficiency distributions over the airfoil surface in simulations with different numbers of droplets, various integration time-steps and particle sizes were compared with experimental data. The large droplet impingement data indicated the trends in impingement characteristics with respect to particle size ; the maximum collection efficiency located at the upper surface near the leading edge, and the maximum value and total collection efficiency were increased as the particle size was increased. The extent of the area impinged on by particles also increased with the increment of the particle size, which is similar as compared with experimental data.

• 한국산업융합학회 논문집
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• 제19권4호
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• pp.167-175
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• 2016

We present a method for improving adaptability of Learning from Demonstration (LfD) strategy by combining the LfD and Particle Swarm Optimization (PSO). A trajectory generated from an LfD is modified with PSO by minimizing a fitness function that considers constraints. Finally, the final trajectory is suitable for a task and adapted for constraints. The effectiveness of the method is shown with a target reaching task with a manipulator in three-dimensional space.

• 한국결정성장학회지
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• 제13권3호
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• pp.145-151
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• 2003

전산유체역학을 이용하여 전형적인 구조를 갖는 사이클론 분리기 시스템 내에서의 주입 가스 유동 및 입자 거 동해석을 통해 가스 주입 유속에 따른 입자 거동 양상을 3차원적으로 해석하였다. 해석 결과는 Navier-stokes 방정식을 이용한 유체 유동 현상과 Lagrangian 접근법을 이용한 입자 거동 경로 추적을 결합시켜 도출되었다. 주입 유속이 증가함에 따라 내부 압력 손실이 증가하였고 이런 내부 압력 변화는 분리기 내의 유체의 유동 양상에 영향을 미쳤다. 입자의 거동은 유체의 유동에 의해 결정되었으며 일정 유속에 대해서는 입자의 크기에 크게 의존하였다. 그리고 주입 유속의 증가는 입자의 경로를 증가시키면서 분리기의 하부 영역으로 이동시켰다. 이로 인해 분리기내에 존재하는 입자의 최소 크기가 작아지며 일정 크기의 입자의 경우 분리율이 증가하였다. 결론적으로 가스 유입 유속의 변화는 내부의 유체 유동 변화와 입자 거동 양상에 중요한 요인이 된다.

• 대한원격탐사학회지
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• 제30권1호
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• pp.13-24
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• 2014

인공위성 원격탐사 자료는 화산재 모니터링을 위한 중요한 도구로서 사용되어 왔다. 본 연구는 최근에 발생한 주요 화산폭발 사례(2008년 Chait$\acute{e}$n 화산, 2010년 Eyjafjallaj$\ddot{o}$kull 화산, 2011년 Shinmoedake 화산)를 대상으로 인공위성자료를 이용한 화산재 모니터링과 궤적분석 모델링을 수행하였다. 이를 위하여 Moderate Resolution Imaging Spectro-radiometer(MODIS) 인공위성 관측자료로부터 적외선 밝기온도차 기법을 적용하여 산출된 화산재 탐지 산출물과 HYbrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT) 모델을 이용한 전진궤적분석자료를 상호 비교하였다. 그 결과, 인공위성을 이용한 화산재 탐지 산출물은 모델링한 궤적분석 결과와 상호간에 관련성이 높게 나타났다. 이러한 결과는 인공위성 관측자료와 모델링의 통합분석자료가 화산재 감시 및 예측을 위하여 중요한 역할을 수행할 수 있는 가능성을 제시한다.