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자유수면의 경계면에서 해의 번짐을 줄이기 위한 경계면 압축 기법 및 주상체에의 적용
이희범(H. Lee),이신형(S. H. Rhee),김동진(D. J. Kim),김선영(S. Y. Kim),박선호(S. Park) 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.5
A high speed planing hull is mostly supported by hydrodynamic lift force rather than buoyancy force. The lift force directly influences the running attitude of the planing hull such as trim and sinkage. And the pressure distribution is strongly related to the solution of a free-surface flow around a planing hull. To handle free-surface flow volume-of-fluid (VOF) method have been widely used even it has a disadvantages of interface smearing. In the present study, a new dynamic interface compression method were introduced to reduce interface smearing and avoid unphysical solution. The dynamic compression consists of a function of angle of the flow direction and free-surface. The method was implemented and validated by prismatic body problem.
자유수면 유동 해석을 위한 경계면 포착 기법들에 대한 비교 연구
이희범(H.B. Lee),이신형(S.H. Rhee) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
To analyze flow around a floating body such as ships or floating structures, free-surface flow should be considered. In the present study, free-surface solution methods were implemented in SNUFOAM,which is based on the open source CFD library OpenFOAM. In SNUFOAM, volume-of-fluid (VOF) method, which uses high resolution differencing schemes to preserve both the sharpness of interface and boundedness of volume fraction was adopted for free-surface flows. In the code, several high resolution differencing schemes such as CICSAM, HR1C, M-CICSAM and modified HRIC were implemented and tested. The schemes were verified by Rudman translation test and Zalesak slotted disk test which are the canonical benchmarking test for VOF schemes. The schemes were also tested by dam breaking problem, sloshing problem and Reyleigh Taylor instability problem. From the results, the schemes were implemented well to SNUFOAM.
샘플링 기법의 보완을 통한 RRT<SUP>*</SUP> 기반 온라인 이동 계획의 성능 개선
이희범(Hee Beom Lee),곽휘권(HwyKuen Kwak),김준원(JoonWon Kim),이춘우(ChoonWoo Lee),김현진(H.Jin Kim) 제어로봇시스템학회 2016 제어·로봇·시스템학회 논문지 Vol.22 No.3
Motion planning problem is still one of the important issues in robotic applications. In many real-time motion planning problems, it is advisable to find a feasible solution quickly and improve the found solution toward the optimal one before the previously-arranged motion plan ends. For such reasons, sampling-based approaches are becoming popular for real-time application. Especially the use of a rapidly exploring random tree<SUP>*</SUP> (RRT<SUP><SUP>*</SUP></SUP>) algorithm is attractive in real-time application, because it is possible to approach an optimal solution by iterating itself. This paper presents a modified version of informed RRT<SUP>*</SUP> which is an extended version of RRT<SUP>*</SUP> to increase the rate of convergence to optimal solution by improving the sampling method of RRT<SUP>*</SUP>. In online motion planning, the robot plans a path while simultaneously moving along the planned path. Therefore, the part of the path near the robot is less likely to be sampled extensively. For a better solution in online motion planning, we modified the sampling method of informed RRT<SUP>*</SUP> by combining with the sampling method to improve the path nearby robot. With comparison among basic RRT<SUP>*</SUP>, informed RRT<SUP>*</SUP> and the proposed RRT<SUP>*</SUP> in online motion planning, the proposed RRT<SUP>*</SUP> showed the best result by representing the closest solution to optimum.
중형트럭 현가계의 설계변수 변화에 따른 피칭운동이 민감도 해석
이희범(H.B.Lee),이기호(G.H.Lee),김태식(T.S.Kim),손한규(H.G.Sohn) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
Ride quality of medium truck became an important item, due to increase the standard of life style. This study describes how to determine and evaluate design parameters related to chassis suspension system through time and frequency analysis. The spring stiffness and damping force of the chassis suspension system were obtained by the magnitude of the vertical acceleration PSD. The simulation was carried out on the various road profile, which is suggested by ISO. The body pitching of medium truck item which should be studied for ride quality. We made truck model by use of DADS, which is dynamic analysis software, in order to find out the truck motions. From the results of sensitivity analysis of suspension parameters,we found out that, the spring and shock absorber affect the pitching of the medium truck. In order to truck model validation, We carried out actual test.<br/>
토우 궤적 변화에 의한 미니 버스 차량의 방향 안정성 연구
이희범(H.B.Lee),안찬우(C.W.Ahn) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_2
In this paper, we discuss the directional stability of a Mini-bus with varying suspension design parameters. We analyzed the vehicle behavior during the cornering in a transient steering condition. We made a vehicle model by use of DADS, which is dynamic analysis software, in order to carry out many cases of simulation with varying design parameters. The effect of toe-geometry change to vehicle stability is evaluated by computer simulation and the actual test. In order to reduce the under steer characteristics of a mini-bus, the amount of toe geometry change should be less than current value.<br/>