RTK GPS를 이용한 오픈소스 아두파일럿 기반 OmniX 보트의 자율주행 경로 추적성에 관한 연구

안남현,구본국,박희승,장호윤,An, Nam-Hyun,Gu, Bon-Kuk,Park, Hui-Seung,Jang, Ho-Yun 해양환경안전학회 2021 해양환경안전학회지 Vol.27 No.6

The IoT (Internet of Things) technology is rapidly becoming an important consideration in many engineering fields in the current 4th industrial era. In recent years, the concepts of digital shipbuilding and smart factories have been adopted as trends in shipyards. However, there is active interest in research on implementing autonomous driving in autonomous vehicles and airplanes, which is currently available in commercial form in a limited capacity. The present study is regarding the path-tracking performance of a boat to accomplish an autonomous driving mission using a flight controller (FC) and real-time kinematic (RTK) global positioning system (GPS) based on an open-source Ardupilot; an actual sea test is also performed using this system on a calm lake. The boat's mission is to evaluate the maneuverability of the self-driving process to a specific point and returning to the home position. For a given speed, the difference between the preset mission trajectory and actual operational trajectory was analyzed, and a series of studies were conducted on the applicability of the system to ships. In addition, the movements and maneuverability of the OmniX-type hull with four propellers were investigated, and the driving path-tracking performance was observed to increase by a maximum of 48%.

외부경계층 수직 날의 저항저감효과에 대한 실험적 연구

안남현(Nam Hyun An),전호환(Ho Hwan Chun),이인원(Inwon Lee) 대한조선학회 2008 대한조선학회 논문집 Vol.45 No.5

An experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first devised by Hutchins (2003). The drag reduction efficiency of the blades was reported to reach as much as 30%. The assessment of the drag reducing efficiency is mainly restricted to the downstream region of the blades. Indeed, sufficient care has not been taken to such adverse effects as the increase in the wetted surface area and the flow disturbances due to the presence of the blades. In the present study, a series of drag force measurements in towing tank and circulating water channel has been performed toward the assessments of the total drag reduction efficiency of the outer-layer vertical blades.

POD 기법을 이용한 경계층 외부 수직날의 마찰저항 저감 기구에 관한 관측

안남현(Nam Hyun An),박성현(Seong Hyeon Park),전호환(Ho Hwan Chun),이인원(Inwon Lee) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.6

외부경계층 수직 날의 마찰저항 저감 기구를 규명하기 위하여 회류수조에서 시간분해 입자영상유속계로 측정된 비정상 유동장에 POD 분석을 실시하였다. 최근의 PIV 결과에서는 수직날 평면 및 수직날 사이 평면에서 각각 2.73%, 7.95%의 마찰저항 저감효과가 발견되었다. 본 연구에서는 수직날 배열이 난류조직구조에 미치는 영향을 POD 방법을 통하여 분석하였다. 난류유동의 조직적인 와구조가 수직날에 의하여 절단, 변형되고 비정상 거동이 난류경계층에서의 마찰저항 저감 기구와 밀접하게 관련된 것으로 관찰되었다. A POD analysis based on time-resolved PIV measurements in a circulating water channel has been conducted to identify the skin friction reduction mechanism of outer-layer vertical blades. A recent PIV measurement indicated 2.73% and 7.95% drag reduction in the blade plane and the blade-in-between plane, respectively. In the present study, the influence of vertical blades array upon the characteristics of the turbulent coherent structures was analyzed by the POD method. It is observed that the vortical structures are cut and deformed by the blades array and that their temporal evolution is strongly associated with the skin-friction drag reduction mechanism in the turbulent boundary layer flow.

POD 기법을 이용한 저 레이놀즈 수 충돌 제트의 비정상 거동 연구

안남현(Nam Hyun An),이인원(Inwon Lee) 한국가시화정보학회 2008 한국가시화정보학회지 Vol.6 No.1

적합직교분해(POD) 기법을 사용한 난류 응집구조 거동에 관한 연구

신성윤(Seong-Yun Shin),정광효(Kwang-Hyo Jung),강용덕(Yong-Duck Kang),서성부(Sung-Bu Suh),김진(Jin Kim),안남현(Nam-Hyun An) 대한조선학회 2017 대한조선학회 논문집 Vol.54 No.5

An experimental study in a recirculating water channel was carried out to investigate the effect of large coherent structures to the skin friction on a flat plate. Particle Image Velocimetry (PIV) technique was used to quantify characteristic features of coherent structures growing to the boundary layer. In the PIV measurement, it is difficult to calculate the friction velocity near the wall region due to laser deflection and uncertainty so that Clauser fitting method at the logarithmic region was adopted to compute the friction velocity and compared with the one directly measured by the dynamometer. With changing the free-stream velocity from 0.5 m/s to 1.0 m/s, the activity of coherent structures in the logarithmic region was increased over three times in terms of Reynolds stress. The flow field was separated by Variable Interval Time Averaging (VITA) technique into the weak and the strong structure case depending on the existence large coherent structures in order to validate its effectiveness. The stream-wise velocity fluctuation was scanned through at the boundary thickness whether it had a large deviation from background flow. With coherent structures connected from near-wall to the boundary layer, mean wall shear stress was higher than that of weak structure case. Proper Orthogonal Decomposition (POD) analysis was also applied to compare the energy budget between them at each free-stream velocity.

경계층 외부 수직날의 마찰저항 저감 기구에 대한 PIV 관측

박현(Hyun Park),안남현(Nam Hyun An),박성현(Seong Hyoen Park),전호환(Ho Hwan Chun),이인원(Inwon Lee) 한국가시화정보학회 2011 한국가시화정보학회지 Vol.9 No.1

외부경계층 수직 날 배열의 마찰저항 저감 효과

이인원(Inwon Lee),안남현(Nam Hyun An),전호환(Ho Hwan Chun) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

Various turbulent flow control stratergies are based on the disturbance as well as the attenuation of those regeneration mechanism of the coherent structures. Recently, up to 30% of the turbulent skin friction reduction has been reported by Hutchins and Choi (2002) by installing an array of vertical blades, which were subsequently named as outer-layer vertical blades. The drag-reducing efficiency of the outer-layer blades, however, was quantified only in terms of the reduction in the local skin friction coefficient, which was measured from the local velocity distribution. In the present study, a series of drag force measurements has been performed toward an assesment of the total drag reducing efficiency of the outer-layer vertical blades in towing tank and circulating water channel.

점탄성 재료의 복소수 동특성 측정방법

이인원(Inwon Lee),안남현(Nam Hyun An) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.5

A novel technique to measuret of viscoelastic properties of polymers is proposed to investigate complex Poisson’s ratio as a function of frequency. The forced vibration responses for the samples under the normal and the shear deformation are to be measured with varying load masses. The measured data were used to obtain the viscoelastic properties of the material based on an accurate 2D numerical deformation model of the sample. The 2D model enabled us to exclude data correction by the empirical form factor used in 1D model. Comprehensive measurements of viscoelastic properties of two slightly varied silicone RTV rubber (Silastic<SUP>®</SUP> S2) compositions were performed. Standard composition (90% PDMS polymer + 10% catalyst) and modified composition (92.5% polymer + 7.5% catalyst) were tested in temperature range from 30℃ to 70℃. Shear modulus, modulus of elasticity, loss factor, and both the real and the imaginary parts of the Poisson’s ratio were determined for frequencies from 50 to 400Hz in the linear deformation regime (at relative deformations 10<SUP>-4</SUP> ~10<SUP>-3</SUP>).

유연벽면 점탄성 소재 배합비와 저항저감 효과의 상관관계

이인원(Inwon Lee),안남현(Nam Hyun An) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.6

A specially designed flat plate was mounted vertically over the axial line in the wind tunnel of the Pusan National University. Strain balances were mounted in the trailing part of the plate to measure the skin friction drag over removable insertions of 0.55´0.25㎡ size. A set of the insertions was designed and manufactured: 3 ㎜ thick polished metal surface and three compliant surfaces. The compliant surfaces were manufactured of a silicone rubber Silastic<SUP>®</SUP> S2 (Dow Corning company). To modify the viscoelastic properties of the rubber, its composition was varied: 90% rubber + 10% catalyst (standard), 92.5% + 7.5% (weak), 85% + 15% (strong). Modulus of elasticity and the loss factor were measured accurately for these materials in the frequency range from 40 ㎐ to 3 ㎑. The aging of the materials (variation of their properties) for the period of one year was documented as well. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coating. The strong compliant coating achieved 5% drag reduction within a velocity range 20~40 m/s while standard and weak coatings increased drag reduction.

전역 최적화기법과 파라메트릭 변환함수를 이용한 선형 최적화

김희정(Hee-Jung Kim),전호환(Ho-Hwan Chun),안남현(Nam-Hyun An) 대한조선학회 2008 대한조선학회 논문집 Vol.45 No.6

This paper concerns the development of a designer friendly hull form parameterization and its coupling with advanced global optimization algorithms. As optimization algorithms, we choose the Partial Swarm Optimization(PSO) recently introduced to solve global optimization problems. Most general-purpose optimization softwares used in industrial applications use gradient-based algorithms, mainly due to their convergence properties and computational efficiency when a relatively few number of variables are considered. However, local optimizers have difficulties with local minima and non-connected feasible regions. Because of the increase of computer power and of the development of efficient Global Optimization (GO) methods, in recent years nongradient-based algorithms have attracted much attention. Furthermore, GO methods provide several advantages over local approaches. In the paper, the derivative-based SQP and the GO approach PSO are compared with their relative performances in solving some typical ship design optimization problem focusing on their effectiveness and efficiency.