• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.335-338
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• 2006

The more deeply the researches make progress in ocean researches including the seabed resource investigation or the oceanic ecosystem investigation, the more important the role of UUV gets. In case of study on the deep sea, there are difficulties in telecommunications between AUV and ships, and in data communication and recharging. Therefore, docking is required. In AUV docking system, the AUV should identify the position of docking and make contact with a certain point of docking device. MOERI (Maritime & Ocean Engineering Research Institute), KORDI has conducted the docking testing on AUV ISIMI in KORDI Ocean Engineering Water Tank. As AUV ISIMI approachs the docking device, it is presented that attitude is unstable, because the lights Which is on Image Frame are disappeared. So we fix the rudder and stem, if the lights on Image Frame are reaching the specific area in the Image Frame. In this paper, we intend to solve the problems that were found in the testing, which, first, will be identified via simulation.

• 한국해양공학회지
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• 제26권3호
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• pp.6-12
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• 2012

In this paper, addressed is the control problem of generating a formation for a group of unmanned surface and underwater vehicles. The formation control scheme proposed in this work is based on a fusion of theleader-follower and virtual reference approaches. This scheme gives a formation constraint representation that is independent of the number of vehicles in the formation and the resulting control algorithm is scalable. One of the most important features in controller design is the ability of the controller to globally and exponentially stabilize the formation errors defined by the formation constraints. The proposed controller is based on feedback linearization, and the formation errors are shown to be globally and exponentially stable in the sense of Lyapunov.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.204-209
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• 2004

It is well known fact that acoustic positioning systems are absolutely needed for various underwater operations. According to the distances between their sensors they are classified into three parts: long baseline(LBL), short baseline(SBL), and ultra-short baseline(USBL). Among them the USBL system is widely used because of its simplicity, although it is the most inaccurate. Recently, in order to increase the positioning accuracy, various USBL systems using broadband signal such as MFSK(Multiple Frequency Shift Keying) are produced. However, their positioning accuracy is still limited by background noise and reflected waves. Therefore, there is difficulty in applying the USBL system using MFSK signal in a shallow water with noisy conditions. In order to examine the effect of the noise and wave reflections this paper analyze position errors for various conditions using numerical simulations. The simulation results say that tile SNR must be greater than 20dB and errors in the vertical direction are slightly increased by wave reflections by upper and lower boundaries.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.249-256
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• 2004

KRISO/KORDI is currently developing a deep-sea unmanned underwater vehicle (UUV) system which is composed of a launcher, an ROV, and an AUV. Two USBL acoustic positioning systems will be used for UUV's navigation. One is for the deep sea positioning of all three vehicles and the other is for AUV's guidance to the docking device on the launcher. In order to increase the position accuracy MFSK(Multiple Frequency Shift Keying) broadband signal will be used. As the first step to the implementation of a USBL system, this paper studies USBL positioning algorithm using MFSK signals. Firstly, the characteristics of MFSK signal is described with various MFSK parameters: number of frequencies, frequency step, center frequency, and pulse length. Time and phase delays between two received signals are estimated by using cross-correlation and cross-spectrum methods. Finally an USBL positioning algorithm is derived by converting the delays to difference of distances and applying trigonometry. The simulation results show that the position accuracy is improved highly when both cross-correlation and cross-spectrum of MFSK signals are used simultaneously.

• 한국해양공학회지
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• 제24권4호
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• pp.23-31
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• 2010

The flow around a remotely-operated vehicle (ROV) has been investigated numerically to improve the resistant performance by modifying the hull form of the ROV. In the case of the base hull form considered in this study, form drag rather than friction drag was the dominant component of total drag. Subsequently, the surfaces that were most susceptible to local pressure effects were modified to give them a more streamlined shape. Eleven different hull forms were chosen to undergo surface modification for drag reduction. In addition, four different boat-tail appendages with different slant angles were installed at the stern to reduce the wake vortices that are induced by the local regions of very low pressure. Consequently, a total of 11 different hull forms for drag reduction were considered. The final hull form, which combined the hull for which surface modification resulted in the lowest drag with a boat-tail appendage with a 15-degree slant angle, resulted in a drag reduction of 20%.

• 한국전산유체공학회지
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• 제21권1호
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• pp.78-85
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• 2016

While most AUV researches have concerned about single hydrofoil, practical AUV's are generally operated with multiple hydrofoils. Double hydrofoil study attempts to evaluate thrust and efficiency with various flapping motions, and carries out design optimization using parametric analysis. Flow patterns such as vortex shedding and wake-body interaction are carefully investigated during design variable sensitivity analysis. The purpose of this design optimization is to find out the optimal motion that yields maximum thrust and efficiency. The design optimization employes several techniques such as table of orthogonal arrays, Kriging method, ANOVA analysis and MGA. Throughout this research, it is possible to find the optimal values of heaving ratio, heaving shift and pitch shift: Heaving ratio 0.950, heaving shift $23.120^{\circ}$ and pitch shift $89.991^{\circ}$ are found to be optimal values in double hydrofoil motions. Thrust and efficiency are 16.7% and 35.1% higher than existing AUV that did not consider nonlinear dependency of motion parameters. This results may offer an effective framework that is applicable to various AUV motion analyses and designs.

• 대한공업교육학회지
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• 제34권1호
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• pp.238-251
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• 2009

배열센서에 영향을 주는 자체소음은 그 시스템이 설치된 곳에서 발생하는 소음과 해양으로부터 들어오는 주변소음을 포함한 소음으로 정의된다. 수중에서의 탐지를 위한 배열 구조는 표면을 따라 발생되는 유체 유기소음에 많은 영향을 받는다. 본 논문에서는 곡면배열 음향 센서를 설계하기 위하여 유동유기 소음의 영향으로 인한 주파수 밀도 함수의 적분식의 주요 구성요소인 전달함수(transfer function)를 저파수 영역에서 수치해석 하였다. 난류 경계층에서 발생하는 유입 소음은 수정된 Corcos 모델을 이용하였다. 저파수 영역에서의 전달함수의 특성은 고정판의 두께와 밀도가 작아질수록 함수의 적분값은 적어지므로 소음의 영향은 줄어드는 것으로 나타났다. 또한 Corcos 벽면 압력과 전달함수의 곱에 따른 특성과 주파수 밀도 함수의 곱의 변화를 보였다. 향후 이러한 연구는 무인 잠수정에 탑재할 수 있는 곡면배열 센서의 설계에 응용이 가능하리라 판단된다.

• 지구물리와물리탐사
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• 제27권1호
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• pp.57-68
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• 2024

온실가스 저감을 위하여 대규모의 단지를 건설할 수 있고 발전 효율성이 우수한 해상 풍력이 각광 받고 있다. 해상 풍력 단지에서 생산한 전력을 송전하기 위해서는 해저 전력 케이블이 필수적이며, 케이블의 모니터링 및 고장 지점 파악을 위하여 해저 케이블의 위치 또는 매설 심도 분석이 필요하다. 본 논문에서는 해저 전력 케이블을 탐지하기 위한 기술 및 연구에 대하여 소개하였으며, 탄성파/음향, 전자 탐사, 자력 탐사로 분류하여 조사하였다. 탄성파/음향은 주로 선박에 장비를 설치하여 해저 전력 케이블을 탐지하였으며, 전자 및 자력 탐사는 AUV, ROV와 같은 무인 잠수정에 장비를 설치하여 케이블을 탐지하였다. 본 논문을 활용한다면 해저 케이블 탐지 기술에 대한 기초자료로 사용될 수 있을 것으로 생각된다.

• 지구물리와물리탐사
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• 제14권1호
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• pp.80-87
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• 2011

자율무인잠수정은 해수면탐사선에 비해 해저면에 더 가까이 접근할 수 있는 장점을 제공한다. 수심자료, 해저면 물질 정보와 해저면 하부 영상을 얻기 위해서는 자율무인잠수정에 탑재된 다중빔음향즉심기, 해저면영상탐사기 및 천부지층탐사기 등이 유용하게 사용된다. 일본해양연구개발기구는 3000m급 자율무인잠수정 우라시마를 개발하였다. 잠수정의 전력공급용 연료전지시스템의 공학적 개발과 시험과정을 거쳐 우라시마에는 신형 리튬이온전지 시스템이 설치되었다. 잠수정은 초기 공학적인 업무에서 과학적 사용 목적으로 개량되었다. 다양한 과학장비들이 추가되었고 2006년부터 과학적인 목적의 임무수행을 위한 잠항시험이 수행되었다. 2007년 시험운항에서 일본 기이반도 해역 북구마노분지 부근에서 우라시마의 해저면영상탐사기와 천부지층탐사기를 이용하여 고해상 음향영상자료를 획득하였다. 후방산란강도 도면에서는 많은 암설류가 확인되었고, 천부지층탐사단면에서 연구해역의 북동쪽 끝 부근의 하부구조가 확인되었다. 이러한 특징은 최신 선상지의 형성과 관련된 구조를 암시한다. 그러나 남서 해역에서는 해저면 하부 ~20 ms 부근에서 강한 반사층이 존재하는데, 이는 삭박특징으로 해석되며 현재는 더 젊은 해저 퇴적물로 덮여있다. 잠수정의 성능은 지속적으로 향상되고, 우라시마를 활용하여 많은 유용한 결과가 얻어질 것으로 기대된다.

• 제어로봇시스템학회논문지
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• 제8권12호
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• pp.1023-1030
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• 2002

Since the dynamics of autonomous underwater vehicles (AUVs) are highly nonlinear and their hydrodynamic coefficients vary with different vehicle's operating conditions, high performance control systems of AUVs are needed to have the capacities of teaming and adapting to the variations of the vehicle's dynamics. In this paper, a linearly parameterized neural network (LPNN) is used to approximate the uncertainties of the vehicle dynamics, where the basis function vector of the network is constructed according to the vehicle's physical properties. The network's reconstruction errors and the disturbances in the vehicle dynamics are assumed be bounded although the bound may be unknown. To attenuate this unknown bounded uncertainty, a certain estimation scheme for this unknown bound is introduced combined with a sliding mode scheme. The proposed controller is proven to guarantee that all signals in the closed-loop system are uniformly ultimately bounded (UUB). Numerical simulation studies are performed to illustrate the effectiveness of the proposed control scheme.