• Journal of Electrical Engineering and Technology
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• 제7권6호
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• pp.1023-1033
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• 2012

An underwater planar covering problem is studied where the coverage region consists of polygonal cells, and line sweep motion is used for coverage. In many subsea applications, sidescan sonar has become a common tool, and the sidescan sonar data is meaningful only when the sonar is moving in a straight line. This work studies the optimal line sweep coverage where the sweep paths of the cells consist of straight lines and no turn is allowed inside the cell. An optimal line sweep coverage solution is presented when the line sweep path is parallel to an edge of the cell boundary. The total time to complete the coverage task is minimized. A unique contribution of this work is that the optimal sequence of cell visits is computed in addition to the optimal line sweep paths and the optimal cell decomposition.

• 수산해양기술연구
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• 제53권1호
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• pp.19-40
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• 2017

A scientific and objective sound exposure criterion for underwater sound damage on fish has been required since there has been many disputes between an underwater sound maker and a fish damage receiver. The existing criteria are still incomplete scientifically owing to a degree of variability of underwater sounds, diversity of fish hearing sensitivity and damage types, etc. This study reviews existing studies on a hearing mechanism of fish species, manmade underwater sound characteristics and sound exposure assessment parameters, and recent sound exposure criteria. A governing equation for damage coverage estimation and damage coverage dependency on sound source level, ambient noise and transmission loss are also reviewed and interpreted based on sound exposure environments. The foreign and Korean (National Environmental Dispute Medication Commission) criteria are reviewed and compared based on scientific aspects. In addition, the deficit and limit of Korean criteria are presented. The objective of this study is to give a direction for related researches and legislation of sound exposure criteria on fish.

• 해양환경안전학회지
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• 제28권3호
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• pp.441-450
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• 2022

The introduction of autonomous underwater gliders (AUGs) specifically addresses the reduction of operational costs that were previously prohibited with conventional autonomous underwater vehicles (AUVs) using a "scaling-down" design philosophy by utilizing the characteristics of autonomous drifters to far extend operation duration and coverage. Long-duration, wide-area missions raise the cost and complexity of in-water testing for novel approaches to autonomous mission planning. As a result, a simulator that supports the rapid design, development, and testing of autonomy solutions across a wide range using software-in-the-loop simulation at faster-than-real-time speeds becomes critical. This paper describes a faster-than-real-time AUG simulator that can support high-resolution bathymetry for a wide variety of ocean environments, including ocean currents, various sensors, and vehicle dynamics. On top of the de facto standard ROS-Gazebo framework and open-sourced underwater vehicle simulation packages, features specific to AUGs for ocean mapping are developed. For vehicle dynamics, the next-generation hybrid autonomous underwater gliders (Hybrid-AUGs) operate with both the buoyancy engine and the thrusters to improve navigation for bathymetry mappings, e.g., line trajectory, are is implemented since because it can also describe conventional AUGs without the thrusters. The simulation results are validated with experiments while operating at 120 times faster than the real-time.

• 융합신호처리학회논문지
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• 제21권2호
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• pp.92-100
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• 2020

현재 수중 촬영을 통해 물속이나 바다 속을 촬영하려는 수요는 매우 빠르게 늘어나고 있다. 방송용 수중 촬영, 레저 및 스포츠용, 군사 및 작전용 등 그 적용 범위 또한 빠르게 늘어나고 있다. 그중 특별히 우리는 선박 선저에 부착된 해양 생물들을 촬영하고 검사하기 위해 수중 드론에 사용 될 최적의 카메라를 선정한다. 3대의 카메라들을 성능적으로 비교하는데 수중 촬영이라는 특별한 상황에서 객관적 기준, 주관적 기준을 사용하여 비교 및 평가한다. 본 연구는 수중 촬영이라는 특이한 상황에서 카메라의 해상도와 같은 성능적 기준이 객관적 기준과 주관적 기준에도 부합하는지를 확인한다. 그리고 훌륭한 화질 제공에는 영상을 보정하는 필터 외에도 적절한 카메라 선정이 중요하다는 점을 보여준다. 이 연구 후에도 좀 더 다양한 카메라들을 이용한 연구를 통해서 수중 촬영용 카메라 화질 비교의 적절한 기준을 제시해 줄 수 있을 것이다.

• 전자공학회논문지
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• 제54권4호
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• pp.3-9
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• 2017

수중환경에서는 전력 공급이 어렵기 때문에 통신 프로토콜 설계에 있어서 전력 효율은 중요한 고려사항들 중 하나이다. 본 논문에서는 UUV(Unmanned Underwater Vehicle)와 AUV(Autonomous Underwater Vehicle) 같은 이동 노드를 갖는 수중통신망에 대해 에너지 효율적인 매체접속제어(MAC : Medium Access Control) 프로토콜을 연구하였다. 이동 노드간의 통신에서는 데이터 교환 중에 노드 이동으로 인해 서로의 전파 반경을 벗어나 전송 중인 데이터를 완료하지 못하고 에너지만 낭비하는 경우가 발생할 수 있다. 특히, 수중 통신 채널 환경에서는 지상보다 약 $10^5$ 배의 느린 전파 지연을 가지므로 데이터의 전송 완료 전에 서로의 전파 반경을 벗어날 확률이 지상보다 커서 이로 인한 에너지 낭비가 더 많게 된다. 제안한 mobility-MAC 프로토콜은 수신노드의 위치와 노드의 이동 속도를 고려하여 Dropping Zone을 정의하고 데이터 전송 시도를 제어한다. 데이터 전송시도는 Dropping Zone에서 무조건 데이터 전송을 드롭(drop)을 하는 것이 아니라, 데이터 전송 중 노드가 전파 반경을 이탈할 확률을 예측하여 드롭하는 방법이다. 결과적으로, 조건적 드롭을 통해 잘못된 드롭을 감소시켜 전송지연과 통신수율의 향상을 가져왔고 유효한 데이터 드롭으로 에너지 낭비를 방지하여 에너지 효율도 증가되었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.817-832
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• 2021

In this paper, a simple practical method to estimate the drag of Super-Cavitating Underwater Vehicles (SCUV) is proposed that can obtain the drag with only principal dimensions in an initial design stage. SCUV is divided into cavitator, forebody, afterbody, base, and control fin and the drag of each part is estimated. The formulas for the drag coefficient are proposed for the disk and cone type cavitators and wedges used as control fins. The formulas are a function of cavitation number, cone or wedge angle, and Reynolds number. This method can confirm the drag characteristics of SCUV that the drag hump appears according to the coverage of the body by the cavity and the cavitator drag remains only when the entire body is covered by cavity. Applying this method to SCUV of various shapes, it is confirmed that the effects of cavitating and non-cavitating conditions, cavitator and body shape, and speed could be found.

• 한국멀티미디어학회논문지
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• 제13권11호
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• pp.1657-1666
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• 2010

수중 센서 네트워크(UWSN: Underwater Wireless Sensor Networks)는 수중 센서 노드들의 에너지 자원의 제약이 심하고, 제한된 통신 대역폭과 다양한 전파지연 등의 환경적인 특성 때문에 효율적이고 안정적인 데이터전송 방법이 요구된다. 본 논문에서는 수중 센서 네트워크의 센서 노드들이 해양 바닥에 고정된 2차원 구조(2D: two-dimensional underwater wireless sensor network model)에서 이상적인 셀 크기의 육각 모자이크 구조를 이용한 향상된 하이브리드 전송 방법을 설명하고, 또한 센서 노드를 해양 바닥의 닻에 매달아 움직임이 가능한 3차원 구조(3D: three-dimensional underwater wireless sensor network model)에서 효과적인 데이터전송을 위한 에너지 효율적인 인식 및 통신범위를 확장하는 방법을 제안한다. 2D 및 3D 구조에서 제안된 방법들은 시뮬레이션 결과에 의해 기존의 전송 방법보다 높은 에너지 효율성을 가지는 것이 확인되었다.

• 전기학회논문지
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• 제65권1호
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• pp.135-141
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• 2016

Recently, the needs for the development and application of marine robots are increasing as marine accidents occur frequently. However, it is very difficult to acquire the information by utilizing marine robots in the marine environment. Therefore, the needs for the researches of sensor networks which are composed of underwater, surface and aerial robots are increasing in order to acquire the information effectively as the information from heterogeneous robots has less limitation in terms of coverage and connectivity. Although various researches of the sensor network which is based on marine robots have been executed, all of the underwater, surface and aerial robots have not yet been considered in the sensor network. To solve this problem, a collaborative control method based on the acoustic information and image by the sonars of the underwater robot, the acoustic information by the sonar of the surface robot and the optical image by the camera of the static-floating aerial robot is proposed. To verify the performance of the proposed method, the collaborative control of a MUR(Micro Underwater Robot) with an OAS(Obstacle Avoidance Sonar) and a SSS(Side Scan Sonar), a MSR(Micro Surface Robot) with an OAS and a BMAR(Balloon-based Micro Aerial Robot) with a camera are executed. The test results show the possibility of real applications and the need for additional studies.

• 산업경영시스템학회지
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• 제37권2호
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• pp.62-69
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• 2014

The capability and cost effectiveness of UUV and USV bring to underwater survey, target detection and identification operations have been widely demonstrated and accepted in recent years. Future USV systems may deploy UUVs to gain the advantage of higher area coverage rates through multiple and simultaneous operations. In this paper, we present an architecture of USV and UUV for mine countermeasure with results of measures on effectiveness.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.63-64
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• 2007

The Underwater Wireless Sensor Networks (UWSN) consists of sensor nodes equipped with limited sensing coverages, energy resources and communication capacity. Hence, the deployment and movement algorithm is a key issue that needs to be organized in order to improve the sensing efficiency of the networks. In this paper, we use a Queen problem and Knapsack problem to prevent the reiteration phenomenon of sensors, to guarantee improvement sensing coverage and efficiency in the 3D UWSN.