• Title, Summary, Keyword: Underwater flexible structures

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Localization of AUV Using Visual Shape Information of Underwater Structures (수중 구조물 형상의 영상 정보를 이용한 수중로봇 위치인식 기법)

  • Jung, Jongdae;Choi, Suyoung;Choi, Hyun-Taek;Myung, Hyun
    • Journal of Ocean Engineering and Technology
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    • v.29 no.5
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    • pp.392-397
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    • 2015
  • An autonomous underwater vehicle (AUV) can perform flexible operations even in complex underwater environments because of its autonomy. Localization is one of the key components of this autonomous navigation. Because the inertial navigation system of an AUV suffers from drift, observing fixed objects in an inertial reference system can enhance the localization performance. In this paper, we propose a method of AUV localization using visual measurements of underwater structures. A camera measurement model that emulates the camera’s observations of underwater structures is designed in a particle filtering framework. Then, the particle weight is updated based on the extracted visual information of the underwater structures. The proposed method is validated based on the results of experiments performed in a structured basin environment.

Design and Simulation Tools for Moored Underwater Flexible Structures (계류된 수중 유연구조물의 설계 및 시뮬레이션 도구 개발)

  • Lee, Chun-Woo;Lee, Ji-Hoon;Choe, Moo-Youl;Lee, Gun-Ho
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.43 no.2
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    • pp.159-168
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    • 2010
  • This paper presents a mathematical model and simulation method for investigating the performance of set net systems and fish cage systems influenced by currents and waves. Both systems consist of netting, mooring ropes, a floating collar and sinkers. The netting and ropes were considered flexible structures and the floating collar was considered an elastic structure. Both were modeled on a mass-spring model. The structures were divided into finite elements and mass points were placed at the mid-point of each element, and the mass points were connected by mass-less springs. Each mass point was subjected to external and internal forces and the total force was calculated at every integration step. An implicit integration scheme was used to solve the nonlinear dynamic system. The computation method was applied to dynamic simulation of actual systems simultaneously influenced by currents and waves in order to evaluate their practicality. The simulation results improved our understanding of the behavior of the structure and provided valuable information concerning the optimized design of set net and fish cage systems exposed to an open ocean environment.

Development of Underwater Laser Scanner with Efficient and Flexible Installation for Unmanned Underwater Vehicle (무인잠수정을 위한 효과적이고 유연한 설치 성능을 지닌 수중 레이저스캐너 개발)

  • Lee, Yeongjun;Lee, Yoongeon;Chae, Junbo;Choi, Hyun-Taek;Yeu, Tae-Kyeong
    • Journal of Ocean Engineering and Technology
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    • v.32 no.6
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    • pp.511-517
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    • 2018
  • This paper proposes a vision-based underwater laser scanner with separate structures for an underwater camera and a line laser projector. Because the two devices can be adaptively placed regardless of the features of the unmanned underwater vehicle (UUV), the scanner has significant advantages in relation to its availability and flexibility. Position calibration between the underwater camera and laser projector guarantees a 3D measuring performance with high accuracy. To verify the proposed underwater laser scanner, a test-bed system was manufactured, which consisted of the laser projector, camera, Pan&Tilt, and Attitude and Heading Reference System (AHRS). A camera-laser calibration test and simple 3D reconstruction test were performed in a water tank and the experimental results are reported.

A Study on the engineering Properties of Repairing Epoxy-Mortar According to Hardener types for Structures under Underwater and Humidity (수중 및 습윤 환경구조물 보수용 에폭시 모르타르의 경화제 종류에 따른 공학적 특성에 관한 연구)

  • Park Duk Jun;Park Sang Hun;Lee Dae Kyung;Bae Kee Sun;Kim Jin Man;Back Sin Won
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.277-280
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    • 2005
  • Epoxy-mortar composites have been wildly used as finishing and repairing materials in the construction because of their excellent properties. Conventional epoxy-mortars and concretes have an inferior applicability and cost performance ratio due to the two component mixing of the epoxy resin and hardener. In this study, we examined the engineering effect of compressive strength and flexible strength according to the various epoxy-hardener in underwater and humidity environment, and evaluated the hardener types and physical effect of Epoxy mortar using cement binder in underwater and air condition. In this study, it was clarified that the engineering properties of repairing epoxy-motars were effected by the type of hardener.

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Material & Structural Characteristics of Composite Material Flexible Propeller (복합재료 유연 프로펠러의 재료 및 구조적 특성 연구)

  • Lee, Sang-Gab;Hwang, Jeong-Oh;Byun, Joon-Hyung
    • Journal of the Society of Naval Architects of Korea
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    • v.46 no.2
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    • pp.203-217
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    • 2009
  • The researches on the development of composite material propeller with outstanding damping effects have been actively attempted for the reduction of radiation noise of underwater vehicle propeller. Composite material suitable for the flexible propeller has the following advantages, such as high specific strength and specific stiffness, low thermal expansion coefficient, high resistance against environmental deterioration, low possibility of corrosion due to cavitation, nonoccurrence of rapid fracture due to fatigue, easy molding of complicated shape, easy repair maintenance and low production costs, etc. For the confirmation of optimal fiber array structures of composite material for the production of the flexible propeller blades, in this study, mechanical characteristics of its specimens according to materials were obtained and structural characteristics of propeller blade were also examined according to materials and stacking fiber arrays.

Analysis of Hydroelastic Response of a Pontoon-type Structure Considering Effect of Wave Breaker with Underwater Opening (해수순환 방파제를 고려한 폰툰형 구조물의 유탄성응답 해석)

  • 홍사영;최윤락;홍석원
    • Journal of the Society of Naval Architects of Korea
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    • v.40 no.5
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    • pp.53-59
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    • 2003
  • Ocean space utilization using VLFS(Very Large Floating Structures) can provide environmental impact free space by allowing sea water flow freely through the floating structure. Use of Pontoon type VLFS for that purpose needs employment of breakwaters for reduction of wave effects. Therefore, in order to maximize advantage of environmental impact free structure, the breakwater should be the one that can allow water flow freely through it, too. In this paper hydroelastic response of a pontoon type structure is analyzed considering breakwaters which allow water flow through its opening at bottom of the breakwaters. Mode superposition technique is used for solving equation of flexible body while interactions between the pontoon and breakwaters is considered based on generalized mode concept. Bi-quadratic nine node higher-order boundary element method is adopted for more accurate numerical treatment near sharp edged body shape. Performance of various combinations of breakwaters is investigated.

Dynamic behavior of a submersible fish cage rigged with a circular floating and a sinking collar (상하가 원형 파이프로 구성된 부침식 가두리의 동적 거동 해석)

  • Lee, Chun-Woo;Lee, Ji-Hoon;Choe, Moo-Youl;Lee, Gun-Ho
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.46 no.1
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    • pp.20-31
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    • 2010
  • In this research, the submersible fish cage was designed to avoid structural and biological damage during harsh sea conditions. The submersible cage system consists of netting, mooring ropes, a floating collar, floats, sinkers and anchors. Whole elements of the cage were modeled on the mass-spring model. The computer simulations were carried out to investigate the dynamic behavior of the cage and to calculate mooring line tension subjected to tidal currents and waves. As expected, the tension values in the mooring line of the submerged position are 36% less compared to that of the surface cage under the same loading conditions. As the wave was used in combination with the current velocity of 1m/s, the average tensile load for the submerged cage showed 85% of the value for the floating cage. The simulation results provide an improved understanding of the behaviors of the structure and valuable information on the optimized design of the cage system exposed to open ocean environmental factors.