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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Ocean System Engineering
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Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 1, Issue 4 - Dec 2011
Volume 1, Issue 3 - Sep 2011
Volume 1, Issue 2 - Jun 2011
Volume 1, Issue 1 - Mar 2011
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An In-situ Correction Method of Position Error for an Autonomous Underwater Vehicle Surveying the Sea Floor
Lee, Pan-Mook ; Jun, Bong-Huan ; Park, Jin-Yeong ; Shim, Hyung-Won ; Kim, Jae-Soo ; Jung, Hun-Sang ; Yoon, Ji-Young ;
International Journal of Ocean System Engineering, volume 1, issue 2, 2011, Pages 60~67
DOI : 10.5574/IJOSE.2011.1.2.060
This paper presents an in-situ correction method to compensate for the position error of an autonomous underwater vehicle (AUV) near the sea floor. AUVs generally have an inertial navigation system assisted with auxiliary navigational sensors. Since the inertial navigation system shows drift in position without the bottom reflection of a Doppler velocity log, external acoustic positioning systems, such as an ultra short baseline (USBL), are needed to set the position without surfacing the AUV. The main concept of the correction method is as follows: when the AUV arrives near the sea floor, the vehicle moves around horizontally in a circular mode, while the USBL transceiver installed on a surface vessel measures the AUV`s position. After acquiring one data set, a least-square curve fitting method is adopted to find the center of the AUV`s circular motion, which is transferred to the AUV via an acoustic telemetry modem (ATM). The proposed method is robust for the outlier of USBL, and it is independent of the time delay for the data transfer of the USBL position with the ATM. The proposed method also reduces the intrinsic position error of the USBL, and is applicable to the in-situ calibration as well as the initialization of the AUVs` position. Monte Carlo simulation was conducted to verify the effectiveness of the method.
Edge Line Information based Underwater Landmark for UUV
Yu, Son-Cheol ; Kang, Dong-Joung ; Kim, Jae-Soo ;
International Journal of Ocean System Engineering, volume 1, issue 2, 2011, Pages 68~75
DOI : 10.5574/IJOSE.2011.1.2.068
This paper addresses an underwater landmark for updating UUV positioning information. A method is proposed in which the landmark`s cubic shape and edge are recognized. The reliability, installation load, and management of landmark design were taken into consideration in order to assess practical applications of the landmark. Landmark recognition was based on topological features. The straight line recognition confirmed the landmark`s location and enabled an UUV to accurately estimated its underwater position with respect to the landmark. An efficient recognition method is proposed, which provides real-time processing with limited UUV computing power. An underwater experiment was conducted in order to evaluate the proposed method`s reliability and accuracy.
Hydroelastic Effects in Vibration of Plate and Ship Hull Structures Contacted with Fluid
Lee, Jong-Soo ; Song, Chang-Yong ;
International Journal of Ocean System Engineering, volume 1, issue 2, 2011, Pages 76~88
DOI : 10.5574/IJOSE.2011.1.2.076
The present study deals with the hydroelastic vibration analysis of structures in contact with fluid via coupled fluid-structure interaction (FSI) embedded with a finite element method (FEM) such that a structure displacement formulation is coupled with a fluid pressure-displacement formulation. For the preliminary study and validation of FEM based coupled FSI analysis, hydroelastic vibration characteristics of a rectangular plate in contact with fluid are first compared with the elastic vibration in terms of boundary condition and mode frequency. Numerical results from coupled FSI analysis have been shown to be rational and accurate, compared to energy method based theoretical solutions and experimental results. The effect of free surface on the vibration mode is numerically studied by changing the submerged depth of a rectangular plate. As a practical application, the hull structural vibration of 4,000 twenty-foot equivalent units (TEU) container ship is considered. Hydroelastic results of the ship hull structure are compared with those obtained from the elastic condition.
Terrain-Based Localization using Particle Filter for Underwater Navigation
Kim, Jin-Whan ; Kim, Tae-Yun ;
International Journal of Ocean System Engineering, volume 1, issue 2, 2011, Pages 89~94
DOI : 10.5574/IJOSE.2011.1.2.089
Underwater localization is a crucial capability for reliable operation of various types of underwater vehicles including submarines and underwater robots. However, sea water is almost impermeable to high-frequency electromagnetic waves, and thus absolute position fixes from Global Positioning System (GPS) are not available in the water. The use of acoustic telemetry systems such as Long Baseline (LBL) is a practical option for underwater localization. However, this telemetry network system needs to be pre-deployed and its availability cannot always be assumed. This study focuses on demonstrating the validity of terrain-based localization techniques in a GPS-denied underwater environment. Since terrain-based localization leads to a nonlinear estimation problem, nonlinear filtering methods are required to be employed. The extended Kalman filter (EKF) which is a widely used nonlinear filtering algorithm often shows limited performance under large initial uncertainty. The feasibility of using a particle filter is investigated, which can improve the performance and reliability of the terrain-based localization.
Effect of Cutout Orientation on Stress Concentration of Perforated Plates with Various Cutouts and Bluntness
Woo, Jin-Ho ; Na, Won-Bae ;
International Journal of Ocean System Engineering, volume 1, issue 2, 2011, Pages 95~101
DOI : 10.5574/IJOSE.2011.1.2.095
Perforated plates with cutouts (or holes) are widely used in structural members. These cutouts provide stress concentration in plates. Extensive studies have been carried out on stress concentration in perforated plates, which consider cutout shapes, boundary conditions, bluntness of cutouts, and more. This study presents stress concentration analyses of perforated plates with not only various cutouts and bluntness but also different cutout orientations. Especially, the effect of cutout orientation on stress concentration is emphasized since structural members have become more complicated recently. To obtain stress concentration patterns, a finite element program, ANSYS, is used. For the designated goal, three parameters are considered as follows: the shapes of polygonal cutouts (circle, triangle, and square), bluntness (a counter measure of radius ratio, r/R), and rotation of cutouts (
). From the analyses, it is shown that, in general, as bluntness increases, the stress concentration increases, regardless of the shape and rotation. A more important finding is that the stress concentration increases as the cutouts become more oriented from the baseline, which is the positive horizontal axis (+x). This fact demonstrates that the orientation is also a relatively significant design factor to reduce stress concentration. In detail, in the case of the triangle cutout, orienting one side of the triangle cutout to be perpendicular to the applied tensile forces is preferable. Similarly, in the case of the square cutout, it is more advantageous to orient two sides of square cutout to be perpendicular to the applied tensile force. Therefore, at the design stage, determining the direction of a major tensile force is required. Then, by aligning those polygon cutouts properly, we can reduce stress concentration.
Implementation of underwater precise navigation system for a remotely operated mine disposal vehicle
Kim, Ki-Hun ; Lee, Chong-Moo ; Choi, Hyun-Taek ; Lee, Pan-Mook ;
International Journal of Ocean System Engineering, volume 1, issue 2, 2011, Pages 102~109
DOI : 10.5574/IJOSE.2011.1.2.102
This paper describes the implementation of a precise underwater navigation solution using a multiple sensor fusion technique based on USBL, GPS, DVL and AHRS measurements for the operation of a remotely operated mine disposal vehicle (MDV). The estimation of accurate 6DOF positions and attitudes is the key factor in executing dangerous and complicated missions. To implement the precise underwater navigation, two strategies are chosen in this paper. Firstly, the sensor frame alignment to the body frame is conducted to enhance the performance of a standalone dead-reckoning algorithm. Secondly, absolute position data measured by USBL is fused to prevent cumulative integration error. The heading alignment error is identified by comparing the measured absolute positions with the DR algorithm results. The performance of the developed approach is evaluated with the experimental data acquired by MDV in the South-sea trial.
Numerical And Experimental Studies On Wing In Ground Effect
Suh, Sung-Bu ; Jung, Kwang-Hyo ; Chun, Ho-Hwan ;
International Journal of Ocean System Engineering, volume 1, issue 2, 2011, Pages 110~119
DOI : 10.5574/IJOSE.2011.1.2.110
Numerical and experimental studies were performed to investigate the aerodynamic performance of a thin wing in close vicinity to the ground. The vortex lattice method (VLM) was utilized to simulate the wing in ground (WIG) effect, which included freely deforming wake elements. The numerical results acquired through the VLM were compared to the experimental results. The experiment entailed varying the ground clearance using the DHMTU (Department of Hydromechanics of the Marine Technical University of Saint Petersburg) wing and the WIG craft model in the wind tunnel. The aero-dynamic influence of the design parameters, such as angles of attack, aspect ratios, taper ratios, and sweep angles were studied and compared between the numerical and experimental results associated with the WIG craft. Both numerical and experimental results suggested that the endplate augments the WIG effect for a small ground clearance. In addition, the vortex lattice method simulated the wake deformation following the wing in the influence of the ground effect.