• Ocean Systems Engineering
• /
• v.9 no.4
• /
• pp.391-407
• /
• 2019

Tracking the location (position) of a surface or underwater marine vehicle is important as part of guidance and navigation. While the Global Positioning System (GPS) works well in an open sea environment but its use is limited whenever testing scaled-down models of such vehicles in the laboratory environment. This paper presents the design, development and implementation of a low energy ultrasonic augmented single beacon-based localization technique suitable for such requirements. The strategy consists of applying Extended Kalman Filter (EKF) to achieve location tracking from basic dynamic distance measurements of the moving model from a fixed beacon, while on-board motion sensor measures heading angle and velocity. Iterative application of the Extended Kalman Filter yields x and y co-ordinate positions of the moving model. Tests performed on a free-running ship model in a wave basin facility of dimension 30 m by 30 m by 3 m water depth validate the proposed model. The test results show quick convergence with an error of few centimeters in the estimated position of the ship model. The proposed technique has application in the real field scenario by replacing the ultrasonic sensor with industrial grade long range acoustic modem. As compared with the existing systems such as LBL, SBL, USBL and others localization techniques, the proposed technique can save deployment cost and also cut the cost on number of acoustic modems involved.

• The Journal of Korea Robotics Society
• /
• v.10 no.1
• /
• pp.1-8
• /
• 2015

This paper proposes a study for accurate surface localization system using DWT(Discrete Wavelet Transform) and GPS/INS fusion algorithm. Because the propagation in the underwater is not passed by characteristics of the medium unlike the ground, the sonar system like DVL is used instead of GPS. But since these systems are installed on the seafloor and operated, a long time is required for installation and navigation systems are limited outside of the range area. And it is difficult to estimate position in a three-dimensional considering the depth in actual marine environment. In this paper, before the development of underwater localization system, precisely estimated position system is proposed in a two-dimensional by developing surface localization system using removing noise and disturbance with DWT and relatively inexpensive GPS and INS sensor.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.1
• /
• pp.54-59
• /
• 2009

In this paper, the effect of the position and size of a lumped mass on the structural stability of a high speed underwater vehicle is presented. For simplicity, a real vehicle was modeled as a follower force subjected beam that was resting on an elastic foundation, and the lumped mass effect was simplified as an elastic intermediate support. The stability of the simplified model was numerically analyzed based on the Finite element method (FEM). This numerical simulation revealed that flutter type instability or divergence type instability occurs, depending on the position and stiffness of the elastic intermediate support, which implies that the instability of the real model is affected by the position and size of the lumped mass.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.1
• /
• pp.40-46
• /
• 2018

In order to successfully detect and identify underwater targets located on the seabed, unmanned surface vehicles (USVs) typically acquire acoustic signals with a side-scan sonar device and reconstruct information about the target from the processed images. As the quality of the side-scan sonar images acquired by USVs depends on the environment and operating parameters, using modeling and simulation techniques to design side-scan sonar devices can help optimize the reconstruction of the sonar images. In this work, we study a side-scan sonar design for use in USVs, that takes the movement of the platform into account. First, we constructed a simulated seabed environment with underwater targets, and specified the maneuvering conditions and sonar systems. We then generated the acoustic signals from the simulated environment using the sonar equation. Finally, we successfully imaged the simulated seabed environment using simple signal processing. Our results can be used to derive USV side-scan sonar design parameters, predict the resulting sonar images in various conditions, and as a basis for determining the optimal sonar parameters of the system.

• Journal of the Society of Naval Architects of Korea
• /
• v.45 no.6
• /
• pp.579-589
• /
• 2008

In the past few years, there are many studies and researches of the underwater vehicles which are carried out its mission using sonar sensors. MSCL(Marine System Control Lab.) at Inha University developed test-bed small ROV, ISRO. ISRO is an open-frame type and has 4 thrusters. ISRO can control 4 motions i.e surge, sway, yaw and heave with sonar sensors. ISRO is developed for inspection of ship hull, marine structure, plant of lake or river and so on. When ROV ISRO inspects something, it is necessary to control the position of ROV ISRO's for the movement and anti-collision with structures in the underwater. In this paper, we deal with the development of a small ROV and verification of the position control system via simulation and experiment using sonar sensors.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.05a
• /
• pp.443-449
• /
• 2010

Recently underwater systems moving at hyper-speed such as a super-cavitating torpedo have been studied for their practical advantage of the dramatic drag reduction. In this study we are focusing our attention on super-cavitating flows around axisymmetric cavitators. A numerical method based on inviscid flow is developed and the results for several shapes of the cavitator are presented. First using a potential based boundary element method, we find the shape of the cavitator yielding a sufficiently large enough cavity to surround the body. Second, numerical predictions of super-cavity are validated by comparing with experimental observations carried out in a high speed cavitation tunnel at Chungnam National University (CNU CT).

• International Journal of Ocean System Engineering
• /
• v.3 no.2
• /
• pp.50-60
• /
• 2013

This paper presents a novel approach to the design of an adaptive fuzzy sliding mode controller for depth control of an autonomous underwater vehicle (AUV). So far, AUV's dynamics are highly nonlinear and the hydrodynamic coefficients of the vehicles are difficult to estimate, because of the variations of these coefficients with different operating conditions. These kinds of difficulties cause modeling inaccuracies of AUV's dynamics. Hence, we propose an adaptive fuzzy sliding mode control with novel fuzzy adaptation technique for regulating vertical positioning in presence of parametric uncertainty and disturbances. In this approach, two fuzzy approximator are employed in such a way that slope of the linear sliding surface is updated by first fuzzy approximator, to shape tracking error dynamics in the sliding regime, while second fuzzy approximator change the supports of the output fuzzy membership function in the defuzzification inference module of fuzzy sliding mode control (FSMC) algorithm. Simulation results shows that, the reaching time and tracking error in the approaching phase can be significantly reduced with chattering problem can also be eliminated. The effectiveness of proposed control strategy and its advantages are indicated in comparison with conventional sliding mode control FSMC technique.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.7
• /
• pp.1202-1208
• /
• 2008

This paper represents the multiple sensor fusion algorithm for the deep-sea unmanned underwater vehicles (UUV), composed of a remotely operated vehicle (ROV) 'Hemire' and a depressor 'Henuvy'. The performance of underwater positioning system usually highly depend on that of acoustic sensors such as ultra short base line(USBL), long base line(LBL) and altimeter. A practical sensor fusion algorithm is proposed in the sense of a moving window concept. The performance of the proposed algorithm can be observed by applying the algorithm to the Hemire sea trial data which was measured at the East Sea.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.12 no.1
• /
• pp.832-842
• /
• 2020

The coordination control of multiple Underactuated Underwater Vehicles (UUVs) moving in three dimensional space is investigated in this paper. The coordinated path following control task is decomposed into two sub tasks, that is, path following control and coordination control. In the spatial curve path following control task, path following error dynamics is build in the Serret-Frenet coordinate frame. The virtual reference object can be chosen freely on the desired spatial path. Considering the speed of the UUV, the line-of-sight navigation is introduced to help the path following errors quickly converge to zero. In the coordination control sub task, the communication topology of multiple UUVs is described by the graph theory. The speed of each UUV is adjusted to achieve the coordination. The path following system and the coordination control system are viewed as the feedback connection system. Input-to-state stable of the coordinated path following system can be proved by small gain theorem. The simulation experiments can further demonstrate the good performance of the control method.

• Tribology and Lubricants
• /
• v.38 no.6
• /
• pp.287-290
• /
• 2022

Compressed-water-type launching devices convert the force from compressed water into force-launching underwater structures, such as torpedos and autonomous underwater vehicles. In particular, the overpressure wave in the launching tube is a critical design factor for the launching device. This paper presents a simplified formula for simulating overpressure waves in the launching tube of a compressed-water-type launching device. Scaled model experiments were performed to obtain actual measurement data of overpressure waves in a launching tube with varying piston speeds to examine the practical applicability of the simplified formula. The main factor of the simplified formula was estimated using an optimization technique. The time history of the overpressure waves was satisfactorily simulated using the estimated factor values and showed consistency with the measurement data. In addition, the trend of change by the piston speed of the estimated factors was reviewed, and the practical applicability was demonstrated. A systematic study of the factors influencing the overpressure waves in launching tubes will be possible using experimental data for more various conditions and the proposed simplified formula.