• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.6
• /
• pp.322-330
• /
• 2020

This study deals with underwater explosion (UNDEX) characteristics of various non-explosive underwater shock sources for the development of non-explosive underwater shock testing devices. UNDEX can neutralize ships' structure and the equipment onboard causing serious damage to combat and survivability. The shock proof performance of naval ships has been for a long time studied through simulations, but full-scale Live Fire Test and Evaluation (LFT&E) using real explosives have been limited due to the high risk and cost. For this reason, many researches have been tried to develop full scale ship shock tests without using actual explosives. In this study, experiments were conducted to find the characteristics of the underwater shock waves from actual explosive and non-explosive shock sources such as the airbag inflators and Vaporizing Foil Actuator (VFA). In order to derive the empirical equation for the maximum pressure value of the underwater shock wave generated by the non-explosive impact source, repeated experiments were conducted according to the number and distance. In addition, a Shock Response Spectrum (SRS) technique, which is a frequency-based function, was used to compare the response of floating bodies generated by underwater shock waves from each explosion source. In order to compare the magnitude of the underwater shock waves generated by each explosion source, Keel Shock Factor (KSF), which is a measure for estimating the amount of shock experienced by a naval ship from an underwater explosionan, was used.

• Journal of Ocean Engineering and Technology
• /
• v.30 no.2
• /
• pp.141-149
• /
• 2016

In this technical note, the issues and challenges for the launch and recovery systems (LARS) and related techniques for the operation of an underwater robot from a manned platform are considered. Various types of LARS fitted to specific manned platforms, surface or sub-surface, are surveyed and categorized. The current UUV launch and recovery systems from surface ships and submarines utilize time consuming processes. As underwater robot technologies evolve and their roles are defined, safe and effective launch and recovery methods should be developed capable of reliable and efficient operations, particularly at a high sea state. To improve the existing underwater robot capabilities, LARS technology maturation is required in the near term, leading to the ability to incorporate autonomous LARS for an underwater robot on a manned platform. In the near term, particular emphasis should be placed on UUV LARS, which are surface ship based, with submarine based systems in the long term. Furthermore, for a dedicated LARS ship, independent of the existing host ship type, particular emphasis should be given to fully utilizing the capabilities of underwater robots.

• Journal of Institute of Control, Robotics and Systems
• /
• v.19 no.8
• /
• pp.688-693
• /
• 2013

This paper proposes a new method on attitude control of an underwater robot by using five ABTs (Attitude Ballast Tank). A pipe is connected to the bottom of the ABTs and transfers water by a pump, while another pipe is connected to the top of the ABT to transfer air. The buoyancy center of the underwater robot can be changed by means of the water transfer. This way, the attitude of the underwater robot can be maintained and/or controlled as desired. The changes of the center of gravity and the buoyancy central are estimated by a Lagrangian function which is similar to that for an inverted pendulum. The controller in this paper is designed by modeling of the underwater robot and selecting suitable gains of a PD controller which has fast response characteristics. This paper shows the possibility of the attitude control of an underwater robot by changing the center of gravity and the buoyancy center of the robot. Moreover, experimental results verify that the controller is effective in maintaining Roll/Pitch of the underwater robot with very low power consumption.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.1
• /
• pp.1-8
• /
• 2010

Recently, the demand of landscape lighting for underwater dam is rapidly increased by expansion of hydrophilic space. But it occurred the problems such as weakness of safety and display effect of underwater dam lighting lamp currently in use. Therefore, for solving these problems and improving underwater dam lighting lamp, this paper is focused on safety, energy saving, display flexibility of underwater dam lighting lamp and analyzed the related deriving problems by research on the actual condition. As a result, it presents a developed LED mold type underwater light instead of underwater dam lighting lamp. By the results of this research, it is considered that practical use of underwater dam lighting is very useful in waterside space for dams, water fountain, swimming pool, and etc. Moreover, it can be extended/applied in various ways.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.2
• /
• pp.217-224
• /
• 2017

This study proposes an evaluation method for time delay function(TDF) of Point Detonation(PD) fuse using underwater explosion and water entry phenomena. Until now, nothing but the naked eyes of an observer or video images have been used to determine whether the TDF of PD fuze is operated or not. The observer has verified the performance of TDF by analysing the shape of the plume formed by underwater explosion. However, it is very difficult to evaluate the TDF of PD fuse by these conventional methods. In order to overcome this issue, we propose a method using underwater sound signal emitted from the underwater explosion of high explosive charge. The result shows that the measured sound signal is in accord with the physical phenomena of water entry of warhead as well as underwater explosion. Also, from the hypothesis test of bubble period, difference on underwater sound analysis between dud event and delay one is proved.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.3
• /
• pp.243-251
• /
• 2016

Autonomous Underwater Vehicles (AUVs) generally work in complex marine environments. Any fault in AUVs may cause significant losses. Thus, system reliability and automatic fault diagnosis are important. To address the actuator failure of AUVs, a fault diagnosis method based on the Gaussian particle filter is proposed in this study. Six free-space motion equation mathematical models are established in accordance with the actuator configuration of AUVs. The value of the control (moment) loss parameter is adopted on the basis of these models to represent underwater vehicle malfunction, and an actuator failure model is established. An improved Gaussian particle filtering algorithm is proposed and is used to estimate the AUV failure model and motion state. Bayes algorithm is employed to perform robot fault detection. The sliding window method is adopted for fault magnitude estimation. The feasibility and validity of the proposed method are verified through simulation experiments and experimental data.

• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.10
• /
• pp.928-933
• /
• 2012

In this paper, the IR and compass sensors for the underwater system were used. The walls of the water tank have been recognized and avoided treating the walls as obstacles by the bio-mimetic underwater robot. This paper is consists of two parts: 1.The hardware part for the IR and compass sensors and 2.The software part for obstacle avoidance algorithm while the bio-mimetic robot is swimming with the obstacle recognition. Firstly, the hardware part controls through the RS-485 communications between a microcontroller and the bio-mimetic underwater robot. The software part is simulated for obstacle recognition and collision avoidance based upon the data from IR and compass sensors. Actually, the bio-mimetic underwater robot recognizes where is the obstacle as well as where is the bio-mimetic robot itself while it is moving in the water. While the underwater robot is moving at a constant speed recognizing the wall of water tank as an obstacle, an obstacle avoidance algorithm is applied for the wall following swimming based upon the IR and compass sensor data. As the results of this research, it is concluded that the bio-mimetic underwater robot can follow the wall of the water tank efficiently, while it is avoiding collision to the wall.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1658-1660
• /
• 2000

Simple signs were usually exchanged as the means of underwater communications. As people recently, need more informations for underwater activities, necessities of underwater communication systems exchanging hunman voice are increased. The purpose of this paper is understanding the ordinary characteristics of underwater communication and investigating the necessary conditions for a good underwater communication system by making a basic communication module. The experiment is achieved by applying AM (Amplitude Modulation) which is mainly used for the underwater communication systems and using common ultrasonic transducers. Ultrasonic transducers usually have narrow bandwidth for transducing electrical energy to mechanical energy. For improvement of sound reconstruction, transducers need more bandwidth which covers voice's frequency range, and goof linearity characteristics in this frequency range. As underwater transmissions have many factors to distort signals. Amplitude Modulation is not a proper way for underwater communications. Using digital signal by sampling human voice should be a good way for this systems, because digital communication simplify transmitting signals.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.513-517
• /
• 2006

Autonomous Underwater Vehicles plays specific role in underwater investigation. Generally, this kind of vehicles will move along a planned path for sea bottom or underwater installations inspections, search for mineral deposits along shelves, seeking lost items including bottom mines or for hydrographic measurements. A crucial barrier for it remains the possibility of precise determination of their underwater position. Commonly used radionavigation systems do not work in such circumstances or do not guarantee the required accuracies. In the paper some new solution is proposed on the assumption that it is possible to increase the precision by certain processing of a combination of measurements conducted by means of different techniques. Objective of the paper is the idea of navigation of AUV which consists of two phases: firstly a trip of AUV along pre-planned route and after that postprocessed transformation of collected data in post-processing mode. During the processing of collected data the modern adjustment methods have been applied, mainly estimation by means of least squares and M-estimation. Application of these methods should be associated with the measuring and geometric conditions of navigational tasks and thus suited for specific scientific and technical problems of underwater navigation. The first results of computer aided investigation will be presented and the basic scope of these application and possible development directions will be indicated also. The paper is prepared as an partial results of the works carried out within a framework of the research Project: 'Improvement of the Precise Underwater Vehicle Navigation Methods' financed by the Polish Ministry of Education and Science (No 0 T00A 012 25).

• KIPS Transactions on Computer and Communication Systems
• /
• v.5 no.3
• /
• pp.71-78
• /
• 2016

Recently, The interest about underwater acoustic communication is increase such as marine resources, disaster prevention, weather prediction, and so on. Because the underwater acoustic communication uses a water as media, the underwater acoustic communication has a lot of restrictions. Although the underwater acoustic communication is hard, it is important to consider the security. In this paper, we estimate the performance of cryptographic algorithms(AES, ARIA, and LEA) on a various devices, available in underwater acoustic communication, and analysis the results. This result will be provide effective data confidentiality for underwater communication.