• Journal of Korea Multimedia Society
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• v.15 no.4
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• pp.560-568
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• 2012

As for the implementation technology of virtual space, the experience method becomes multifunctional and it recognizes movement, sound, temperature and pressure and is expanding to the studies on the interaction possible intelligent interaction technology field between contents and users. The virtual reality technology is being studied to apply the 3D graphic technology and physical phenomena to virtual space to increase the sense of reality and use hardware devices to the virtual environment to increase immersive experience. The production of interactive contents about the virtual underwater environment needs bidirectional interface technology to connect hardware devices and ocean contents in order to increase the sense of a user to increase the sense of immersion. In this study, it tried to express the virtual underwater environment with the sense of actuality and reality from the analysis of the environmental factors according to changes in depth of water and from the application of the normalized underwater physical laws. Also it was to develop sensory contents having to experience the skin scuba without directly entering the water by connecting a sensory simulator about the skin scuba with the virtual underwater environment.

• Journal of Korea Multimedia Society
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• v.17 no.1
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• pp.104-112
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• 2014

With recent development of virtual reality technology, coupled with the growth of the marine industry, virtual underwater simulation systems are under development in various studies, for educational purposes and to simulate virtual reality experiences. Current literature indicates many underwater simulation systems to date have focused on the quality of visual stimulus delivered through three-dimensional graphics user interface, limiting the reality of the experience. In order to improve the quality of the reality delivered by such virtual simulations, it is crucial to develop multi-sensory technology rather than focus on the conventional audio-visual interaction, which limits experiencer from the sense of underwater immersion and existence within the simulation. This work proposes the immersive multi-sensory effector system, delivering the users with a more realistic underwater experience. The sense of reality perceived was evaluated, as the main factor of the virtual reality system.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.2
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• pp.124-130
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• 2005

Obstacle avoidance of underwater robots based on a modified virtual force field algorithm is proposed in this paper. The VFF(Virtual Force Field) algorithm, which is widely used in the field of mobile robots, is modified for application to the obstacle avoidance of underwater robots. This Modified Virtual Force Field(MVFF) algorithm using the fuzzy lgoc can be used in moving obstacles avoidance. A fuzzy algorithm is devised to handle various situations which can be faced during autonomous navigation of underwater robots. The proposed obstacle avoidance algorithm has ability to handle multiple moving obstacles. Results of simulation show that the proposed algorithm can be efficiently applied to obstacle avoidance of the underwater robots.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.4
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• pp.498-504
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• 2005

A fuzzy logic for collision avoidance of underwater robots is proposed in this paper. The VFF(Virtual Force Field) method, which is widely used in the field of mobile robots, is modified for application to the autonomous navigation of underwater robots. This Modified Virtual Force Field(MVFF) method using the fuzzy logic can be used in either track keeping or obstacle avoidance. Fuzzy logics are devised to handle various situations which can be faced during autonomous navigation of underwater robots. The obstacle avoidance algorithm has the ability to handle multiple static obstacles. Results of simulation show that the proposed method can be efficiently applied to obstacle avoidance of the underwater robots.

• The Journal of the Korea institute of electronic communication sciences
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• v.2 no.3
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• pp.157-162
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• 2007

The goal of researching a proper crowd animation is to design system that is satisfied with the reality of scenes, performance of system, and interaction with users to show the crowd vividly and effectively in virtual underwater world. In this paper, we smartly expressed the behavior patterns for flocks of fish in virtual underwater and we made up for the weak points in spending time and cost to produce crowd animation. We compared with the number of mesh, the number of fish, the number of frame, elapsed time, and resolution and analyzes them with the fish behavior simulating system. We developed a virtual underwater simulator using this system.

• Journal of the Korea Society for Simulation
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• v.27 no.4
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• pp.27-45
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• 2018

The terrestrial communication network and the underwater acoustic communication network have very different communication characteristics each other in operational environments, communication media, propagation delay, frequency bandwidth, transmission speed, bit error rate, and so on. These different characteristics cause some different address schemes and different maximum transmission units and, as a result, these differences must form certainly obstacles to the intercommunication between a terrestrial communication network and an underwater acoustic communication network. In this paper, we presents a method to use the virtual addresses to resolve the interconnection problem caused by different address schemes between a terrestrial communication network and an underwater acoustic communication network, and, through a mathematical modeling, we analyze the performance on the message transceiving delay time in the underwater environment.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.443-450
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• 2018

A receiving array system can be applied for tonal noise analysis of underwater vehicles, but it is difficult to install and operate, and a lot of cost is required. In order to overcome this problem, this paper proposes a method to measure the tonal noise of underwater vehicle after synthesizing a virtual array using single receiver. The proposed method compensates the Doppler frequency and time delay caused by the movement of the underwater sound source and applies the focused beamforming technique. The performance of the proposed method was analyzed via simulation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.256-265
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• 2017

In this paper, an ascheme is proposed for multiuser underwater acoustic communication by using the multi-chirp rate signals. It differs from the well known TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access) or CDMA (Code Division Multiple Access), by assigning each users with different chirp-rate carriers instead of the time, frequency or PN code. Multi-chirp rate signals can be separated from each other by FrFT (Fractional Fourier Transform), which can be regarded as the chirp-based decomposing, and superior to the match filter in the underwater acoustic channel. VTRM (Virtual Time Reverse Mirror) is applied into the system to alleviate the ISI caused by the multipatch and make the equalization more simple. Results of computer simulations and pool experiments prove that the proposed multiuser underwater acoustic communication based on the multi-chirp rate exhibit well performance. Outfield experments carrie out in Xiamen Port show that using about 10 kHz bandwidth, four users could communicate at the same time with 425 bps with low BER and can match the UAC application.

• Journal of Ocean Engineering and Technology
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• v.23 no.5
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• pp.61-70
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• 2009

An AUV (Autonomous Underwater Vehicle) is an unmanned underwater vessel to investigate sea environments and deep sea resource. To be completely autonomous, AUV must have the ability to home and dock to the launcher. In this paper, we consider a class of homing trajectory planning problem for an AUV with kinematic and tactical constraints in horizontal plane. Since the AUV under consideration has underactuated characteristics, trajectory for this kind of AUV must be designed considering the underactuated characteristics. Otherwise, the AUV cannot follow the trajectory. Proposed homing trajectory panning method that called VGM (Virtual Goal Method) based on visibility graph takes the underactated characteristics into consideration. And it guarantees shortest collision free trajectory. For tracking control, we propose a PD controller by simple guidance law. Finally, we validate the trajectory planning algorithm and tracking controller by numerical simulation and ocean engineering basin experiment in KORDI.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.935-937
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• 1999

In this study, 1-3 type composite specimens were fabricated with PZT powders prepared by the molten-salt synthesis method and Eccogel polymer matrix. A virtual level-meter was fabricated with a 1-3 type composite probe and electronic unit for underwater application. There was no difference in values between a virtual and measured level on its level meter.