Jin-Hyeong Ahn - Academia.edu (original) (raw)
Papers by Jin-Hyeong Ahn
Journal of the Korea Institute of Military Science and Technology, Aug 5, 2015
Recently, unmanned systems are largely utilized in various fields due to the persistency and the ... more Recently, unmanned systems are largely utilized in various fields due to the persistency and the least operational risk and an unmanned surface vehicle(USV) is the one of the representative application in the naval field. To assign multiple roles to an USV, we developed a sonar system which consists of a forward detecting sonar for the long-range detection, a downward detecting sonar for the small target scan and identification, and a strut type body for mounting sonar systems. In this paper, we described the developed sonar system for USV and the sea test results for verifying system performance. The test results showed that the developed sonar system was able to detect the underwater target about several kilometers away and could recognize a small object at the downside of the sonar system. We expect that the developed sonar system will be easily applied to other unmanned platforms without serious consideration.
Journal of Ocean Engineering and Technology, Jun 30, 2023
In the design of submarines, frequent reviews are conducted regarding the hydrodynamic characteri... more In the design of submarines, frequent reviews are conducted regarding the hydrodynamic characteristics acting on the hull. A review of the hydrodynamic characteristics may include speed performance, maneuverability, and exceptional purpose performance. Generally, shipyards and research institutions worldwide have accumulated data (model tests, sea trials, and numerical analysis) based on their technology, research, development, and experience in surface ships for an extended period. These data are used frequently in the initial and detailed design of surface ships. On the other hand, in the case of submarines, unlike in surface ships, only a minimal amount of model test data, sea trial data, and numerical analysis data can be relied upon. This situation is also characterized by significantly reduced accessibility. Furthermore, in the case of submarines, the maneuvering performance in underwater operation is mentioned as an important factor closely related to submarine construction. In particular, submarines require considering the maneuvering performance for six degrees of freedom (DOF) of the hull, which makes it more challenging to deal with than maneuvering surface ships. Thus far, the performance estimation of submarine maneuverability has followed the same procedure (using the mathematical model of maneuvering motion based on captive model tests) as that used in surface ships, but the complexity of the procedure must be considered as the degree of freedom of the considered maneuvering increases. On the other hand, a representative method of estimating maneuvering performance using the six degrees of freedom (hereinafter 6DOF) maneuvering mathematical model proposed by Gertler and Hagen (1967) and Feldman (1979) is to use the mathematical model-based methods for submarine maneuvering. Generally, in methods based on mathematical models, it is essential to obtain hydrodynamic derivatives, which are the hydrodynamic forces included in the mathematical model. In the case of submarines, it is also essential to obtain hydrodynamic forces acting on the hull
Journal of Ocean Engineering and Technology
This paper introduces a simulation-based determination method for hydrodynamic derivatives and 6D... more This paper introduces a simulation-based determination method for hydrodynamic derivatives and 6DOF (degrees-offreedom) motion analysis for an underwater vehicle. Hydrodynamic derivatives were derived from second-order modulus expansion and composed of the added mass, and linear and nonlinear damping coefficients. The added mass coefficients were analytically obtained using the potential theory. All of the linear and nonlinear damping coefficients were determined using CFD simulation, which were performed for various cases based on the actual operating condition. Then, the linear and nonlinear damping coefficients were determined by fitting the CFD results, which referred to 6DOF forces and moments acting on an underwater vehicle, with the least square method. To demonstrate the applicability of the current study, 6DOF simulations for three different scenarios (L-, U-, and S-turn) were carried out, and the results were validated on the basis of physical plausibility.
Institute of Control, Robotics and Systems, Sep 1, 2013
Journal of the Society of Naval Architects of Korea, 2018
Planing hull type ships are often equipped with interceptor or trim tab to improve the excessive ... more Planing hull type ships are often equipped with interceptor or trim tab to improve the excessive trim angle which leads to poor resistance and sea keeping performances. The purpose of this study is to design a controller to control the attitude of the ship by controllable stern interceptor and validate the effectiveness of the attitude control by the towing tank test. Embedded controller, servo motor and controllable stern interceptor system were equipped with planing hull type model ship. Prior to designing the control algorithm, a model test was performed to identify the system dynamic model of the planing hull type ship including the stern interceptor. The matrix components of model were optimized by Genetic Algorithm. Using the identified model, PID controller which is a classical controller and sliding mode controller which is a nonlinear robust controller were designed. Gain tuning of the controllers and running simulation was conducted before the towing tank test. Inserting the designed control algorithm into the embedded controller of the model ship, the effectiveness of the active control of the stern interceptor was validated by towing tank test. In still water test with small disturbance, the sliding mode controller showed better performance of canceling the disturbance and the steady-state control performance than the PID controller.
Journal of the Korea Society for Simulation, 2012
In this study, underwater behaviors of negative buoyant body and positive buoyant body, which are... more In this study, underwater behaviors of negative buoyant body and positive buoyant body, which are ejected from a platform, are compared through eject test and simulation. CFD(Computational Fluid Dynamics) method is used to calculate the hydrodynamic derivatives of negative buoyant body with varied hull. Hydrodynamic derivatives that cannot be calculated with CFD are used with the same values of base shape. The pitch angles of test data are much bigger than those of simulated data, and the reason is supposed to be the trailing air effect. A more accurate simulation is possible via modified force modeling which reflects this phenomenon. The underwater behaviors of positive buoyant body and negative buoyant body are somewhat different with each other at the same eject condition, but it may not be a problem in the view of operation.
Journal of the Korea Institute of Military Science and Technology, 2015
Recently, unmanned systems are largely utilized in various fields due to the persistency and the ... more Recently, unmanned systems are largely utilized in various fields due to the persistency and the least operational risk and an unmanned surface vehicle(USV) is the one of the representative application in the naval field. To assign multiple roles to an USV, we developed a sonar system which consists of a forward detecting sonar for the long-range detection, a downward detecting sonar for the small target scan and identification, and a strut type body for mounting sonar systems. In this paper, we described the developed sonar system for USV and the sea test results for verifying system performance. The test results showed that the developed sonar system was able to detect the underwater target about several kilometers away and could recognize a small object at the downside of the sonar system. We expect that the developed sonar system will be easily applied to other unmanned platforms without serious consideration.
Journal of Institute of Control, Robotics and Systems, 2013
Applied Ocean Research, 2012
In this paper, the fuzzy inference system combined with an expert system is applied to collision ... more In this paper, the fuzzy inference system combined with an expert system is applied to collision avoidance system. Especially, calculation method of the collision risk by using neural network is proposed. At first, the membership functions of DCPA and TCPA are determined on the basis of simulation results using the KT equations. And then, the inference table is redesigned by using the ANFIS (Adaptive Network-based Fuzzy Inference System) algorithm. Secondly, additional factors, the ship domain, topological characteristics and restricted visibility, which can affect navigator's reasoning of the collision risk besides DCPA and TCPA are considered. Finally, MLP (Multilayer Perceptron) neural network to the collision avoidance system is applied to make up for fuzzy logic.
Proceedings of the Korean Institute of Navigation and Port Research Conference, 2005
Journal of the Korea Institute of Military Science and Technology, Aug 5, 2015
Recently, unmanned systems are largely utilized in various fields due to the persistency and the ... more Recently, unmanned systems are largely utilized in various fields due to the persistency and the least operational risk and an unmanned surface vehicle(USV) is the one of the representative application in the naval field. To assign multiple roles to an USV, we developed a sonar system which consists of a forward detecting sonar for the long-range detection, a downward detecting sonar for the small target scan and identification, and a strut type body for mounting sonar systems. In this paper, we described the developed sonar system for USV and the sea test results for verifying system performance. The test results showed that the developed sonar system was able to detect the underwater target about several kilometers away and could recognize a small object at the downside of the sonar system. We expect that the developed sonar system will be easily applied to other unmanned platforms without serious consideration.
Journal of Ocean Engineering and Technology, Jun 30, 2023
In the design of submarines, frequent reviews are conducted regarding the hydrodynamic characteri... more In the design of submarines, frequent reviews are conducted regarding the hydrodynamic characteristics acting on the hull. A review of the hydrodynamic characteristics may include speed performance, maneuverability, and exceptional purpose performance. Generally, shipyards and research institutions worldwide have accumulated data (model tests, sea trials, and numerical analysis) based on their technology, research, development, and experience in surface ships for an extended period. These data are used frequently in the initial and detailed design of surface ships. On the other hand, in the case of submarines, unlike in surface ships, only a minimal amount of model test data, sea trial data, and numerical analysis data can be relied upon. This situation is also characterized by significantly reduced accessibility. Furthermore, in the case of submarines, the maneuvering performance in underwater operation is mentioned as an important factor closely related to submarine construction. In particular, submarines require considering the maneuvering performance for six degrees of freedom (DOF) of the hull, which makes it more challenging to deal with than maneuvering surface ships. Thus far, the performance estimation of submarine maneuverability has followed the same procedure (using the mathematical model of maneuvering motion based on captive model tests) as that used in surface ships, but the complexity of the procedure must be considered as the degree of freedom of the considered maneuvering increases. On the other hand, a representative method of estimating maneuvering performance using the six degrees of freedom (hereinafter 6DOF) maneuvering mathematical model proposed by Gertler and Hagen (1967) and Feldman (1979) is to use the mathematical model-based methods for submarine maneuvering. Generally, in methods based on mathematical models, it is essential to obtain hydrodynamic derivatives, which are the hydrodynamic forces included in the mathematical model. In the case of submarines, it is also essential to obtain hydrodynamic forces acting on the hull
Journal of Ocean Engineering and Technology
This paper introduces a simulation-based determination method for hydrodynamic derivatives and 6D... more This paper introduces a simulation-based determination method for hydrodynamic derivatives and 6DOF (degrees-offreedom) motion analysis for an underwater vehicle. Hydrodynamic derivatives were derived from second-order modulus expansion and composed of the added mass, and linear and nonlinear damping coefficients. The added mass coefficients were analytically obtained using the potential theory. All of the linear and nonlinear damping coefficients were determined using CFD simulation, which were performed for various cases based on the actual operating condition. Then, the linear and nonlinear damping coefficients were determined by fitting the CFD results, which referred to 6DOF forces and moments acting on an underwater vehicle, with the least square method. To demonstrate the applicability of the current study, 6DOF simulations for three different scenarios (L-, U-, and S-turn) were carried out, and the results were validated on the basis of physical plausibility.
Institute of Control, Robotics and Systems, Sep 1, 2013
Journal of the Society of Naval Architects of Korea, 2018
Planing hull type ships are often equipped with interceptor or trim tab to improve the excessive ... more Planing hull type ships are often equipped with interceptor or trim tab to improve the excessive trim angle which leads to poor resistance and sea keeping performances. The purpose of this study is to design a controller to control the attitude of the ship by controllable stern interceptor and validate the effectiveness of the attitude control by the towing tank test. Embedded controller, servo motor and controllable stern interceptor system were equipped with planing hull type model ship. Prior to designing the control algorithm, a model test was performed to identify the system dynamic model of the planing hull type ship including the stern interceptor. The matrix components of model were optimized by Genetic Algorithm. Using the identified model, PID controller which is a classical controller and sliding mode controller which is a nonlinear robust controller were designed. Gain tuning of the controllers and running simulation was conducted before the towing tank test. Inserting the designed control algorithm into the embedded controller of the model ship, the effectiveness of the active control of the stern interceptor was validated by towing tank test. In still water test with small disturbance, the sliding mode controller showed better performance of canceling the disturbance and the steady-state control performance than the PID controller.
Journal of the Korea Society for Simulation, 2012
In this study, underwater behaviors of negative buoyant body and positive buoyant body, which are... more In this study, underwater behaviors of negative buoyant body and positive buoyant body, which are ejected from a platform, are compared through eject test and simulation. CFD(Computational Fluid Dynamics) method is used to calculate the hydrodynamic derivatives of negative buoyant body with varied hull. Hydrodynamic derivatives that cannot be calculated with CFD are used with the same values of base shape. The pitch angles of test data are much bigger than those of simulated data, and the reason is supposed to be the trailing air effect. A more accurate simulation is possible via modified force modeling which reflects this phenomenon. The underwater behaviors of positive buoyant body and negative buoyant body are somewhat different with each other at the same eject condition, but it may not be a problem in the view of operation.
Journal of the Korea Institute of Military Science and Technology, 2015
Recently, unmanned systems are largely utilized in various fields due to the persistency and the ... more Recently, unmanned systems are largely utilized in various fields due to the persistency and the least operational risk and an unmanned surface vehicle(USV) is the one of the representative application in the naval field. To assign multiple roles to an USV, we developed a sonar system which consists of a forward detecting sonar for the long-range detection, a downward detecting sonar for the small target scan and identification, and a strut type body for mounting sonar systems. In this paper, we described the developed sonar system for USV and the sea test results for verifying system performance. The test results showed that the developed sonar system was able to detect the underwater target about several kilometers away and could recognize a small object at the downside of the sonar system. We expect that the developed sonar system will be easily applied to other unmanned platforms without serious consideration.
Journal of Institute of Control, Robotics and Systems, 2013
Applied Ocean Research, 2012
In this paper, the fuzzy inference system combined with an expert system is applied to collision ... more In this paper, the fuzzy inference system combined with an expert system is applied to collision avoidance system. Especially, calculation method of the collision risk by using neural network is proposed. At first, the membership functions of DCPA and TCPA are determined on the basis of simulation results using the KT equations. And then, the inference table is redesigned by using the ANFIS (Adaptive Network-based Fuzzy Inference System) algorithm. Secondly, additional factors, the ship domain, topological characteristics and restricted visibility, which can affect navigator's reasoning of the collision risk besides DCPA and TCPA are considered. Finally, MLP (Multilayer Perceptron) neural network to the collision avoidance system is applied to make up for fuzzy logic.
Proceedings of the Korean Institute of Navigation and Port Research Conference, 2005