• 대한조선학회논문집
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• 제60권3호
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• pp.165-174
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• 2023

Unmanned Surface Vehicle (USV)'s berthing and unberthing is the most difficult maneuvering tasks and have the highest risk of accidents. In this paper, we designed a berthing/unberthing control algorithm given human joystick command for an USV equipped with a waterjet and a bow thruster. The berthing and unberthing maneuvers are performed remotely by a joystick operator at the Ground Control Center (GCC) where the status of USV and environmental situation can be monitored. We interpret the human joystick commands into USV's desired speed, yaw rate, and heading angle commands. next, we developed a control algorithm for the desired target values of MIMO actuators (engine speed, bucket step, nozzle angle, and bow thruster state) to follow the interpreted commands. The validity of the control algorithm is confirmed through simulations and sea trials at Gwang Am port.

• 수산해양교육연구
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• 제27권6호
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• pp.1865-1871
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• 2015

Ship's trim is the one of the most important factor for safety at the sea. Turning circle test and Z-test were carried out to find the effect of ship's trim and draft changes. The results are as follows. 1. If the ship's draft and trim became large, turning circle would be wide. 2. If the ship's draft and trim became large, ship's drift angle would be small. Small drift angle made wide turning circle. 3. Trim by the head made slow ship's final speed when turning circle test. 4. By Z-test, the deeper draft and trim by the stern made small OSA. Small OSA means strong ship's stability. 5. Totally 2nd OSA is smaller than 1st OSA on Z-test. 6. There were small differences of 2nd OSA in trim by the stern, but there were large OSA in trim by the head. 7. The larger trim by the stern, the smaller OSW. The small OSW means better ship's stability and maneuverability.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.232-236
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• 2003

The anchor is laid on seabed and the main engine is worked to against incident environmental loads in typoon. As the main engine is broken down in the storm, the anchor chain is cutted and the vessel is drifted. Although a ship is moored by two point mooring lines to keep the her position, a ship is crashed into a rock because of typoon and the accident of oil spilling may be occured. In this paper, we studied the position-keeping of a ship which is analyized based on the slow motion maneuvering equations considering wave, current and wind. The direct integration method is employed to estimate wave loads. The current forces are calculated by using mathematical of MMG. The two point mooring forces are quasisatatically evaluated by using the catenary equation. The coefficeints of wind forces are modeled from Isherwood’s emperical data and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two point moored ship are simulated considering wave, current, wind load in time domain.

• 한국정밀공학회지
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• 제33권4호
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• pp.257-264
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• 2016

Solid state joining techniques are increasingly applied in a wide range of industrial applications. Friction welding is a solid state welding technique that is used to join similar or dissimilar materials. In this study, friction welding was applied to rotor shaft composed of a disk and a shaft. The disk and shaft were manufactured by hot forging and rolling, respectively. The aim of the study was to predict the structural characteristics during hot forging and friction welding process for rotor shaft of turbo charger. The structural characteristics were determined by heat input and heat affected zone (HAZ) during a short cycle time. Thus, transient FE analysis for hot forging and friction welding was based on heat transfer. The results were used to predict structural characteristics during hot forging and friction welding processes. The prototype of rotor shaft was manufactured by the result-based process parameters.

• 소성∙가공
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• 제20권3호
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• pp.236-242
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• 2011

The two objectives of this study were, first, to determine the optimal friction welding process parameters using finite element simulations and, second, to evaluate the mechanical properties of the friction welded zone for large piston rods in marine diesel engines. Since the diameters of the rod and its connecting part are very different, the manufacturing costs using friction welding are reduced compared to those using the forging process of a single piece. Modeling is a generally accepted method to significantly reduce the number of experimental trials needed when determining the optimal parameters. Therefore, because friction welding depends on many process parameters such as axial force, initial rotational speed and energy, amount of upset and working time, finite element simulations were performed. Then, friction welding experiments were carried out with the optimal process parameter conditions resulting from the simulations. The base material used in this investigation was AISI 4140 with a rod outer diameter of 280 mm and an inner diameter of 160 mm. In this study, various investigation methods, including microstructure characterization, hardness measurements and tensile and fatigue testing, were conducted in order to evaluate the mechanical properties of the friction welded zone.

• 한국항해학회지
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• 제16권3호
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• pp.19-31
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• 1992

The Navigational System is the Fundamental System of Port Transportation System and comprises 3 Subsystems, say, the Waterway System, the Shiphandling System and the Support System. The Waterway System of Navigational System is the important and fundamental System for Traffic Safety inside the Port like a Car Road System on Land. This study aims to make a Guideline for the Optimal Waterway System of Port Development and Safety. The Conclusion of this Paper are drawn : 1) The complicated Shiphandling Operations should be avoided for the period of Physical night Time for eliminating the Human Errors. 2) For the Maneuverability and all-weather Combined Piloting the Inside Turn Point Buoy and Begin the-turn Buoy should be mounted with Racon(T) and Radar Reflector for foggy and bad weathers. 3) The Seabuoy located in the Approaching Area for Pilot Station and making Landfall should be mounted with Racon(G) and Morese A Light for giving a Hint of Pilot Station to the Captain on the Bridge, and these Equipments of Racon and Light should be operated normally and effectively even in a Heavy and stormy weathers. 4) A Basic Practical Expression, 1/2 L sin D, for calculating the Extra Width of Cutoff Turn Regions was derived Originally from the Viewpoint of Turn Maneuvers and Maneuverability of the Ship.

• 대한조선학회논문집
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• 제36권1호
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• pp.22-29
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• 1999

선박의 고속화에 따라서 선체를 부양시키거나 자세를 제어하기 위하여 높은 양력을 발생시키는 장치의 필요성이 증대하게 되었다. 뿐만 아니라 해양오염방지를 위하여 IMO 등의 국제기구에서는 대형 신조선에 대하여 충분한 조종성능을 확보할 것을 권장하고 있어서 높은 양력을 발생시키는 타의 필요성이 증대하게 되었다. 높은 양력을 얻는 문제는 항공분야에서 오래 전부터 핵심적인 문제로 다루어져 왔으며 그중 대표적인 것이 Coanda장치이다. 방형비척계수가 크고 길이-폭비가 작은 저속비대선에서는 통상적인 타를 부착한 경우에 높은 양력을 얻기 어려우므로 플랩이 부탁된 타를 선정하고 이에 Coanda장치를 도입하였을 때 성능이 향상되는 것을 선형시험수조에서 실험적으로 확인하고자 하였다.

• 한국해양공학회지
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• 제18권3호
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• pp.8-12
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• 2004

The anchor is laid on the seabed, and the main engine is working against incident environmental loads in a typhoon. As the main engine is broken Mum in the storm, the anchor chain is cut and the vessel drifts. Although a ship is moored by two-point mooring lines to maintain her position, it has crashed into a rock because of a typhoon, resulting in a possible accidental oil spillage. In this paper, we studied maintenance of a ship's position, which is analyzed based on the slow motion maneuvering equations considering wave, current, and wind. To estimate wave loads, the direct integration method is employed. The current forces are calculated, using MMG (Mathematical Modeling Group). Th two-point mooring forces are quasi-statistically evaluated, using the catenary equation. Th coefficients of wind forces are modeled from Isherwood's empirical data, and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two-point moored ship are simulated, considering wave, current, and wind load, in specific domain of time.

• 한국항해학회지
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• 제20권3호
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• pp.13-30
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• 1996

It is general that large ships entering or leaving a port located in the East coast of Korean peninsular are often exposed athwart to swell while maneuvering in the vicinity of breakwater at harbor enterance or to prevailing wind inside the port in winter. Particulary, Many VLCCs laden with ore coal are calling at Pohang Port, on account of which it is likely that one of those VLCCs block the port if they were to run aground in fairway due to adverse circumstance of swell, prevailing winds or improper shiphandling. This accident may result in delay of delivery of raw material for Pohang Steel Mill which will bring about shortcomings of steel products for nationwide relevant industries causing national economic shock. Therefore, This study basically aims at establishment of certain criteria for safe unberthing of VLCC in this port to prevent such unexpected disaster because any VLLC is highly affected by external forces when in ballast condition. Computer simulations are unavoidable to fulfull this study successfuly and many simulations have been carried out repeatedly to find a model of safe unberthing under various unfavourable wind conditions. The "PC-based ship maneuvering simulator for training purpose" was used to perform numerous simulations at the least economic burden and to verify its availability that it can be used not only for training but also some other purposes. purposes.

• 대한조선학회논문집
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• 제53권1호
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• pp.10-17
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• 2016

When a planing hull straightly runs and turns, its floating position and pitch angle are changed depending on its speed, and large transient motion happens. In this paper, six degrees of freedom(6 DOF) equations of motion, which could simulate the motion of a planing hull, are established. Static and dynamic forces in vertical plane are modeled using pre-calculated displacements and metacentric heights depending on various draft, lift under bottom, and vertical damping coefficients which are used to tune the final motion. Hydrodynamic coefficients in horizontal plane at various equilibrium state are calculated by using Lewandowski's empirical formula and the speed-dependent equilibrium state are calculated beforehand by Savitsky's formula. The speed effects are considered by curve-fitting the coefficients at various speed to the polynomials. Accelerating, decelerating and backing, turning, and zig-zag are simulated and compared with the sea trial results, and it is confirmed that the speed reduction, roll, and pitch during such maneuvers of sea trial and simulation are well consistent.