Hyeon Kyu Yoon

Dynamic Modeling and Simulation of a Towing Rope using Multiple Finite Element Method

†Dept. of Naval Architecture & Marine Engineering, Changwon National University, Gyeongnam 641-773, Korea *,**Dept. of Mechanical Engineering, Changwon National University, Gyeongnam 641-773, Korea***Maritime & Ocean Engineering Research Institute, KORDI, Daejeon 305-343, Korea요 약 :예인줄을 여러 개의 유한요소로 분할 한 뒤 각 요소들에 Newton의 운동 제 2법칙을 적용하고 각각에 작용하는 외력은 성분별로 장력, 항력, Coriolis 힘, 중력, 부력, 입수 충격력 등으로 구분하여 예선과 부선을 연결하는 예인줄의 동역학 모델을 정립하였다. 일반적으로 예인줄 요소의 병진 운동만을 고려하는 이전의 연구들과는 달리 본 논문에서는 예인줄 요소의 운동을 횡동요를 제외한 5자유도로 확장하고 외력 고려가 용이한 물체고정좌표계에서 기술하였다. 예인줄 요소들 간에는 연결점에서 인장만 되는 스프링과 감쇠기로 연결하고, 스프링의 강성계수는 실제 적용되는 예인줄의 강성계수와 등가가 되도록 설정하였다. 정립된 예인줄 모델의 검증을 위하여 예인줄의 공기중 및 수면 바로 위에서의 자유낙하, 예인선의 가속운동, 예인선의 조화운동 시나리오에 대하여 시뮬레이션을 수행하였다. 시뮬레이션 결과, 예인선, 부선, 예인줄 요소들의 운동 시계열 값들은 실제 예상치와 유사한 경향을 보이는 것을 확인하였다.핵심용어 : 예인줄, 다물체 요소이론, 예선, 부선, 모델링, 시뮬레이션Abstract : After towing rope connecting a barge to a tug was subdivided into multiple finite elements, then those dynamic models was established using Newtons second law and considering the external force and moment such as tension, drag, Coriolis force, gravity, buoyancy, and impact due to free surface acting on each element. While the previous research on the model of towing rope considered only translation, five-degree-of-freedom equations of motion except roll based on the body-fixed frame were established in this paper. All elements are connected by a spring and a damper, and the stiffness of the spring was set as the equivalent value of the real rope. In order to confirm the established multiple finite element model, various scenarios such as freely falling of towing rope in the air and above the free surface, accelerating of a tug which tows a barge connected by towing rope, and sinusoidal moving of a tug were set up and simulated. As the results, the trajectories of the tug, the barge, and the towing rope showed good tendencies to the ones of real expected situations.Key words :towing rope, multiple finite element method, tug, barge, modeling, simulation †교신저자 : 정회원, hkyoon@changwon.ac.kr 055)213-3683 * 학생회원, aktkssha@nate.com 010)8552-9977 ** 정회원, chong@changwon.ac.kr 055)213-3607*** 정회원, ygkim@moeri.re.kr 042)866-3642

A Simplified Horizontal Maneuvering Model of a RIB-Type Target Ship

AbstractA Rigid Inflatable Boat (RIB) is now widely used for commercial and military purpose. In this paper, it is supposed that seven-meter-class RIB be used a s an unmanned target ship for naval training. In order to develop many tactical maneuvering patterns of a target ship, a simple horizontal maneuvering model of a RIB is needed. There fore, models of speed and yaw rate are constructed as the first-order differential equati ons based on Lewandowskis empirical formula for steady turning circle diameter of a conve ntional planning hull. Some parameters in the models are determined using the results of se a trial tests. Finally, proposed models are validated through the comparison of the sim ulation result with the sea trial result for a specific scenario. Even though a simple model does not represent the horizontal motion of a RIB precisely, however, it can be used enough to develop tactical trajectory patterns. ※Keywords: RIB(고형부력선), Unmanned target ship(무인 표적정), Maneuvering model(조종모델), Sea trial(실선 시운전), Tactical pattern(전술 패턴)

A Study on the Model Test Scheme for Establishing the Mathematical Model of Hydrodynamic Force and Moment Acting on a Slowly Moving Ship

The mathematical models of hydrodynamic force and moment acting on a ship at low speed range should be established differently from the ones at nominal cruising speed range since a ship moves with large drift angle or rotates in a stationary position. We modified widely used Yoshimura`s cross flow model in order to apply the system identification method to estimate parameters in the model. The apparatus and the procedure of free running model test were suggested so that the parameters in the model be estimated. The validity of our proposing modified model and test procedure was confirmed by comparison with the results of simulated model test.

Depth Controller Design for Submerged Body Moving near Free Surface Based on Adaptive Control

A submerged body moving near the free surface needs to maintain its attitude and position to accomplish missions. It is necessary to validate the performance of a designed controller before a sea trial. The hydrodynamic coefficients of maneuvering are generally obtained by experiments or computational fluid dynamics, but these coefficients have uncertainty. Environmental loads such as the wave exciting force and suction force act on the submerged body when it moves near the free surface. Thus, a controller for the submerged body should be robust to parameter uncertainty and environmental loads. In this paper, the six-degree-of-freedom equations of motions for the submerged body are constructed. The suction force is calculated using the double Rankine body method. An adaptive control method based on an artificial neural network and proportional-integral-derivative control are used for the depth controller. Simulations are performed under various depth and speed conditions, and the results show the effectiveness of the designed controller.

A Study for the Conceptual Design of a Small Leisure Boat Handling Simulator

ABSTRACTIn this study, a conceptual study was performed for the leisure boat simulator used for navigation training. The aim of this work was to secure the basic operational capability of a leisure boat as a simulated driving device for a general novice operator. A leisure boat simulator was designed to support a user more efficiently regarding navigation proficiency and safety training, as well as to minimize the limitation of place and time and it conveniently and cheaply. A cockpit for navigation status display and operational input, 3D visualization graphic device, and parallel display device were designed to give the trainee a maximum sense of reality by applying a motion platform with six degree of freedom, in which disturbance movement such waves, winds, and tide were simulated for the operator. Leisure boat simulator training scenario was developed by analysis of water-related leisure activities act and sea traffic safety act. Key words : Boat simulator, Scenario, Power boat, Boat operator’s license, Korea coast guard, Water-related leisure activities act, Water leisure sport요 약본 논문에서는 조종이 미숙한 일반인을 위한 모의운전장치로서 보트 운항능력 확보를 위한 레저보트 시뮬레이터 개념설계에 관한 연구를 수행하였다. 레저보트 조종시뮬레이터 요구조건을 도출하기 위하여 국내 ․ 외 해양레저산업의 현황을 분석하고 레저보트와 관련된 사고유형과 국내 해양레저관련 제도와 법규에 대하여 분석하였다 . 레저보트 보유현황을 기반으로 20 ft 및 40 ft급 파워보트를 개발대상 선박으로 선정하였으며 , 실제 레저보트의 운항환경과 동일한 환경을 구현하여 훈련의 집중도와 현실감을 최대화 할 수 있도록 레저보트 시뮬레이터를 설계하였다 . 특히, 레저보트의 운항특성 및 운동특성을 보다 정확히 구현하기 위하여 선박의 형상특성과 해상상태가 반영된 파워보트의 6자유도 운동 수학모형을 개발하여서 , 파도 ․ 바람 ․ 조류 등 외란 중 운동을 재현하는 조종자용 6자유도 모션플랫폼을 적용하여 훈련의 현실감을 극대화 할 수 있도록 레저보트 시뮬레이터를 설계하였다. 조종면허, 조종숙련도 향상을 위하여 국내 조종면허제도와 수상레저안전법 , 해상교통안전법 등을 분석하여 교육 시나리오를 설계하였다 .주요어 : 보트시뮬레이터, 시나리오, 파워보트, 동력수상레저기구 조종면허, 해양경찰, 수상레저안전법, 수상레저

Coupled Dynamic Simulation of a Tug-Towline-Towed Barge based on the Multiple Element Model of Towline

Recently, tug boats are widely used for towing a barge which transports building materials, a large block of a ship, offshore crane, and so on. In order to simulate the dynamics of the coupled towing system correctly, the dynamics of the towline should be well modeled. In this paper, the towline was modeled as the multiple finite elements, and each element was assumed as a rigid cylinder which moves in five degrees of freedom except roll. The external tension and its moment acting on each element of the towline were modeled depending on the position vectors direction. Tugboats motion was simulated in six degrees of freedom where wave and current effects were included, and towed barge was assumed to move in the horizontal plane only. In order to confirm the mathematical models of the coupled towing systems, standard maneuvering trials such as course changing maneuver, turning circle test and zig-zag test were simulated. In addition, the same trials were simulated when the external disturbances like wave and current exist. As the result, it is supposed that the results might be qualitatively reasonable.

A Numerical Study on the Characteristics of a Thick Flapped Rudder depending on Various Geometric Parameters using Computational Fluid Dynamics Technique

A marine flapped rudder is designed to improve the effective lift generated by the rudder; this also improves the maneuverability of the ship. The...

Modeling and Simulation for the Initial Dynamics of a High Speed Underwater Vehicle Ejected from a Submerged Mother Ship

ABSTRACT Heavy-weight high speed underwater vehicle(HSUV) is launched from the submerged mother ship. For the safety point of view, it is important to confirm whether the HSUV would touch the launching mother ship. In this paper, the hydrodynamic force and moment were modeled by the polynomials of motion variables and the simple lift and drag acting on a plate and cylinder which consist of the HSUV’s several parts. The mother ship was assumed as the Rankine half body to consider the flow field near the moving ship. Such hydrodynamic force and moment were included in the 6 DOF equations of motion of the HSUV and the dynamic simulations for the various conditions of the HSUV until the propeller activation were performed. Developed simulation program is expected to reduce the number of expensive sea trial test to develop safety logic of the HSUV at the initial firing stage.Key Words : High Speed Underwater Vehicle(고속 수중운동체), Modeling and Simulation(모델링 및 시뮬레이션), Initial Firing Stage(초기 발사단계), Dynamics(동력학)

Motion Analysis of an Underwater Vehicle Running near Wave Surface

A cylinder-type underwater vehicle for military use that is running near the free surface at the final homing stage to hit a surface ship target is affected by wave force and moment. Since wave can affect an underwater vehicle running at the depth less than half of the modal wave length, it is important to confirm that the underwater vehicle can work well in such a situation. In this paper, wave force and moment per unit wave amplitude depending on wave frequency, wave direction, and vehicle’s running depth were calculated by 3-Dimensional panel method, and the numerical results were modeled in external force terms of six degrees of freedom equations of motion. Motion simulation of the underwater vehicle running in various speed, depth, and sea state were performed.

Modeling and Simulation of the 6 DOF Motion of a High Speed Planing Hull Running in Calm Sea

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 Lewandowskis empirical formula and the speed-dependent equilibrium state are calculated beforehand by Savitskys 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.