Jaeyong Lee

자율운항 선박의 접안을 시뮬레이션하기 위해서는 선박과 안벽 사이의 접촉을 감지하는 것이 필수적이다. 현재 자율운항 선박의 알고리즘 검증을 위한 시뮬레이션은 대부분 2차원 평면에서 이루어지고 있다. 본 논문에서는 3차원 시뮬레이션에서 개체 간의 접촉 여부뿐 아니라 접촉 지점까지 추출하기 위한 경계 제적의 생성 기법을 제시한다. 복잡한 형태의 선체를 4개로 분할하고, V-HACD 방법을 분할된 선체에 순차적으로 적용한다. 평평한 부분이 대부분인 선체의 중앙부에 대해서는 V-HACD 알고리즘의 한계로 인해 세분화 작업을 별도로 진행한다. 이후 충돌 감지용 소프트웨어를 활용하여 계층화된 구조체에 대하여 안벽과의 접촉과 관련한 설정을 진행한다. 시뮬레이션을 통해 사등분된 선체에 대해 각각 수행된 세분화 결과물들을 하나의 선체로 통합하는 과정이 정상적으로 이루어지는 것을 확인하였다. 접안 시뮬레이션에서 선체 측면의 접촉 위치가 1m의 정밀도로 성공적으로 검출되었다. 제시된 방법은 선박의 접안 제어 알고리즘의 성능을 검증하는 시뮬레이션 기법을 고도화하는 데 사용될 수 있을 것이다.

To evaluate the time-domain positioning performance of arctic marine structures, it is necessary to generate an ice load appropriate for the current position and heading of the structure. The position and orientation angle of a floating body continuously change with time. Therefore, an ice load is required for any attitude in the time-domain simulation. In this study, we present a fundamental technique for analyzing ice loads in the frequency domain based on data measured at various angles in the ice-water tank experiment. We perform spectral analysis instead of general FFT to analyze the ice load, which has the characteristics of a random signal. To generate the necessary ice load in the time domain, we must first interpolate the measured data in the frequency domain. Using the Blackman-Tukey method, we estimate the spectrum for the measured data, then process the data to generate the training set required for machine learning. Based on the results, we perform regression analysis by applying four representative techniques, including linear regression, random forest, or neural network, and compare the results with MSE. The deep neural network method performed best, but we provide further discussion for each model.

Welding is the most expensive process in building ships and offshore plants. Therefore, the quantity of welding material should be calculated for the subsections (cells) of the blocks for efficient work planning, and welding paths must be generated for welding automation. Three-dimensional (3D) computer-aided design (CAD) models have been used for this work. However, relevant information regarding welding is often omitted, and a separate database and interface to this database must be developed. In this study, a method of lightweight model-based weld line generation is proposed, followed by the calculation of bead length for welding material quantity estimation and welding path generation. Experiments were performed on various test cases of curved parts and blocks. The proposed method accurately generated weld lines, calculated bead length, and generated welding paths in a short time of approximately 1 s.

The drill floor of an offshore drilling facility is equipped with a collision avoidance system to prevent collisions between moving equipment. In this paper, we present the visualization of the collision avoidance system using the digital twin concept. By classifying the core technologies of the digital twin, the elements necessary for the visualization of the collision avoidance system are derived, and the information for visualization is organized. We conduct 3D visualization of equipment and design IO devices necessary for the visualization. The movement of the floater is considered, and a database is built to efficiently search for the information required for the retrieval of stored 3D information. A collision detection situation is generated by operating the equipment using the input device required for simulation. Collision information is displayed as designed, and it is confirmed that the switching of the display between the present and past time is operating normally. The entire system functions normally as designed, including the input/output with other databases and equipment operation. Implementing a digital twin for an offshore platform is a time-consuming and costly process. It is expected that the improved anti-collision system can be expanded for the digital twin of an entire offshore platform.

In this study, the coupled motion of a mooring system and multifloating cranes were analyzed. For the motion analysis, the combined equations of motions of the mooring line and multifloating cranes were introduced. The multibody equations for floating cranes were derived from the equations of motion. The finite element method (FEM) was used to derive equations to solve the stretchable catenary problem of the mooring line. To verify the function of mooring simulator, calculation results were compared with commercial mooring software. To validate the analysis results, we conducted an experimental test for offshore operation using two floating crane models scaled to 1:40. Two floating crane models and a pile model were established for operation of uprighting flare towers. During the model test, the motion of the floating cranes and tensions of the mooring lines were measured. Through the model test, the accuracy of the mooring analysis program developed in this study was verified. Therefore, if this mooring analysis program is used, it will be possible to perform a mooring analysis simulation at the same time as a maritime work simulation.