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| Abstract | The block erection operations in the shipyards generally include block lifting, transporting, turnover, and lowering procedure. During the operation, there are potential risks such as interferences with wire ropes, overweight, collision, which can lead to severe accidents. To check such risks in advance, the physics-based simulations are often required before the actual operation. For this, detailed modeling of the equipment and the operation is necessary to reflect the real situation accurately, which is impossible with conventional modeling methods. Meanwhile, in the actual operation, the position and the orientation of the block should also be precisely controlled to avoid any risks. However, the actual operations are performed manually by the operator, and the cranes used for the erection of the block consist of sophisticated equipment, which makes them difficult to control. In this study, the detailed modeling of the operation situation and the equipment are introduced for accurate simulation. Then, the control method of the crane is suggested for reliable and efficient control. Firstly, the block turnover operation by one floating crane and two crawler cranes is modeled considering the interferences between wire ropes and the block. For this, the interaction model between wire rope and the block, including contact and friction, is suggested. Then, the contact forces exerted on the block are calculated. Secondly, the block lifting by the floating crane is analyzed considering the coupling motion of the floating crane and the mooring system. The interaction among the floating crane, the mooring line, and the seabed is introduced under the various sea condition. Lastly, the control of the gantry crane and the floating crane is performed for block lifting, transporting, and turnover operation. As the gantry crane and the floating crane consist of complicated equipment such as trolleys, booms, equalizers, and wire ropes, the control theory of the underactuated mechanical system is adopted. For the verification, the comparison of the suggested interference model and the analytic solution is conducted. As the proposed model has been divided into three; contact model, friction model, and sliding model, each model is verified independently. Then, for the verification of the suggested mooring line model, the tension and the deflection of the mooring line are compared with that of the commercial software, OrcaFlex. The convergence test was also performed according to the number of the element, to find a proper number of the element of the mooring line. Lastly, the inverse dynamics model formulated in this study is verified by applying it to the dynamic model of gantry crane and check if the block tracks the desired trajectory. To evaluate the effectiveness and applicability of the proposed methods, they were applied to the dynamic analysis of various kinds of block erection operations by using cranes. Three representative applications are provided, such as block turnover operation by floating crane and crawler cranes, block lifting operation by floating crane, and block erection operation by gantry crane and a floating crane. As a result, the proposed method could reflect the actual operation situation accurately, and the block was controlled to the desired trajectory. We conclude that the developed simulation and control methods are applicable to actual operation in ships and offshore structures. |
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| Publication Date | 2020-02-26 |
Hye-Won Lee, "Wire Rope Contact Model and Crane Control Method for the Advanced Simulation and Automation of Block Erection", Ph.D. Thesis, Seoul National University, 2020.02.26
이혜원, "블록 탑재 자동화 및 시뮬레이션 고도화를 위한 와이어 로프 접촉 모델 및 크레인 제어 방법", 박사학위논문, 서울대학교, 2020.02.26
