| The floating crane is an important offshore support equipment,which can be used in large-scale marine projects such as marine rescue and salvage projects,offshore wind power installation and deep sea operations.As floating cranes becoming large-scale,automated and intelligent,efficient and automatic ballast system has become an urgent need.Based on analyzing the operational characteristics of the lifting process in large-scale revolving floating cranes,this paper established an optimization model and efficient solution algorithm for ballast water dynamic allocation based on pump system in revolving floating cranes.Besides,the test platform of the automatic ballast system for revolving floating crane is established.The main research contents are as follows:(1)Based on analyzing of the working principle and operation flow of the ballast system,the hydrostatics of ships and optimal theories,the optimization model of ballast water allocation is built to minimize the ballasting time of floating cranes.In this model,the variations of water height levels and IFBWM(Initially Filling Ballast Water Mass)in all ballast tanks are taken as the variables and the hull balance in the ballasting process is taken as the constraint conditions.Thus,an optimization model of ballast water efficient allocation in revolving floating cranes is done,which can provide theoretical model support for ballast water allocation optimization and its computer aided design.(2)A ballast water allocation solving model based on dynamic programming(DP)is proposed.Based on the lifting process and rotation angle,the ballasting process is divided into several stages for solving.The optimal ballast scheme of the whole lifting process is obtained,and the algorithm flow is given.The analysis of a numerical calculation case of lifting a 300 t cargo shows that the optimal ballast scheme can reduce the ballasting time and allocation mass by 11.22%and 11.19%compared with the experience scheme.During the rotation of the crane,the ballast water height level of each tank changes in a trigonometric function.The sensitivity analysis of the factors affecting the allocation shows that the optimal ballasting time can be obtained by selecting the appropriate IFBWM,and carrying out preloading can reduce the amount of ballast water during the loading process.(3)Aiming at the problems that the conventional dynamic programming has low computational efficiency and the optimization scheme is difficult to be practical,this paper proposes improved DP solution algorithms,by changing the threshold of the optimization variable,the interval of DP and reducing the number of used ballast tanks.The case study shows that when the threshold variation is less than 0.4,reducing the threshold can reduce the calculating time;when the stage interval of DP is set to(2,10),the calculating time can be greatly reduced and a better allocation scheme can be obtained.The load adjusting capacity of different ballast water tank is various.Selecting the most sensitive ballast water tank for lifting cargo can reduce the number of ballast tanks involved in the transfer,and obtain the more practical transfer scheme.(4)In this paper,the automatic ballast system design scheme based on PLC is proposed,and an experimental platform for ballast water transfer based on scale model is developed.The test results show that the maximum heel angle of the ship without ballasting is about 15°,and the heel angle of the optimization scheme is within 2°.The validity of the model and the algorithm is verified.The design of the ballast system is feasible.This paper can provide a theoretical and technical support for the revolving floating crane to select a suitable ballast scheme during the hoisting process,establish an efficient automatic ballast system,achieve the dynamic ballast control by computer,improve the construction efficiency of the floating crane,and reduce the energy consumption. |
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