Research On The Key Technologies Of Launch Barge's Real-time Stowage Planning

The launch barge is a highly-efficient tool to launch and carry ship products and it can reduce the demand to the dry dock and building berth of a shipyard greatly for today's prosperous shipbuilding industry. The weight of the launched products increases a lot with the development of shipbuilding mode and increasing of the ship tonnage. To ensure the whole launching process completed stably, safely and quickly is worthy of investigation for the launch barge. In this paper, the determination of real-time stowage planning, the calculating method about the loads of ship products and the choice about valve open time of ballast tanks are studied deeply in the launching process respectively.Special and proper floating conditions of the barge need to be remained in the whole launching process all the while. And the floatation is adjusted by changing the water volume of each ballast tank. When, where and how much water needs to be adjusted are the key factors influencing the whole launching process. Usually this process is completed manually which is of low efficiency and complex operation. In this paper, firstly by analyzing mechenics characteristics of the barge, a static equilibrium equations model is established. And it is solved by Newton iteration method on the least adjusted water criteria in which the idea that derivative is replaced with difference quotient is involved in calculating each item of Jacobi matrix. For those barges which subvision has obvious orderly ranks, four special solving methods are studied to the model, and through an example's analysis, these four methods' characteristics are shown and concluded. Then the real-time stowage optimization model is established combined with the characteristic of load-out time as short as possible. It is constraint of static equilibrium equations and the upper and lower limits of the water quantity, and its objective function is determined as the absolute value of the adjusting water. Penalty function method and multiplier method are adopted as to the nonlinear characteristic of the optimization model and normalization processing is applied meantime. The results of the practical examples prove the correctness and applicability of the two models and corresponding solving method. And at the same time the advantages and disadvantages between them are pointed out. That is, the former model is suitable to the case that the barge subvision is symmetrically, and it is of fast calculation speed and stable results, while the latter model is better to the barge subvision with strong arbitrariness. Although the calculation speed is slower slightly, the optimization model has good adaptability and more reasonable load-out results.The pressure exerted onto the barge by the transferring object needs to be determined real-timely in the load-out process in order to provide necessary data for calculation of the stowage model, and its calculation is closely related to the transferring mode. This paper mainly discussed the calculation method under two modes transferring by slideway and gasbags. As to the slideway mode, directional integral method to weight load of the project on the barge, elastic foundation beam method and finite element method with elastic support are analyzed respectively. The examples show that directional integral method is adapted to the case that the support slideway covers the whole object transferring length because of its simplicity, speedness and result close to the practice, and elastic foundation beam method having advantage of high precision should be adopted if there is a large cantilever end between the object and supporting slideway although its formula are very complex. The finite element method is suitable for all cases and of high precision, but it doesn't satisfy the demand of real-time calculation because of participation of other software. To the gasbag mode, the pressure is related to both real-time pressure of each gasbag and number and position of those gasbags on the barge supporting the object closely. Firstly, the real-time calculation of each gasbag pressure is derived according to static equilibrium principle with some proper assumptions. Secondly, the relative movement relation between the gasbag and object is analyzed in terms of kinematics principle, and the calculation formulas of gasbags number and corresponding coordinate are given for different transferring length. Finally, the calculation formula of pressure onto the barge from the gasbags can be obtained through the resultant force calculation and coordinate transformation of corresponding gasbags. The example results demonstrate that the loads onto the barge from the object have three characteristics of discreteness, mutagenicity and periodicity under the gasbag transferring mode. So the slideway mode method shouldn't be used to calculate approximately in this case.How to control the valve open time is of significance to ensure the barge being desirable floatation in the load-out process after the stowage planning determined. Usually, there are two different working modes in the operation of the valves, and the barge floatation in the process will be influenced by the valve open time for both modes. The determination of valve open time is closely related to the object movement velocity, the flux of the ballast tank and the variation in tidal level. Analyzing the characteristics of the water adjusting process, a proper function for characterizing the barge floatation is chosen as objective function, the range of adjusting time is regarded as constraint condition, thus an optimization model on valve open time for ballast tanks of the launch barge can be built, and penalty function method, grid method and simulated annealing method are adopted to solve this model. The example results demonstrate that the optimization model is effective and all the methods are well to maintain good barge floatation in the adjusting process. But the calculated amount of grid method will increase rapidly with the increasing of the number of ballast tanks adjusted or the number of adjusting time's division, and it maybe lead to an unacceptable solution time. Although penalty function method has advantage of short solution time, the barge floatation is not good enough relatively during the adjusting process. While the barge floatation will be the best if simulated annealing method is adopted and just the computing time is slightly longer. So it can draw the conclusion that penalty function method can be used under the case of computing time demanded shortly and floatation limited loosely, and vice versa, grid method or simulated annealing should be adopted.