【作者】 孙霄峰；

【导师】 尹勇；

【作者基本信息】 大连海事大学 ， 交通信息工程及控制， 2008， 博士

【摘要】 随着现代渔业的发展,渔船操作模拟器将在渔业教学与培训、渔业海事测评、渔业船舶事故预防安全措施评估、渔业港口规划等方面发挥越来越重要的作用。为在渔船操作模拟器中进行单船中层拖网作业过程的动态仿真,本文提出了一种单船中层拖网系统数学模型的建模方法,开发了单船中层拖网系统的仿真程序,并实现了单船中层拖网作业过程的三维可视化,为渔船操作模拟器的研究与开发打下了一定的基础。本文在以下几个方面做了重点研究:1.提出了一种单船中层拖网系统数学模型的建模方法,并通过场景管理软件OpenGVS(Open Generic Visual System)实现了单船中层拖网作业过程的三维可视化。在建模过程中,将单船中层拖网系统的数学模型分为渔船、拖网曳纲以及网具系统的数学模型,并通过边界条件实现了数学模型之间的耦合,从而可以进行单船中层拖网作业过程中收放网过程的动态仿真。论文的仿真结果验证了所提出建模方法的可行性。2.改进了船舶缆绳张力的计算模型,充分考虑了缆绳的自重和非线性应变。若缆绳的应变满足虎克定律,利用悬链线方程和虎克定律推导出缆绳张力和无应力长度的对应关系,并采用试算法计算缆绳张力;否则,忽略缆绳的自重,通过由缆绳的应变曲线图拟合的多项式来计算缆绳张力。根据计算出的缆绳破断强度对缆绳张力是否超出安全负荷以及缆绳是否破断进行了判断。计算实例验证了模型的正确性和实用性。3.基于船舶操纵性分离建模理论,采用荷兰船模试验水池B系列螺旋桨的敞水试验结果,利用Akima插值获得了不同类型的调距桨在不同螺距比下的四象限推力系数和扭矩系数,求得调距桨的推力和扭矩,建立了调距桨船舶的平面运动数学模型。模型充分考虑了风、流对船舶操纵的影响,可用于调距桨船舶常速域和低速域的操纵运动仿真。仿真研究表明:仿真结果同实船试验结果吻合,本文建立的模型是合理的,能够满足大型船舶操纵模拟器对船舶运动数学模型仿真精度的要求。4.提出了一种网具系统模型的数值解法。利用同某一个质量点相连的其它质量点的已知位移代替其实际位移来求解该质量点所受到的弹性力,从而可进行每个质量点方程的单独求解,避免了直接求解巨大的非线性微分方程组,减少了计算时间。采用隐式Newmark-β方法以及牛顿迭代法对每一质量点的运动方程进行单独求解,增大了模型可稳定求解的时间步长。5.利用有限差分法建立了拖网曳纲的三维水动力模型。通过欧拉角的转换关系获得了曳纲微元段矢量动力平衡方程在曳纲局部坐标系下的方程组形式;在建模过程中,将网板视为曳纲的尾部节点,根据达朗伯原理建立了网板的平衡方程,并将其作为曳纲模型的尾部边界条件。通过在时间和空间上对拖网曳纲平衡方程组进行中心差分以及首尾边界条件的处理,将该方程组转换为定解代数方程组,并采用牛顿迭代法求解。模型考虑了均匀流以及曳纲的收放速度对曳纲张力和形状的影响,能够用于拖网曳纲非定常运动的模拟。对有关文献提出的模型缆进行了仿真计算,并将仿真结果同该文献的计算结果进行间接比较,验证了模型的有效性。6.利用集中质量法建立了网具系统的数学模型,将网具系统离散为通过无质量弹簧连接的质量点的集合,根据牛顿第二定律建立了质量点的动力学方程,并考虑了均匀流对网具系统运动的影响。分别对单一网片和中层拖网的运动进行了动态仿真,并将仿真结果同水池试验结果进行了比较,从而验证了模型的合理性。更多还原

【Abstract】 With the development of modem fishery, fishing simulator will play a more and more important role in the fishery education and training, fishery maritime evaluation, assessment for preventing fishing ship accidents and fishing port planning, etc. To simulate the dynamic behaviors of single-boat mid-water trawl system in fishing simulator, a modeling method to establish the mathematical model of single-boat mid-water trawl system is proposed. Also, simulation software is developed and visualization of the system is realized, which lay a good foundation for the development of fishing simulator. The primary research and contributions of this dissertation summarized here are:1. A modeling method to establish the mathematical model of single-boat mid-water trawl system is proposed, and visualization of the system is realized by using scene management software OpenGVS (Open Generic Visual System) . The mathematical model of the system is divided into mathematical models of trawler, warp and fishing net, which are connected by boundary conditions reflecting the influence of each other. By using this modeling method, the dynamic simulation of the process of drawing in and giving out the fishing net is realized. The feasibility of proposed modeling method is verified by simulation results.2. Considering mooring line weight and non-linear elongation, the mathematical model for calculating mooring line tension is improved. When the line elongation obeys Hooke’s law, the relationship between line’s tension and original length is induced by using catenary equation and Hooke’s law, and the line tension is obtained through trial. Otherwise, the line weight is neglected and the line tension is calculated by using the polynomial obtained through line stress-strain curve. Whether line tension exceeds safety load and line is broken or not is judged by calculatied line broken intensity. The correctness and practicability of the model are verified by computation instances. 3. A maneuvering mathematical model for Controllable-Pitch Propeller (CPP) ships with three degrees of freedom is established according to separate modeling theory. Based on Netherlands Ship Model Basin’s open-water tests, CPP thrust coefficients and torque coefficients in four-quadrant with different pitch ratio of screw and different types of CPP are obtained by using Akima interpolation. Therefore, CPP thrusts and torques are obtained. With the influences of wind and current, the model can be used for maneuvering simulation of ships equipped with CPP in ordinary-speed and low-speed fields. Simulation results being similar to the sea-trial test shows that the model is reasonable and its precision can meet the requirement of full mission ship-handling simulator.4. A numerical calculation method for the mathematical model of fishing nets is proposed. Instituting variables of position of mass points of calculated positions to calculate connected mass points’ elastic force, equations of mass point can be solely calculated. This method can avoid solving the huge nonlinear equations directly, and computing time can be reduced. Also, Newmark-βintegration method is used to calculate the equations of mass point, which can stably take large time steps.5. The dynamic model of warp is established by using finite difference method. The equilibrium equations under local coordinate are obtained through Euler angle transformation. In the modeling of warp, otter door is treated as the end node. The equilibrium equation of otter door is established through d’Alembert’s principle. It provides the end boundary condition of the dynamic model of warp. By central difference in time and space and boundary conditions, equilibrium equations of warp are transformed into the definite equations and solved by Newton’s iteration. The model also takes into account influences of uniform current and winch speed of warp, and can be used to simulate unsteady warp motions. Simulation computations of a model towed cable proposed in a paper have been done. Comparing the computation results with that given in the paper, the rationality of the model is verified.6. A hydrodynamic model of fishing net is established according to the lumped mass model, which divides fishing net into finite mass points connected with springs without mass. According to Newton’s Second Law, equation of mass point is set up tak- ing the influence of uniform current into account. Dynamic behaviors of a panel net and a mid-water trawl are simulated. Comparing the computation results with that of flume experiments, the rationality of the model is verified.更多还原