Study On Characteristic Parametric Design Of Ship Hull Surface Technology

Ship design is a complex subject which has a strong integrity. It is the key link of the cycle of shipbuilding. The level and capability of ship design have a very significant impact on fabricating cost, production efficiency and competitiveness of product. Research and Development of modern ships develop towards digitization, the primary task of digital shipbuilding is to achieve digital ship design, and parametric design of ship is one of the significant research contents of digital ship design.The method of parametric design is based on the mathematic formulation of surface and the solving of optimization problem. International Organization for Standardization (ISO) promulgated International Standard STEP (Standard for the Exchange of Product model data) about Industrial Product Data Interchange, when NURBS technique haven’t developed maturely, stipulate NURBS the only mathematical method to define the geometry of industrial products. With the rapid development of NURBS and its supporting technologies in recent years, the ship hull is expressed by NURBS method one after another. The design of molded lines turns to the NURBS modeling, too. The solving of optimization problem is another core content of parametric design, there are various ways to solve optimization problem, it is therefore quite necessary to choose an appropriate method to solve it. The guiding ideology of parametric design is to generate the ship hull by using a small quantity of parameters. Construction the parametric mathematical model of ship curve and surface and the method of solving of it, which is the key research contents of parametric design of ship hull form.Taking account of the fairness criteria, this thesis sets the improved energy target function as the objective function, which considers both the strain energy and curvature transition of the curve and surface. So it ensures the fairness of ship curve and surface. In consideration of that NURBS defines shape by means of control points, so the thesis set the control points of ship curve and surface as the unknown variables for the optimization problem, at the same time, set the geometrical characteristic parameters of ship hull as the constraint conditions, then constitute a nonlinear programming (NLP). In that way, the control points of ship curve and surface can be obtained according to the characteristic parameters which are designated by ship designer and thereby the parameterized ship hull can be modeled in a short time. This thesis adopts the Sequential Quadratic Programming (SQP) algorithm to solve the nonlinear programming. This algorithm ensures the convergence of the optimization problem, furthermore, it increase the accomplished efficiency of the parametric method which solve the numerical calculation and fairing problem effectively.