Research On Main Hull Digital Design And Block Measurement Data Registration Algorithm

The quality of ship design and construction determines ship’s performance, such as safety, economy, functionality, etc. The efficiency of ship design and construction influences the ship development cycle. As the diversification and complication of ships, ship owner’s high demands and fierce enterprise competition, Conventional ship CAD/CAM technologies can’t meet the whole requirements of advanced design and construction and modern construction market. Ship enterprises have to take the competition advantage by improving design and construction efficiency, shortening development cycle, ensuring design and construction quality and reducing construction cost. With the development of computer technology, the digital shipbuilding becomes research hot point in ship industry, and it brings new development mode and technical supports to the ship design and manufacture, and it becomes the digital platform for ship enterprises to support and promote the development of the integration of design and construction of modern shipbuilding mode by digital technologies. The implement of digital shipbuilding has become an important approach for ship enterprises to improve core competence. The starting point of the paper is to improve the efficiency of ship design and the quality of ship construction, shorten ship development cycle by digital technologies.Digital shipbuilding throughout the whole life cycle of shipbuilding, involves a wide range. According to the specific situation and development needs of China’s shipbuilding industry, this paper aimes to achieve rapid ship design and manufacture. In order to reduce working hours, improve equipment efficiency and increase economic efficiency, main hull digital design and block measurement data registration algorithm are studied. The main study contents are as follows.For digital3D main hull design, ship surface design is the base. In the study of hull surface, instead of depending on the conventional prototype, attentions are focus on extracting the design parameters which represent the characteristic of the hull. The energy optimization method is proposed to get the expression of the hull fairness surface with NURBS, using design parameters as the design variables and least sum of curvature square of hull curves and surface as the objective object. The basic shape feature of hull curves can be adjusted under the constraint related to interpolation points, derivative vectors, curvatures, areas and centroid points. In this way, fairness of hull surface is ensured. The hull surface is represented with NURBS, and it can be used in subdivision and structure design.Based on the hull surface, the paper implements subdivision design, a new parametric subdivision of the top-down approach is proposed. The proposed method is based on space subdivision. For this, several parameters (bulkhead positions and folding point positions of the inner bottom) are established to generate the subdivision planes which are used to cut the ship hull. The non-manifold modeling containing set operations is applied to generate compartment solid model. Then link the constrains to the geometric model. Use the constrains to optimize subdivision and get the subdivision scheme which satisfy all constrains, and calculate the hold capacities. This method reduces the complexity of the compartment and intuitively reflects the design thought. The compartment and the calculation of hold capacities can be finished rapidly.Use the hull surface and compartment model as structure design background. Knowledge-based engineering quick design method for hull structure is put forward, which combines with parametric technology. The concept of knowledge ontology for hull structure is introduced. And establishment of knowledge base for hull structure design is discussed to achieve3D quick optimizing design. During the design, positions of structural members are driven by position parameters. Scantlings of structural members are obtained by Rule-Based Reasoning and Case-Based Reasoning. Main structures are optimized by quantum-behaved genetic algorithm. This method achieves knowledge reuse and accumulation, provides design results inspection. So that reliable ship structure is quickly obtained. The created3D structure model can be used as the life-cycle digital model. It also can be used in the phase of accuracy construction.Based on ship digital model, the paper studies on key technologies of digital accuracy shipbuilding, is focusing on quick measuring analysis technology for hull blocks and quick simulation erection technology. Quick measuring analysis for hull blocks is an important step in the accuracy shipbuilding. Hull block construction data can be rapidly and precisely measured by total station. Compared the measuring points with design points of3D model in3D visualization environment, it is a hull block measuring analysis mode adopted by digital accuracy shipbuilding. In the paper, rough matching adopts PCA algorithm and the pair-wise points are matched by searching minimum distance. Initialized by the former result based on rough matching, refined matching that adopts Euler theory leads to perfect matching by translating and rotating the measured points. The proposed algorithm can automatically match measurement data with CAD model without prior information on transformation, and evaluates construction precision of hull blocks accurately, and provides an instructive basis for subsequent simulation erection. In the study of quick simulation erection, an automatically rapid positioning method is proposed for erection block achieving reasonable position. The error distribution at different directions is determined by using weight vector. The best positioning result and reasonable scheme are achieved by adopting nonlinear multi-objective optimization by introducing the erection engineering constraints (e.g. levelness, verticality and flatness) into the objective function of the computing model. The scheme accords with the actual engineering and it’s easy to realize thus shorts the erection time.In conclusion, main hull digital design and block measurement data registration algorithm of digital shipbuilding are studied in this paper and corresponding methods are offered including rapid ship form design, compartment subdivision, structure design, measuring analysis and simulation erection, aiming at helping digital rapid shipbuilding theory development, shortening ship development cycle, improving quality and efficiency for shipbuilding and being helpful to practical engineering application.