Research On Shipbuilding Accuracy And Assembly Analysis With Engineering Constraints

Because the size of hull block is gigantic,it is easy to accumulate errors in the construction process.Therefore,how to improve the hull construction accuracy and reduce the construction cost has become an important research content of scholars in the field of ship engineering at home and abroad.Based on the shortcomings of the current points matching algorithm for hull blocks and the characteristics of ship engineering,this paper has studied the key technologies related to shipbuilding accuracy control,such as the method of automatically finding and eliminating wrong measurement points,the method of measuring and analyzing hull blocks considering engineering constraints and the intelligent generation method of assembly scheme for hull blocks,and then developed an integrated system of shipbuilding accuracy analysis and assembling with engineering constraints.The specific research contents are as follows:An improved Random Sampling Consistency(RANSAC)algorithm is proposed to prevent a few error points caused by surveyors,such as mismatched point pairs and outliers.In order to improve the standard RANSAC algorithm effectively,the improved algorithm should not only be used in shipbuilding industry,but also improve the accuracy and speed of the algorithm.Firstly,some error points are eliminated in advance by using effective constraints,which reduces the number of iterations and improves the speed of the algorithm.Secondly,the Singular Value Decomposition(SVD)method is used to solve the transformation parameters,and the reasonable threshold is set to verify and mark outliers.Finally,after the iteration,the outliers are removed accurately,and the maximum consistent point set is obtained,which improves the accuracy of the algorithm.The eliminated measurement point set and design point set are applied to the subsequent measuring and analyzing hull blocks with engineering constraints.Based on the more accurate measurement point set and the design point set for hull blocks,a point set matching method based on the improved coherent point drift(CPD)algorithm and considering various engineering constraints is proposed.Firstly,the improved CPD algorithm is used to obtain more accurate initial matching values,compared with SVD method.Then,the weights of engineering constraints are automatically obtained by Analytic Hierarchy Process(AHP),and then the weight vector is introduced into the multi-optimization objective function to solve the more reasonable matching results.The point set matching method is mainly applied in accuracy measurement analysis and fast simulation assembly analysis for hull blocks.In the accuracy measurement analysis for hull blocks,this method can match measurement points obtained by total station with design points.The more reasonable analysis results can be obtained when the accuracy requirements of hull blocks in different directions and various complex engineering constraints(such as verticality,levelness,flatness and symmetry)are satisfied,which provides the basis for the subsequent assembly of hull blocks.In fast simulation assembly analysis for hull blocks,the assembly constraints(such as straightness and hard point constraints)are introduced into the multi-objective optimization function in this method,and then the non-linear optimization function is solved to obtain the optimal loading results,which provides the most reasonable assembly scheme.It shortens the occupancy time of equipment used in building hull,reduces the workload of staff,and thus improves the construction efficiency and quality.Based on the research of key technologies related to accuracy control of hull blocks,an integrated system of shipbuilding accuracy analysis and assembly with engineering constraints is developed in this paper.The functions of engineering constraints analysis module and automatic searching and eliminating error measurement points are added to realize the automation and intellectualization of shipbuilding accuracy analysis and assembling.