Study On Key Technologies Of Comprehensive Automatic Processing For Line Heating

The mass hull plate surfaces belong to non-developable surfaces. The fabrication ofdouble-curved hull plate surface has become the bottle-neck in whole shipbuilding productionsystem. At present, line heating is the main method to build such hull plate surfaces inshipyards. During the line heating process, the plate surface has to be repeatedly inspectedand reformed to meet the requirement of the designed shape. The traditional manual pattern ofline heating process, which is relied on workers' experiences can not meet the need of modernshipbuilding. Therefore, a comprehensive automatic line heating process increasinglydevelops into an active research topic. The key technologies in the automatic processingsystem have been investigated in this paper, which are introduced as follows:(1) The surface fitting for deformable plate after line heating processThe expression of deformable plate has been investigated during line heating process. Byutilizing the method of bicubic-spline interpolation function, the plate surface after lineheating process has been fitted with the given discrete data in the different boundary condition.By combining the visual interface of VC program with the powerful numerical computationand graphics display of MATLAB, the computer software of the surface fitting fordeformable plate after line heating process has been developed.(2) The surface fairing for the deformable plate after line heating processThe fairing for surface edge of deformable plate after line heating process has beenresearched. Based on the algorithm for B-spline curve fairing with constraints and the fairprinciple for B-spline surface, a new fairing algorithm has been presented with constraints forB-spline surfaces. The new algorithm constrains the perturbation range of the control pointsand the shape variation of the curve, and can solve the problem of boundary data error in thesurface fitting for deformable plate. Numerical results show that the accuracy required inactually line heating can be satisfied by applying this method into the surface fitting for thedeformable plate.(3) The inspection for deformable plate surface after line heating processThe deformable plate surface after line heating process has to be inspected with thedesigned surface. The plate coordinate can be built up by utilizing the property of differentialgeometry. With the utilization of the surface character and the coordinate switch, themeasured plate surface can achieve the best matching with the objective plate surface. A new method of surface inspection for deformable plate after line heating process has beenintroduced based on the algorithm for tabu search. The curvature is used to inspect the formerror of the surface and the matching to designed shape is used to inspect the profile error ofthe surface in this method, which can meet the requirement of surface inspection fordouble-curved plate in line heating process.(4) The precise development of complicated thick plate surfaceThe investigation of the precise development for complicated plate surface has beencarried out to provide the reheating information for unformed plate. By taking the thickness ofplate and angular distortion as input parameters and displacement coefficient of neutral asoutput parameter, BP neural network model has been established. Angular distortion in thedevelopment of thick plate surface can be calculated exactly in the new method. The platesurface can be adaptively divided into regions based on its quasi-rulings and then thetransverse shrinkage of the plate can be calculated. According to the property of the offsetsurface, a new method for surface development has been established to calculate the angulardistortion and the transverse shrinkage simultaneously in plate surface development, whichcan provide guidance to determine the reheating information for unformed plates.