Development Of Portable Detection System For Frame Lines Of Hull Plate Based On Line Structured Light 3D Vision

The forming of hull plate is an important part of the whole hull construction.Although the forming process of hull plate is mostly automated,the accuracy of single curvature plate with the largest amount and plate with small longitudinal inclination in hull construction is still detected by triangle template or adjustable form-checking template.Its low detection accuracy,low efficiency and high cost greatly affect the quality and speed of ship construction.Therefore,this dissertation aims at the requirements of high-efficiency and high-quality frame lines of hull plate detection.A portable detection system for frame lines of hull plate based on line structured light 3D vision is developed.The research focuses on the design of detection system scheme,preprocessing and feature recognition of light stripe image,theoretical data acquisition,calibration technology,point cloud registration,light center extraction and deviation calculation.Aiming at the characteristics of long frame lines,large curvature and high forming accuracy,a portable linear structured light 3D vision detection scheme for frame lines of hull plate detection is proposed.The measurement device of the detection system is designed and optimized in detail.The baseline distance of the measurement device is240 mm and the baseline angle is 56°.Through the hardware selection and system construction,the hardware system of the portable detection equipment for frame lines is established.Research on the key technology of 3D vision measurement of line structured light:Aiming at the problem that there are many processing marks on the surface of the hull plate,and the collected image has a lot of noise,which affects the recognition of the line stripe of frame line,an intelligent recognition algorithm of the frame line laser stripe is proposed,which realizes the accurate recognition and feedback of the line stripe of frame line.Aiming at the problem that the traditional light center extraction algorithm cannot realize the accurate light center extraction.A secondary gray barycenter center extraction algorithm based on normal curve is proposed.Sub-pixel extraction of light stripe center is realized.The extraction accuracy and operation efficiency of the algorithm are analyzed.The results show that this method is better than the gray center extraction algorithm.The extraction error is reduced by 32.9 % and the operation efficiency is high.Aiming at the difficult problem of large scene calibration in the system.Zhang camera calibration method and optical plane calibration method based on moving target are used.The high precision calibration of the measurement system is realized.The measurement point cloud of the frame line is successfully obtained,and the three-dimensional reconstruction is realized.Research on point cloud registration and deviation calculation: Extract theoretical data from Tribon ship design system.Point cloud model and surface model are reconstructed.According to the accuracy requirements of point cloud registration,the point cloud data of the frame line is encrypted and reconstructed.According to the characteristics of hull plate bending,a coordinate transformation coarse registration algorithm for automatic identification of feature points is proposed.Provides a good initial position for subsequent point cloud alignment.In order to solve the problem of using ICP algorithm directly to cause part of the measurement point cloud above the theoretical point cloud.A constrained local point cloud ICP fine alignment algorithm is proposed.The precise alignment of two point clouds is realized.Draw lessons from the characteristics of manual inspection process of frame lines of hull plate.A deviation calculation algorithm based on projection interpolation is proposed.The deviation value of each measurement point cloud is obtained.And according to the bending forming process and testing requirements.The corresponding process guidance was proposed.Portable detection system for frame lines of hull plate is developed: The portable detection system of frame lines of hull plate is developed.The developed portable detection system is used to measure standard blocks for many times.The measurement error of the detection system is less than±0.3 mm.Fully meet the accuracy requirements of detection system.Finally,the detection system was used in the hull plate processing workshop.The results show that the single detection time of the detection system is about 10 s,and the maximum detection frame line length is 2100 mm,which can fully meet the needs of field detection.This system realizes the efficient,green,portable,large-scene,low-cost,precise,digital and intelligent detection of frame lines of hull plate.