Design Of Two-side Testing Device For Holes Of Solid Wood Board Based On Laser Scanning Technology

In 1990 s,the 3D laser scanning technology began to rise as a new measurement technique.In the process of measurement,the surface of the object is scanned by the laser at the set speed.The 3D point cloud data of the surface of the object is collected.After processing the collected data,3D profile information of the target was obtained.In recent years,3D measurement technology has been developing rapidly,widely used in many fields,such as surveying and mapping,reverse engineering,die design and so on.According to the situation of the research on the surface defects of solid wood plate,it still focuses on 2D detection field and stays in the stage of single surface inspection.Applying the 3D laser scanning technology,a kind of two-side testing system for holes of solid wood board has been designed to obtain 3D point cloud data of solid wood board.However,there is much noise in the original point cloud data acquired by the 3D laser scanner.Also,the density of the point cloud data is high.Therefore,in order to ensure the accuracy,simplicity and speed of the surface reconstruction of point cloud data,it is very necessary to research on pre-process of the original point cloud data.Through the analysis of the characteristics of the data collected from the point cloud,it is identified as the type of the scan line point cloud data.This paper focuses on the smoothing and simplification of the point cloud data,and finally completes the surface reconstruction.It mainly studied the following three aspects:Firstly,A kind of two-side testing system for holes of solid wood board was designed.Based on the understanding of the principle of laser scanning technology,the detection device was designed and built with Chroma + Scan3350 scanner,servo motor,stepper motor,PLC,stroke switch and so on.Secondly,point cloud preprocessing was studied.Based on the analysis of the noise sources of the point cloud data,the noise data were classified and filtered.Several common methods were given to remove the outliers,such as visual inspection method,curve check method and chord deviation method.Several data smoothing methods were analyzed,such as median filtering,mean filtering,gauss filtering,wavelet filtering.Wavelet filtering was selected to smooth the point cloud data,and achieved a great filtering effect.Comparing angle-chord deviation method with curvature sampling streamline method,the latter was finally selected for scanning line data to be simplified.Thirdly,the paper paid attention to the surface reconstruction of the point cloud using NURBS surface reconstruction.The basic principle of NURBS surface reconstruction was given and the process of surface reconstruction was expounded by Matlab.Finally,the surface reconstruction of the point cloud data of the solid wood board was completed and the surface state and hole information of the solid wood board was truly restored.An automatic detection algorithm of boundary points was proposed,which was used to locate the hole and calculate its size.