Research On 3D Point Cloud Digital Value Transfer Method Of End Frame Drilling Jig Model

In the process of value transmission and traceability,the end frame drilling jig used in aerospace and military industry still remains in the conventional mode of step-by-step transfer of physical standards.Due to its own limitations such as the huge size,the long transfer routes,the easy wear and tear of physical quantity transmission,the low verification efficiency,it is urgent to adopt a new digital value transmission method to change the traditional mode.This paper will take the end frame drilling jig as the research object,establish a digital standard model,carry out the corresponding model accuracy evaluation and study the digital feasibility method of quantity value transfer.The main work is carried out around the following contents:（1）On the basis of the traditional value transfer,the digital value transfer route of drilling jig is proposed according to the geometric measurement characteristics of the end frame drilling jig,and the digital benchmark is defined.The model local adaptive subdivision algorithm combined with the dihedral angle and the improved 3^1/2 subdivision algorithm improves the accuracy of the model conversion to the STL output format.（2）The 3D point cloud data of the drilling jig is obtained,the scattered data is divided into neighborhoods and normal information is estimated.By analyzing the neighborhood of the 3D point cloud,k neighborhood search method is proposed based on an adaptive space sphere.The least squares method is used to fit the points cloud surface equation to calculate the corresponding normal vector and curvature,which lays the foundation for the subsequent point cloud processing flow.（3）The drilling jig of the 3D point cloud is denoised,simplified and reconstructed to obtain the digital model.The paper uses statistical analysis combined with bilateral filtering to remove or smooth noise points,uses the curvature as a threshold to determine whether the sampling points are retained,and finally optimize the rotating ball reconstruction algorithm to improve the adaptability of the algorithm.At the same time,the geometric topology of the model reconstructed by this algorithm of the structure is more in line with the original model.（4）In this paper,the error analysis of the digital value transfer of the drilling jig is carried out,combined with the theoretical research on the evaluation of the 3D reconstruction model.It is proposed to evaluate from two perspectives of quantization error and non-quantization error.The quantitative evaluation analyzes the error source of the overall process of digital value transfer and accurately calculate the corresponding error size.Non-quantitative evaluation comprehensively considers the factors of model quality,hole book,three-dimensional error of sampling point and error distribution,analyzes the cause of error and proposes specific improvement measures.