Research On The Measurement And Evaluation Method Of Curvature Radius Parameters Of Non-holonomic Small Arcs

Non-holonomic small arcs are widely used in the defense technology industry.However,due to their poor integrity and small radius,it is a difficult problem in geometric measurement to measure and evaluate the radius of curvature parameters with high accuracy.In this paper,a non-holonomic small arc measurement device based on the principle of white light interference technology and conoscopic polarization holography technology is used.Aiming at the difficulties in the measurement and evaluation of the curvature radius parameter of the non-holonomic small arc,it is oriented to the measurement method and data processing of the small arc.In-depth research on core issues such as methods and evaluation methods.The main research contents are as follows:(1)It focuses on the mechanism of the non-holonomic small arc measurement device based on white light interference technology and conoscopic polarization holography technology.Then introduces various small arc standard parts used for device calibration.The measurement method of the radius of curvature parameter in this article is determined,and different measurement modes are adopted to obtain the contour point cloud data for the measurement objects of different shapes.(2)The point cloud data processing method of the small arc profile is studied.First,the spatial density denoising method is used to denoise the measured contour data point set.Aiming at the problem of poor fitting stability of the small arc profile data below 60°,a new method based on adaptive cubic exponential smoothing prediction model is proposed to predict and extend the data point set,thereby improving the stability and repeatability of the evaluation.The experimental results show that for the non-holonomic small arc profile data point set with the central angle below 60°,using this method to expand the central angle by about 5° is the best for the evaluation process.And it can improve the accuracy of the evaluation when used with various evaluation algorithms.(3)Firstly,the evaluation simulation analysis of the curvature radius of the incomplete small arc is carried out,and the influence trend of each arc surface parameter on the evaluation process is analyzed.Then the evaluation effect of several commonly used evaluation algorithms is compared.On this basis,an algorithm based on the combination of least squares method and Hough transform method is proposed.First,the rapid calculation of the least square method is used to reduce the quantization range of the arc parameters,and then the Hough transform method is used to search accurately in this parameter space and convert it into an accurate arc curvature radius parameter.Experimental verification results show that the algorithm combines the advantages of the two algorithms.The fast calculation of the least square method reduces the quantization range of the parameters in the Hough transform and greatly improves the calculation efficiency.The Hough transform method can not only ensure the accuracy of the calculation process,but also eliminate the influence of abnormal points on the evaluation process.This algorithm maintains high computational efficiency and strong robustness while having relatively high computational accuracy.It has obvious advantages when comprehensively considering computational precision and computational efficiency.(4)The uncertainty analysis of the non-holonomic small arc measuring device is carried out,and the non-holonomic small arc standard part is used to calibrate the measuring device.The accuracy of this set of non-holonomic small arc measurement and evaluation system is verified by comparing and analyzing the measurement results of contact coordinate machine and optical coordinate machine.