Research On Measurement Of Geometric Parameters Of Bullet Profile Based On Machine Vision

Geometric parameters of bullet shape are one of the main factors to evaluate the quality of bullet production,and they are also important factors affecting shooting accuracy.In view of the fact that the traditional measurement of geometric parameters of projectile shape mainly relied on manual measurement of gauges,the efficiency was relatively low.With the rapid development of China’s military industry,it is urgent to detect geometric parameters of bullet shape efficiently and accurately.In this paper,non-contact measurement and modern digital image processing are used to process projection image of bullet.Finally,the number of pixels is converted into actual geometric parameters of bullet shape,so that accurate,stable and efficient measurement could be achieved.Firstly,according to the characteristics of the geometric parameters of the projectile shape to be tested,the overall design of the detection system and the selection of devices are carried out.Secondly,the monitoring system is built and the calibration principle of the system is briefly analyzed.Then the projection image of the collected projectile is preprocessed to eliminate the interference noise and enhance the target image.Canny operator is used to extract the whole pixel edge,and then the improved Sobel template is used to extract the sub-pixel edge of bullets by comparing three sub-pixel algorithms.Then on this basis,Tomasi-Shi sub-pixel focus detection is used to extract corner points,and Hough transform is used to extract the ground straight line to obtain the geometric parameters of the relevant straight line segment;through the general equation of the circle,the least squares method is used to solve the overdetermined equations to solve the arc radius of the warhead;by calculating the central axis of the warhead and the shell respectively,the inclination of thewarhead shell is calculated by using the formula of the angle between the two lines.After the actual calibration of the system,the actual measurement of the above three parameters of 12.7mm bullet is completed.The experimental results show that the system calibration effectively improves the measurement accuracy of the system.The relative error of the linear parameters of 12.7mm bullet with small size is-0.1%,and the maximum absolute error is 0.009mm;the relative error of the linear parameters of larger size is-0.03%,and the maximum absolute error is 0.023 mm.The relative error of the arc radius is 0.16%,and the maximum absolute error is 0.257 mm.Considering the approximate treatment of the arc edge,the error is too large.The warhead shell inclination is measured by the two-dimensional dimension measuring instrument of Keynes,the maximum deviation is 0.07 degrees,and the measurement results have no significant difference,which meets the accuracy requirements.