Measurement Method Of Barrel Twist Rate Based On Panoramic Imaging

The rifling twist rate of barrel plays a crucial role in determining its performance,and high-precision measurement of this parameter has become an increasingly pressing demand.Existing methods for measuring rifling twist rate face significant limitations,particularly for smaller-diameter barrels,and suffer from limitations in accuracy,extended measurement times,and complex operating procedures.In recent years,high-resolution,broad field-of-view panoramic imaging equipment has the advantage of circumferential360? imaging and is extensively employed in pipeline inspection,3D reconstruction,and other fields.At present,there is a dearth of domestic research literature regarding the measurement of rifling twist rate in smaller-diameter barrels using panoramic imaging technology.The paper proposes a method based on panoramic imaging for measuring the barrel rifling twist rate,and the main research contents are as follows:1)A panoramic imaging model of the barrel,accounting for multiple sources of error,including rotation and translation,was established based on the three-dimensional spatial relationship between the barrel and the imaging system.The equation for calculating the panoramic imaging rifling twist rate was derived accordingly,and the factors affecting the measurement accuracy are analyzed through simulation.2)A barrel rifling twist rate measuring system based on panoramic imaging has been developed,which primarily consists of an endoscope for panoramic imaging,an actuator,a ring light source,and a rope displacement sensor.By operating the actuator,the panoramic imaging endoscope device captures panoramic images of the inner wall of the barrel in various axial locations,the ring light source effectively enhances the contrast between the yin and yang rifling patterns in the barrel,and the rope displacement sensor records the axial distance.3)Focusing on developing the algorithm on panoramic imaging for measuring the barrel rifling twist rate.We started by employing camera calibration and perspective transformation calibration algorithms to correct the distortion of the panoramic images of the barrel.We then enhance the features of the corrected images using the polar coordinate panoramic image enhancement algorithm.To track and locate the target rifling pattern in real-time among the background of multiple rifling patterns and enable us to obtain the rotation angle of the rifling patterns,we propose an automatic tracking and positioning algorithm for the rifling patterns,and calculate the rifling twist rate of the barrel accurately tube based on the rotation angle and axial distance.The calibration experiment and the actual measurement test of the rifling twist rate of the barrel provide two independent confirmations of the validity and accuracy of the proposed method.The accuracy calibration experiment is based on the calibration tube,and the experimental results and data obtained from the calibration tube demonstrate the maximum rifling twist rate measurement error of less than 2?,satisfying the criteria for actual measurement.At the same time,the multi-caliber body tube serves as the target for the actual measurement test,and the obtained results and data indicate that the maximum rifling twist rate measurement error of the measurement system is less than 3?,with the result error of less than 1?.The proposed measurement method of barrel twist rate based on panoramic imaging is highly accurate and effective,providing a digital measurement that increases accuracy while decreasing labor intensity and shortening the measurement cycle.