Deep Tube Inner Diameter Measurement Based On Optical Tracking Method

Deep-hole parts,such as artillery body tubes,sleeves,hydraulic cylinders,etc.,are widely used in the defense industry,aerospace,automotive and other fields.Such workpieces not only require strict control of tolerances during machining,but also require timely detection of damage incurred during use.Whether from the perspective of detecting whether the precision parts are qualified or ensuring the performance of the equipment,the measurement of geometric parameters inside the deep tube is of great significance.The existing contact deep tube internal diameter measurement and non-contact body tube internal diameter measurement in the centering requirements are high,for the longer body tube coaxiality error generated by the impact of correction difficulties.In this paper,based on the optical tracking principle and the dispersive confocal technology,the non-contact measurement system of deep tube internal diameter is studied for the problems of traditional internal diameter measurement which requires strict centering and the large size of the probe which is difficult to adapt to small diameter,the main research contents are as follows:(1)The technical characteristics of deep tube type workpiece measurement are analyzed.Taking the tracking measurement technology as the starting point,the dispersive confocal ranging technology is applied,and the measurement method of laser scanning the surface of the measured part is used to obtain the internal diameter point cloud data.The point cloud data is calculated based on the conversion relationship between the absolute coordinate system and the measurement coordinate system,and the internal diameter geometry of the measured part is obtained.The designed measurement system can be used to measure the internal geometry of the inner diameter larger than 45 mm.(2)The influence of eccentricity and tilt on the measurement results between the probe and the deep tube-type workpiece during measurement is analyzed.The least squares fitting method is used to calculate the inner diameter of the measured part in the single section inner diameter measurement method;for the overall inner diameter dimension of the body tube,the optical tracking technology is used to obtain the measurement section circle center,and the eccentricity and tilt compensation parameters are inferred by the deviation of the virtual axis from the theoretical value in the Jedi coordinate system to improve the measurement accuracy.(3)The mechanical structure and optical system of the measuring device are designed and simulated,and the process of data acquisition is described.By installing the probe axially with a 45° folded optical path,the problem that the sensor is long and cannot be directly incident on the inner surface to measure the body tube diameter dimension is solved,and on this basis,the applicable diameter range is expanded by offsetting the probe position by the vertical axis.(4)design tilt simulation experiments to verify the mathematical model;build a deep tube internal diameter measurement system experimental platform,simulating a 50 mm caliber deep tube to the internal diameter measurement system involved in the internal diameter measurement experimental results show that its absolute measurement error is better than ± 10μm,the range to 5mm.