An advanced multi-camera system for automatic, high-precision and efficient tube profile measurement

In this paper, an advanced multi-camera system based on stereo vision is developed for automatic, highly accurate and efficient tube three-dimensional profile measurement of tubes, which can be applied to tube pre-assembly or in-process tube profile inspection. Multiple cameras are designed to acquire the tube images from different angles to help avoid image understanding disaster in case of tube overlap of complex tubes. A high precision calibration method based on photography is adopted to provide basic accuracy guarantee of the developed system. Then importantly, a new approach to tube model reconstruction is proposed, including a creative and adaptive tube seed growing method for accurate tube axis reconstruction, and a direct tube end reconstruction method. Furthermore, an automatic method of tube features calculation to help improve the efficiency of tube measurement. Finally, several experiments are performed to verify the reliability, efficiency and high-precision of the developed system. According to the experimental results, the tube measurement process can be finished in about 1.5 s/m. The average deviation of the radial deviation and axial deviation is within 0.062 mm respect to its reference value with the maximum standard deviation of 0.025 mm. For the bending angle and rotate angle, the average deviations from the reference values are within 0.025 degrees and 0.031 degrees with the maximum standard deviation of 0.011 degrees and 0.012 degrees, respectively.