Measurement method of countersunk rivet flatness based on visual 3D reconstruction

The flatness is a key indicator to evaluate the riveting quality of countersunk rivets on the skin of aircraft or rockets. Aiming at the deficiencies of current measurement methods used by aerospace manufacturers, a measurement method of countersunk rivet flatness based on visual 3D reconstruction is proposed. Through the zonal modulation of the structured light intensity of the projector, the image interference problem caused by the highly reflective skin of aircraft and rockets is solved. A rivet detection algorithm based on an arc feature is designed to realize the accurate identification of rivets in the image. A riveting surface reconstruction algorithm based on region segmentation and parallax constraint is researched, which greatly improves the efficiency of 3D reconstruction. A calculation method based on the local mean is used to improve the stability of the measurement results. The experimental results show that the measurement error of the proposed method is within ±30 μm, the standard deviation of repeated measurement is within 6 μm, and the time of measuring a single rivet is about 2 s. The accuracy, stability, and efficiency of this method meet the requirements.