Collision-Resistant High-Precision Geometric Metrology for Inner Wall Topography in Cylindrical Confined Spaces

Precision topographic measurements of the inner wall are essential for quality control of fluid intake in cylindrical cavities. Mainstream geometric measurement strategies often fail to function effectively in cylindrical confined spaces. To this end, this paper proposes a collision-resistant and high-precision geometric measurement strategy that integrates circular structured light and line structured light, enabling both inner diameters and 3D shape measurements. First, dual symmetrically arranged line-structured stripes are projected onto the end face of cylindrical parts for position initialization and motion tracking. This procedure prevents collision risks induced by excessive inclination angles or insufficient working distances. Second, the circular-structured stripe is projected onto the inner wall of cylindrical cavities, thereby obtaining high-precision 3D surface profiles. Finally, the 3D reconstruction of the inner wall topography is completed by carrying the probe on an arbitrary moving platform. Compared to existing methods, the proposed method offers the advantages of collision-resistant, high-precision measurements, and system integration. Experimental results demonstrate that the developed probe provides reliable, high-precision, and high-efficiency measurements when mounted on a CNC machine for various cylindrical cavities.