Edge-based 3D vibration measurement of rotating cylinder-shaped structure through epipolar line-based corresponding point extraction between two camera images

Abstract

Three-dimensional (3D) vibration measurements are important for monitoring rotating structures in order to reproduce the directional displacements of vibration signals such that they are similar to the actual movement. Photogrammetric techniques, which can be used to determine the relationship between 3D objects and their two-dimensional images, allow 3D vibrations in a structure to be measured without direct contact. Therefore, we herein present a multipoint 3D vibration measurement approach for rotating cylinder-shaped structures, which performs the imaging of a structure from two directions using two cameras. First, an epipolar line-based corresponding point extraction technique is applied to extract the corresponding regions of interest (ROIs) in videos acquired by the two cameras placed at 90° to the structure. Subsequently, an edge-based vibration measurement approach is used to detect vibrations in the corresponding ROIs. Noise reduction is then applied to reduce the noise, induced by the cameras or edge-based vibration measurement technique, by extracting and employing the frequencies at which the vibrations were occurring to the phase-based motion magnification technique. Subsequently, vibrations in the corresponding ROIs of the magnified videos are detected. For 3D plotting, the two vibration signals are combined. Simulation and real datasets are prepared for the qualitative and quantitative assessments of the proposed method. The simulation data results are compared with the results obtained before noise reduction, those obtained after noise reduction via bandpass filtering, and the reference data. A 3D vibration analysis is performed on the real data in multiple ROIs. The results yielded by the proposed method can be used to identify the weak points in a rotating cylinder-shaped structure that cause the structure to function abnormally.