High-speed Rotating Blade Condition Monitoring Technique Using Phase-locked Signal and Phase-based Displacement Measurement Method

Displacement measurement techniques using camera systems reduce the need for contact sensors and enable high-resolution, non-contact displacement measurements, which are widely used for structural health monitoring. However, measuring rotating structures can cause issues such as motion blur. This study presents a camera-based condition-monitoring technique applicable to operational conditions. First, a phase-locked signal is used to generate stationary images showings the sub-pixel-level micro-displacements of rotating objects. Subsequently, the phase-based optical flow (POF) method measures the displacement of the structure and is used for condition monitoring. The POF technique allows defect visualization by analyzing full-field displacement measurements, thereby enabling the evaluation of the structural condition. Experimental results demonstrate that the proposed method accurately detects and locates bolt-loosening defects in rotating structures, contributing to effective monitoring of rotors in applications such as urban air mobility (UAM).