Video-Based Micro-Vibration Measurement for Hydraulic Structures in Field Environments Using Phase-Based Motion Extraction

Abstract

Hydraulic structures subjected to prolonged operational conditions inevitably experience damage and potential structural resonance, which threaten their stability and safety. Structural health monitoring (SHM) is a well-established approach to ensuring safety; however, conventional methods primarily rely on contact sensors, which are inadequate for comprehensive monitoring of large and complex structures. Video-based noncontact monitoring techniques effectively address this limitation. This study proposes a field-deployable, phase-based video method to measure micro-vibrations of large hydraulic structures. Rather than batch processing full frames, vibration time histories are extracted from user-defined pixels or pixel groups, enabling efficient region of interest (ROI)—level analysis with synchronized high-speed videos. We then assess the method's robustness under varied illumination conditions, shooting angles, and scales, and visualize micro-motions using frequency-selective motion magnification. On an aging aqueduct, video-derived responses show strong agreement with those obtained via displacement sensors; the correlation coefficient with sensor data reaches up to 0.96, accurately capturing the spectral peak bands within the 0-100 Hz and demonstrating exceptional robustness in the 0-20 Hz. Based on the discussion of practical limits, we provide guidelines for low-texture, large-scene monitoring. Adequate and uniform illumination is essential, and local fine-scale features can significantly improve accuracy. The correlation coefficient can be increased by 0.1-0.3. Perpendicularity between the shooting angle and the target vibration direction is critical for obtaining high-precision data.

Keywords

field environments / hydraulic structure / motion magnification / noncontact measurement / phase-based optical flow

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2025 Tianjin University and John Wiley & Sons Australia, Ltd.