Three-Dimensional Vibration Measurement Method for Overhead Contact Lines Using a Stereo Camera

We have developed a non-contact stereo-vision method to measure the three-dimensional vibration of overhead contact line equipment during train passages. Because no special markers need to be affixed to the measurement target, the technique enables fully non-contact measurement from a distance, including during setup. This paper presents an overview of the developed measurement methodology and the results of validation tests. In this method, intrinsic camera parameters are calibrated in a laboratory using a calibration pattern imaged at multiple angles, and extrinsic parameters are determined on site for flexible deployment. Digital image correlation tracks target points captured by the stereo camera, and triangulation reconstructs their three-dimensional trajectories. In a verification test assessing the applicable frequency range, we confirmed that millimeter-scale vertical vibrations of a dropper fitting located approximately 5 m from the camera could be measured up to sub-20 Hz. Furthermore, in tests on actual overhead contact line equipment, the three-dimensional displacement of a dropper fitting located 25-30 m from the camera was measured during pantograph passage and compared with the vertical and lateral displacements recorded by a displacement gauge. The results showed good agreement between the time history waveforms of both measurements, confirming the method’s effectiveness.