A Study on Dynamic Measurement System of Contact Wire Wear in Electrified Railway

Measurement Method for Contact Wire Wear Based on Stereovision

“…For the vision measurement method, the wear surface of contact wire is illuminated, and the wear width is extracted by analyzing the image taken by the cameras. Several vision measurement methods were reported, such as structured light vision measurement [8][9][10] and stereovision measurement [11][12][13]. For example, researchers from RTRI developed a contact wire wear measurement system based on structured light vision measurement [8].…”

“…Great efforts have been made to overcome the above challenges. Laser diodes combined with interference filters are used as the active light source, which improves the image SNR (signal-noise ratio) in daytime inspection [7,12]. Due to considerations of operational safety and laser temperature control, the power of the laser needs to be carefully designed.…”

“…To minimize the influence of the variation in contact wire height on measurement, Van Gigch et al [15] and Borromeo et al [7] proposed a method of adjusting the focal lengths of cameras online separately, while Kusumi et al [16] developed a method for keeping a constant distance from cameras to contact wire by controlling the mirrors. You et al [12] derived the equation of calculating the wear width using the pinhole camera model, which involved the impact of height variation on resolution. On the other hand, stereo matching is another challenge in stereovision measurement.…”

“…Currently, little attention is being paid to the impact of stagger variation on resolution. In most existing studies, the focus is on minimizing the influence of the variation in contact wire height on measurement [7,15,16] or on evaluating the impact of height variation on resolution [12]. In this study, the impact of both the height variation and the stagger variation on the image resolution has been taken into account by using the lookup-table method, which ensures the accuracy of the wear measurement of contact wires.…”

“…In order to highlight the grayscale feature of the wear surface and improve the image SNR in daytime inspection, a new kind of high-speed synchronized stroboscopic lighting technology using monochromatic LED lamps combined with narrow band-pass optical filters is developed as an alternative active lighting method. Compared with the laser diode lighting method reported in the literature [7,12], the stroboscopic LED lighting method avoids the risk of laser operation and is harmless to nearby people. In addition, there is no need to design a precise mechanical adjustment device to make the scanning plane of the line-scan camera coincide with the laser irradiation plane.…”