Railway vehicle-mounted dynamic rail cant measurement method based on structured light 3D imaging

Wheel–rail contact-induced wear and rolling contact fatigue are critical contributors to the full life-cycle costs of railway infrastructure. The rail cant, a fundamental parameter influencing wheel–rail geometric contact, plays a pivotal role in determining the contact stress distribution. Deviations in rail cant can lead to misalignment of the contact patch and eccentric loading, exacerbating wear and fatigue. Traditional manual measurement methods rely on point-by-point measurements with rulers, which are inadequate for the extensive and continuous monitoring required under dynamic high-speed conditions. This study proposes a dynamic rail cant measurement method based on structured light 3D imaging to address these limitations. By synchronising line laser projection with camera acquisition, the method enables high-speed reconstruction of the full rail cross-sectional profile. It constructs a geometric model in a world coordinate system. A rail top height difference correction algorithm is introduced to correct posture errors arising from the non-parallel alignment between the measurement beam and the rail. Further, a dynamic correction model for position and posture angles is developed through geometric derivation, and a global system error compensation mechanism is established based on initial line measurement data, achieving closed-loop calibration. Experimental results show that the proposed vehicle-mounted dynamic rail cant measurement system attains field accuracy comparable to traditional manual measurement, yet delivers markedly higher measurement efficiency and substantially lower costs. This research can provide a high-reliability solution for real-time rail cant monitoring and intelligent track maintenance, offering significant engineering value in reducing maintenance costs and extending wheel–rail service life.