Dynamic Inspection of Rail Wear via a Three-Step Method: Auxiliary Plane Establishment, Self-Calibration, and Projecting

Structured-light vision (SLV) is a standard approach for inspecting rail wear. However, it is incompetent for dynamic inspection due to the random vibrations in the line laser projector. In this paper, a three-step distortion rectifying method is introduced to address this issue. Given an image with two rail profile stripes, the first step involves parallelity constraint-based establishment of an auxiliary plane whose normal vector is parallel with the rail longitudinal axis. The establishment is only dependent on the intrinsic camera parameters, which improves the robustness of the auxiliary plane to the random vibrations in the line laser projector. In step two, this auxiliary plane is utilized for the autonomous calibration of the line structured lights. The proposed self-calibration is achieved by minimizing the point set mapping errors on triple matching primitives such as rail jaw, railhead inner, and rail foot and requires only two laser stripes. After these two steps, two rail profiles are reconstructed from the double-line SLV without known poses, and the distorted one is projected onto the auxiliary plane for distortion rectifying. It is able to deliver more precise rectifying than the parallel-line SLV and cross-line SLV, even if the inspecting task is performed dynamically. With the comprehensive experiments, we test our scheme and compare it with the related methods. The experimental results verify that the proposed method outperforms the previous works in terms of the accuracy and robustness for the dynamic wear inspection.