Uncertainty Analysis and Evaluation of Gauge Measurement in Track Geometry Inspection Systems

To ensure the credibility of measurement data from the Track Geometry Detection System (TGDS) and to achieve its dynamic and accurate evaluation, this paper analyzes and assesses the sources of uncertainty in the measurement of track geometric irregularities by the track inspection system based on a calibration test bench in the laboratory. To address the issue that the track inspection system is prone to sporadic outliers under electromagnetic interference and vibration, while conventional statistical methods are sensitive to outliers and tend to overestimate the repeatability uncertainty, this paper introduces a robust statistical method based on median absolute deviation (MAD) to evaluate the uncertainty introduced by repeatability. This robust approach effectively suppresses the influence of outliers by using the median instead of the mean and absolute deviations instead of squared deviations, thereby yielding a more realistic and reliable estimate of repeatability. Taking track gauge measurement as an example for uncertainty evaluation, experimental results show that the expanded uncertainty U = 0.64 mm, which satisfies one-third of the tolerance requirement for track gauge measurement, verifying the feasibility of the proposed method. The quantitative results of uncertainty sources in this paper can be used as Type B input for uncertainty evaluation in field practical measurements, providing a reliable metrological basis for the uncertainty evaluation of track inspection systems. Meanwhile, the dynamic evaluation of track inspection systems is realized, filling the gap in their dynamic and reliable evaluation under complex interferences.