Detecting vehicle inter-axle distance, including scenarios with a lifted axle, through the application of a multi-frequency impedance measurement system that utilizes inductive loop sensors
DOI:
https://doi.org/10.24425/mms.2025.154670Abstract
Analysing traffic data collected under varying conditions requires the categorization of vehicle types. One significant issue is that most of the sensors used in vehicle classification systems cannot detect a lifted axle, which often leads to incorrect vehicle categorization. This article recommends utilizing a multi-frequency inductive loop (IL) impedance measurement (MFILIM) system for measuring vehicle inter-axle distances, also in the case of lifted axles. Two slim IL sensors and two wide IL sensors are utilized in the proposed MFILIM system. The vehicle speed and inter-axle distances are evaluated using the vehicle magnetic profile (VMP) waveforms, which are derived from the IL impedance measurements taken simultaneously at three carrier frequencies for a single IL sensor. The potential of the proposed method was validated through a laboratory testbed (LTB) equipped with IL sensor models and vehicle models constructed on a 1:50 scale. Additionally, validation was conducted under real traffic conditions using a road testbed installed adjacent to a commercial weigh-in-motion (WIM) system. The results obtained from several different test vehicles, which passed through the measuring stations multiple times during the experiment, were selected for analysis. The analysis indicated that the MFILIM system outperformed the commercial WIM station by yielding smaller errors in determining inter-axle distances. In addition, it successfully detected a lifted axle in all cases and accurately determined its distance from adjacent axles.References
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