Novel Dynamic Chord Reference Method in Railway Track Irregularity Measurement Based on Vehicle

The chord reference method (CRM) is a well-established approach employed in railway maintenance for identifying and quantifying track irregularity. However, the static CRM is characterized by a substantial amount of labor involvement and a correspondingly low level of efficiency. The process of employing dynamic inertial reference method often presents challenges, particularly when it comes to identifying the appropriate reference base in an intuitive manner. If dynamic irregularity can be transformed into dynamic CRM value, the advantages of static CRM in maintenance can be effectively exerted, and the shortcomings of low efficiency and heavy workload can be overcome. This paper presents an innovative methodology for dynamic CRM utilizing vehicle as platform. The proposed method aims to improve the accuracy and efficiency of CRM assessments, particularly those requiring real-time or continuous inspection. Firstly, the pitch angular velocity of the vehicle is measured by incorporating gyroscope-based pitch angular velocity sensors into vehicle. Secondly, the dynamic CRM value is computed by employing the basic chord length of 0.5 m, derived from the pitch angular velocity of the vehicle. Subsequently, we developed a unique filter that generates dynamic CRM values in response to diverse chord lengths, including 10 m, 20 m, and so on. Finally, an experimental comparison is conducted to discern the variations between the dynamic CRM value and spatial curve amplitude value of track irregularity on a specific railway line. A statistical approach is employed to derive a correction coefficient, which aids in mitigating discrepancies and enhancing the accuracy of measurements. The results from real-world tests are provided, which demonstrate that the proposed methodology outperforms static CRM and dynamic inertial reference method by noticeable.