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Evaluating Railway Vehicle Running Stability Based on Detection of the Three-Dimensional Center of Gravity



Author(s)

Kiwami Watanabe, Xian Chen and Yutaka Watanabe

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DOI:10.17265/2328-2142/2026.04.001

Department of Logistics and Information Engineering, Tokyo University of Marine Science and Technology, Tokyo 135-8533, Japan

Railway vehicle stability is an important factor affecting operational safety and ride quality. This study applies D3DCG (Detection of Three-Dimensional Center of Gravity) to evaluate the running stability of passenger railway vehicles without requiring prior knowledge of vehicle mass or spring stiffness. Field measurements were conducted on two commuter railway lines in the Greater Tokyo area, Japan using a motion sensor installed inside operating vehicles. After vertical acceleration and roll angular velocity measurements were taken during service operation, data were analyzed using FFT (Fast Fourier Transform) to extract dominant vibration frequencies. The obtained natural frequencies were substituted into the D3DCG equations to estimate the vehicle center of gravity height and the corresponding critical center of gravity position (L_max), which were used as rollover stability indicators. The estimated center-of-gravity positions were generally distributed within a physically reasonable range relative to the vehicle structure. Furthermore, an interesting tendency was observed in the calculated L_max values: the values initially decreased and subsequently increased along the measured sections. This tendency suggests that the stability margin of railway vehicles might vary depending on running conditions and vibration characteristics. The findings indicate that D3DCG-based analysis can provide a practical approach for evaluating railway vehicle stability using operational vibration data without requiring direct structural measurements.

D3DCG, center-of-gravity estimation, railway vehicle, running stability.

Kiwami Watanabe, Xian Chen and Yutaka Watanabe. (2026). Evaluating Railway Vehicle Running Stability Based on Detection of the Three-Dimensional Center of Gravity, Journal of Traffic and Transportation Engineering 14 (2026) 153-161