# Train Speed Estimation from Track Structure Vibration Measurements
## 4 Verification of the Train Speed Estimation Method  
### Test Overview  
This paper uses the dynamic tests of China Railway High-speed (CRH) track as an example to verify the validity of the proposed train speed estimation algorithms. The dynamic test site was located on the bridge China Railway Track System II (CRTS II) slab ballastless track with a curve radius of 7000 m and an outer line height of 115 mm. The CRTS II slab ballastless track consists of rail with a grade of 60 kg/m, elastic fastener, prefabricated track plate, mortar adjustment layer and supporting layer. The track slab is 2550 mm wide, 200 mm thick and 6450 mm long.  
The rail acceleration was detected using a DH131E (with measuring range of 5000 m\(\cdot\)s\({}^{-2}\) and sensitivity of 1 mV\(\cdot\)s\({}^{-2}\)) impedance converter accelerometer. The slab acceleration was detected using a DH187E (with measuring range of 1000 m\(\cdot\)s\({}^{-2}\) and sensitivity of 5 mV\(\cdot\)s\({}^{-2}\)) impedance converter  
Figure 8: Frequency domain diagram of vertical displacement dynamic response signals.  
Figure 9: Low-pass filtered displacement signals (the red circle indicates the passing moments of the train bogies).  
accelerometer. The vertical vibration of the slab displacement was detected using a DH821-10 (with measuring range of 10 mm and resolution of 0.005 mm) linear displacement sensor. The slab acceleration was detected using a DH187E impedance converter accelerometer. The sensors were pasted on the cleaned rail and track slab, as shown in Figure 10. All the test signals were collected using a DH5902 dynamic data acquisition device at a sampling frequency of 10k Hz. The sensors and the device were produced by Donghua Testing Technology Co., Ltd., Taizhou, Jiangsu, China. The sensor arrangement is shown in Figure 10 and Table 2, respectively. There is a gap between the slab and the support layer at one wide and narrow joint while the other side is healthy.  
The trains in the test are all CRH series high-speed trains. As shown in Figure 7, the center distance of the bogies in the same carriages \(l_{\text{a}}\) is 17.5 m and the center distance of the bogies in adjacent carriages \(l_{\text{b}}\) is 7.5 m. The threshold condition coefficient \(\lambda\) of slab displacement, slab acceleration, and rail acceleration is taken as 0.6, 0.4, and 0.3, respectively. The significance level of the Grubbs criterion is equal to 0.05.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sensor** & **Location** & **Content** & **The Track Curve** & **Structure State** \\ \hline D1 & Slab & Displacement & Inside & Healthy \\ D2 & Slab & Displacement & Inside & Layer gap \\ D3 & Slab & Displacement & Outside & Healthy \\ D4 & Slab & Displacement & Outside & Layer gap \\ A1 & Rail & Acceleration & Inside & Healthy \\ A2 & Rail & Acceleration & Inside & Layer gap \\ A3 & Rail & Acceleration & Outside & Healthy \\ A4 & Rail & Acceleration & Outside & Layer gap \\ A5 & Slab & Acceleration & Inside & Healthy \\ A6 & Slab & Acceleration & Inside & Layer gap \\ A7 & Slab & Acceleration & Outside & Healthy \\ A8 & Slab & Acceleration & Outside & Layer gap \\ \hline \hline \end{tabular}
\end{table}
Table 2: The sensor arrangement.  
Figure 10: Sensor location diagram.