# Prediction of Key Parameters of Wheelset Based on LSTM Neural Network
## 3 Wheelset Key Parameter Analysis
### Analysis of Key Parameter Evolution  
The phenomenon of uneven wear may occur during the operation of the wheelset, and this study focuses on both left and right wheels. Under normal wear conditions, as the vehicle runs, the values of flange thickness \(Sw\) and wheel diameter \(D\) decrease, while the value of flange height \(Sh\) increases. When these key parameter values reach their limits, reprofiling is carried out to increase the flange thickness \(Sw\) value and decrease the flange height value \(Sh\) by reducing the wheel diameter D This ensures that the wheelset meets the safety requirements. Approximately 8-10 mm of wheel diameter loss is required to restore 1 mm of flange thickness [21]. The changes in wheel diameter, flange thickness, and flange height values of the wheelset on a certain line between 2017 and 2022 are shown below.  
As Figure 7 shows, the wheel diameter value decreases continuously as railway vehicles run. The decreasing trends in both left and right wheels are basically the same, and there is no excessive deviation of the wheel diameter between the two sides. However, in June 2019 and October 2020, the decreasing slopes became steeper due to reprofiling for the excessive difference in flange thickness of left and right wheels.  
From Figure 8, it can be seen that the flange thickness value decreases continuously as railway vehicles run. The trends in both left and right wheels are basically the same, but the value of the right wheel is significantly higher than that of the left wheel. In June 2019, the difference in flange thickness values between the left and right wheels reached its limit, then reprofiling was carried out. In October 2020, due to the difference in flange thickness values between the left and right wheels approaching the limit again, the wheels underwent a second reprofiling. After the first reprofiling, the flange height values were 29.3 mm for the left wheel and 30.2 mm for the right wheel. Before the second reprofiling, the flange height values were 28 mm for the left wheel and 29.3 mm for the right wheel. The change was 1.3 mm for the left wheel and 0.9 mm for the right wheel, and the wear difference between the left and right wheels was 0.4 mm. Combined with the analysis of the cause of wheelset uneven wear, it is considered that the wheelset has experienced uneven wear.  
From Figure 9, it is shown that the trends in flange height values for the left and right wheels are basically the same as railway vehicles run. The flange height values continuously increase before June 2019 and experience a sudden drop around June 2019 due to the excessive difference in flange thickness between the left and right wheels. Reprofiling was performed on the wheelset, and the reprofiling template required a flange height value of 28 \(\pm\) 0.5 mm after reprofiling. In October 2020, a second reprofiling was  
Figure 6: Schematic diagram of flange parameters.  
conducted, and there was not much change in the flange height values. However, they gradually increased during operation after repro  
Figure 8: Changes in the flange thickness of a certain wheelset.  
Figure 7: Changes in the wheel diameter of a certain wheelset.