# Influence of Metro Track Irregularities on Pantograph Vibration and Its Interaction with Catenary
## 5 Optimization Suggestions  
Based on the above calculation and analysis, there are many broadband spectral peaks in the track irregularity of Metro Line 1 in Z City. However, the short-wave irregularity cannot lead to the abnormal vibration and the contact force of PC, so it can be considered that these abnormal vibrations and forces are related to the medium- and long-wavelength irregularity. After a comprehensive analysis, it can be considered that the track irregularity with wavelengths of 2-4 m and 9-16 m plays an important role. Especially for Z City Metro Line 1, the amplitude of the irregularities in the two wavelengths is too large compared with other typical metro line irregularity spectra, which aggravates the vehicle vibration and strengthens the PC interaction. Therefore, the target object in the manuscript is whether the PC interaction can be reduced by decreasing the amplitude of the track irregularities in the two wavelength regions. The irregularity with the wavelength of 2\(\sim\)4 m was mainly caused by the rail straightening operation. The amplitude of the irregularity can be reduced by grinding the rail, replacing the rail, or improving the rail straightening operation technology. The irregularity with the wavelength of 9-16 m may be caused by the rail straightening operation, the welded joint, or the periodic structure irregularity of the base. Irregularities within the wavelength should be determined according to field investigation, and maintenance measures such as rail grinding, replacement with longer rails, and the repair of the periodic settlement of the base and the foundation can be taken. To verify the effectiveness of the above suggestions, the manuscript simulates the on-site maintenance, and the irregularities of the two wavelengths of 2-4 m and 9-16 m are filtered by 30% and 60%, respectively (as shown in Figure 13), and then the dynamic calculation is carried out to verify the reasonableness of the suggestions. Among them, maintenance 1 means that the amplitude of 2-4 m and 9-16 m wavelength irregularities is reduced by 30%, and maintenance 2 means that the amplitude of these two wavelength irregularities is reduced by 60%. The purpose of setting these two calculation conditions is to fully illustrate the effect of reducing the amplitude of the two-wavelength part on controlling the pantograph-catenary interaction. Figure 13: The two maintenance suggestions. The track irregularity after filtering is substituted into the dynamic model for calculation, and the results are statistically analyzed and compared with the original responses. The vertical and lateral accelerations of the pantograph strip are shown in Figure 14 and the statistical values of the acceleration are shown in Table 3.  
According to Figure 14, the vibration responses of the pantograph strip are significantly reduced after adopting the suggestions proposed in the manuscript, especially in the lateral vibration, where the overall frequency distribution is closer to the axis x = 0. It can be calculated from Table 3 that the maximum lateral acceleration of the pantograph strip decreases by approximately 62% and the effective value drops by approximately 50% under the condition of maintenance 1, while the maximum value decreases by approximately 63%, and the effective value drops by approximately 74% under the condition of maintenance 2. The significant reduction in the lateral vibration indicates that it is necessary to control the 9-16 m and 2-4 m wavelength track irregularities in Z City Metro Line 1. The comparison of the PC contact force is shown in Figure 15, and the statistical characteristic values are shown in Table 4.