Effects of periodic structures on friction-induced vibrations in catenary-pantograph systems

Friction-induced vibration in catenary-pantograph systems is a well-known instability phenomenon that has not been sufficiently investigated. This instability accelerates the wear of contact wires and requires a train driver to confirm safety, which leads to train delays. Therefore, it is important to elucidate the instability mechanisms and establish countermeasures. To address this issue, we conducted experiments using a real pantograph and a test facility that can simulate sliding conditions by rotating a rigid disk. These experiments characterized the instability reported in actual rail operations. Furthermore, numerical investigations found that the experimental results could be explained by assuming Coulomb friction for an experimentally validated pantograph model. However, this previous study did not examine the effects of the periodic catenary structures or propose countermeasures for their instability contribution. In this study, experiments and simulations based on actual equipment were conducted to investigate the effects of periodic structures. The simulations integrated a finite element method-based catenary model with a flexible multibody dynamics-based pantograph model. The experimental and numerical investigations clarified that the instability is caused by the asymmetry of the stiffness matrix due to Coulomb friction, and that standing waves formed in the contact wires between hangers significantly affect stability. Furthermore, the results suggested that these waves could be the basis of countermeasures for preventing instability. These results can contribute to the design of catenaries and pantographs with improved stability.