Metro vehicle lateral vibration characteristics based on vehicle-equipment coupling under service conditions

To reduce lateral vibrations of vehicle body and improve the comfort of metro vehicles during long-term service, a lateral dynamics model of metro vehicles with underframe equipment was built. The dynamic change rules in the distribution of vehicle speed and the equivalent conicity reflecting the wheel-rail contact state under service conditions were investigated. The lateral vibration characteristics of vehicle-equipment coupling were obtained, and a parameter design method for reducing lateral vibrations in vehicle-equipment coupling was formulated. Analysis results indicate that the service conditions of metro vehicles change dynamically with the variations in vehicle speed and equivalent conicity. The critical speed of the vehicles decreases and the lateral vibrations intensifies with an increase in the equivalent conicity of wheel-rail contact. The characteristic frequency of lateral vibration increases linearly with the increase in vehicle speed and equivalent conicity, and its value is concentrated in the low-frequency range of 1-3 Hz. When vehicle body and equipment undergo lateral vibration coupling, an optimal matching relationship exists between equipment mass and elastic suspension stiffness. Selecting an appropriate suspension stiffness can significantly reduce the lateral vibrations of vehicle body. Furthermore, increasing the width and roll inertia of underframe equipment helps reduce the lateral vibrations of vehicle body. To suppress the lateral vibration of vehicle-equipment, attention should be paid to the selection of lateral suspension stiffness, which is recommended to be 6.0×10⁴ N·m^-1. The lateral vibration frequency of equipment is made close to that of vehicle body through the adoption of a proper elastic suspension connection between underframe equipment and vehicle body. The lateral vibration of vehicle body can be reduced by utilizing the same frequency coupling vibration between vehicle and equipment, thereby improving the quality of vehicle operation.