Influence of equipment excitation on flexible carbody vibration of EMU

Abstract

To study the vibration transmission characteristics of a flexible carbody and its suspended equipment, a vertical mathematical model of high-speed electric multiple unit was established with equipment excitation considered. And the dynamic unbalance and impact turbulence excitation from equipment were taken into account in a single-stage and two-stage vibration isolation system, respectively. Results show that the excitation transferred to carbody increases with suspension stiffness but decreases with the equipment mass increasing; the vibration transmission can be reduced by increasing the equipment mass or reduce the suspension stiffness. To avoid vibration resonance, the dynamic unbalance frequency of equipment should be out of the possible range of the carbody flexible modes, and a small stiffness should be applied to reduce the impact turbulence. A small stiffness, however, would result in a large movement of the equipment which is limited by the static deflection requirement, while a great stiffness will transfer high frequency vibration. Therefore, a preferred stiffness should make the suspension frequency of equipment a bit greater than the first bending mode of carbody. Additionally, a 3D rigid-flexible coupled dynamics model was built to verify the mathematical analysis, and they show good agreements. Results show that a two-stage isolation could reduce the excitation transmission and make the vibration of carbody and equipment acceptable.