Abstract: In order to avoid or restrain the primary hunting stability of rail vehicles, correlation between the primary hunting stability and suspension damping parameters under the damping ratio of 0 and 5% is calculated based on the analysis of suspension parameters on the vehicle modal frequency. The method to improve the stability of vehicle hunting motion by optimizing suspension parameters is obtained. The results show that when selecting different damping ratios to calculate the critical stability, the range of damping parameters varies greatly. The lateral damping parameter in a certain range or a larger vertical damping is beneficial to keep the carbody upper sway motion stable. Too large or small vertical damping and too small lateral damping are detrimental to the lower sway stability of the car body. The increase of lateral or longitudinal damping parameter is beneficial to the yaw motion stability of the car body.

Key words: railway vehicle, hunting motion, model analysis, stability analysis