Suspension parameters for low-damped carbody oscillation of high-speed railway vehicle

This study presents an optimization method to design the suspension properties associated with low-damped carbody oscillations for high-speed railway vehicles. In this method, the least damping ratio for the low-frequency modes in the entire service speed range and the critical speed for a worn wheel are proposed for the design objectives. Based on the linearized vehicle model, a genetic algorithm is applied to determine the optimal suspension properties to maximize the least damping ratio while maintaining the critical speed above the desired speed. The optimization results show that the proposed method can enhance lateral ride comfort by eliminating the region where the least damping ratio of the carbody mode decreases excessively and securing a constant for the entire service speed range. The least damping ratio was improved from approximately 5.7% to 15.6% and the critical for the worn wheel increased from approximately 430 to 499 km/h. Parametric studies are conducted to investigate the influence of the tolerances of the suspension properties, and the results provide useful information regarding the manufacture of suspension elements and assembly of the bogie system. The validity of the optimized suspension properties is verified from the simulation results using railway vehicle dynamics software.