Objective The straddle monorail transit operational practice has revealed that the vehicle vertical stability often exceeds standard limits. To enhance this stability, it is necessary to conduct research on the optimization of suspension system parameter matching.

Method Based on the establishment of vehicle dynamics model and running tire non-linear UA model according to GB/T 5599—2019 Specification for dynamic performance assessment and testing verification of rolling stock, in-car acceleration valuation points are set to analyze the current vehicle operational stability. Under the 70 km/h operating speed condition on a 500 m straight track beam, stability indices at evaluation points A and B are calculated. Using orthogonal test variance analysis, a sensitivity analysis is performed on the parameters of 10 suspension systems, including the running wheel system, air springs, and shock absorbers. Six primary influencing factors are identified: running wheel vertical damping, running wheel stiffness, shock absorber damping, air spring vertical stiffness, air spring vertical damping, and air spring radial stiffness. Taking the RMS (root mean square) values of vertical acceleration at points A and B as optimization objectives, a parameter matching optimization study is conducted with NSGA-Ⅱ (non-dominated sorting genetic algorithm Ⅱ) on a co-simulation platform of modeFRONTIER and ADAMS.

Result & Conclusion  Before optimization, the vertical stability indices W at points A and B are 2.577 4 and 2.674 1 respectively, both exceeding the standard limits. After parameter optimization, the 488th set of schemes is selected as the optimal combination, leading to a 5.99% and 7.07% improvement in the vertical stability indices at points A and B, respectively. In the end, all W values fall below 2.5, meeting the requirements of the specified limit values.