Modal parameters-based hunting stability analysis of high-speed railway vehicles considering full range of equivalent conicity

The balance of vehicle parameters to avoid both the carbody and bogie hunting instabilities existing at different stage of vehicle operation is a long-standing problem. However, most of the existing researches focus on a single form of hunting instability and only take specific value of equivalent conicity as the worst case of wheel-rail contact relationship. To face this challenging problem, this paper studies the hunting stability of high-speed railway vehicles from the perspective of modal parameters based linearized analysis. The root locus analysis is carried out first to observe the modal information and hunting stability. The continuous modal tracking method is exploited to understand the variation regularity of each mode under the speed parametric excitation, especially when the frequency coupling occurs. Two objective functions related to the minimal damping ratio are proposed to indicate the severity of carbody and bogie hunting instabilities, respectively. The proposed objective functions consider the full range of running speed and wheel-rail contact conicity during operation. Starting from the objective functions, the sensitive analysis and a vector evaluated genetic algorithm are implemented to optimize the suspension parameters. Finally, the optimal solution of the suspension parameters is obtained after a generation of 20. The research method presented in this paper deepens the understanding of hunting motion and improves the vehicle stability in a simple, efficient and effective way.