Simulation and experimental investigation on stability improvement for high-speed railway vehicles

To address the degradation of critical speed caused by wheel/rail wear in high-speed trains with passive suspensions, this study investigates stability improvement through active control using integrated numerical and experimental approaches. A three-degree-of-freedom vehicle dynamics model is established, incorporating a nonlinear wheel/rail relationship fitted by measured data in a field test. Stability and complex dynamic behavior analysis of the vehicle system under both passive suspension and active control are thoroughly analyzed via simulations. The simulation results illustrate that under a passive suspension state, the vehicle at the end-worn wheel stage undergoes Hopf bifurcation followed by period-doubling bifurcation, eventually leading to chaotic motion. In contrast, linear control effectively delays the Hopf bifurcation point, increases the critical speed, and suppresses nonlinear dynamic behavior at higher operating speeds. Concurrently, a full-scale roller rig test bench was employed to conduct dynamic experiments on a high-speed vehicle equipped with a switch-type semi-active yaw damper for active control implementation. The experimental results show that when active control is considered at the end-worn wheel stage, the semi-active yaw damper is effective in improving hunting stability of the vehicle system, whereas its effect is limited during the new wheel stage.