Improvement of Carbody Hunting Stability in High-Speed Trains via Primary Suspension Longitudinal Active Control

This study investigates the mitigation of carbody hunting instability in high-speed trains (HSTs) and proposes an active control strategy based on primary longitudinal dynamics. Field tests were first conducted to characterize the vibration responses of the carbody and bogies under hunting instability conditions. Based on the identified harmonic characteristics, a carbody–bogie amplitude–frequency hunting detection (CBAF-HD) method was developed and validated using the measured data. To suppress hunting instability, an active control strategy is proposed in which the bogie hunting frequency is regulated through adaptive modification of the primary longitudinal stiffness. A simplified control-oriented bogie model is employed to preliminarily demonstrate the effectiveness of a proportional–integral–derivative (PID) controller. Furthermore, a 17-degreeof-freedom (DOF) vehicle dynamic model is established to investigate the influence of primary longitudinal stiffness on bogie hunting behavior and overall system stability. A full-scale nonlinear dynamic and control co-simulation model is subsequently developed for comprehensive evaluation. The PID controller parameters are optimized using particle swarm optimization (PSO), resulting in enhanced control performance. The results indicate that the proposed strategy effectively modifies the equivalent primary longitudinal stiffness and introduces additional damping, thereby suppressing bogie hunting and preventing its coupling with the carbody suspension modes. Numerical simulations demonstrate that the proposed active control reduces the root-mean-square (RMS) lateral vibration of the carbody by approximately 80% and that of the bogie by more than 60%, confirming the feasibility and effectiveness of the proposed method.