Influence of traction motor suspension on running stability of a high-speed rail vehicle and its active control

For high-speed bogie, the traction motor contributes to a large mas to the bogie system then influences the running stability. This study proposed to actively control the suspension parameters of the traction motor to enhance the running performance of the high-speed bogie. A simplified vehicle dynamics model was firstly built with nonlinear wheel/rail contact integrated, then a root locus analysis was performed to examine the relationship between the motor suspension frequency and critical speed of the vehicle system. Based on this, the necessity of active control on the motor suspension was elaborated, and it was pointed out that the active suspension control can adjust the suspension frequency of traction motor to increase the critical speed of the vehicle system under different wheel/rail conicity states. Furtherly, bifurcation analysis is carried out to show that the active control may affect the vehicle bifurcation characteristics. According to the calculations, with fixed lateral damping ratio of the motor, the linear critical speed of the system has increased by 4.8% -24.6%, with fixed lateral damping of the motor, the linear critical speed of the system has increased by 1.9% -30.9%, and possible impact of time delay and countermeasures were explained. Furtherly, optimization can be performed using the nonlinear control laws with the cubic terms concerned.