Influence of system parameters on the stability limit of the undisturbed motion of a motor bogie

Abstract

In this article, the stability limit of the undisturbed motion of a simple railway motor bogie whose traction motors are fully suspended on the bogie frame is analysed. Under appropriate assumptions, equations of motion for the vehicle system are deduced by considering the lateral and yaw motions of the bogie frame, wheelsets and traction motors. Using root locus analysis, eigenvalues and eigenvectors of the equations are calculated, and a stability assessment for determining the bifurcation point is proposed. The vehicle speed at the bifurcation point is defined as the bifurcation speed where the equilibrium position of the vehicle system loses stability. Parametric studies are undertaken in order to investigate the respective effects of the traction motor's parameters on the stability of the vehicle system. It is found that the stiffness, damping and mass properties of the traction motor have significant influences on the bifurcation speed. There exists an optimum natural frequency for the motor suspension, below which a relatively high bifurcation speed is obtained. Finally, the effect of the bogie's parameters on the optimum natural frequency is investigated, and it is shown that the optimum natural frequency is significantly affected by the primary and secondary suspensions, and the wheel/rail contact conditions.