Dynamics of Independently Rotating Wheel System in the Analysis of Multibody Railroad Vehicles

In this investigation, dynamic characteristics of independently rotating wheel systems are discussed. To this end, a multibody independently rotating wheelset (IRW) model is developed using the method of velocity transformation. The linear stability analysis of a two-axle IRW truck is performed, the hunting stability and vibration characteristics of IRW truck are investigated, and the results are compared with those obtained using the multibody dynamics model. Good agreement is obtained in hunting frequencies and critical speeds. It is shown using the linear IRW equations that since a constant forward speed is assumed for IRW, the longitudinal slip can occur due to the change in the wheel rolling radius. This leads to longitudinal creep forces even in the case of IRW and it contributes to a coupling of the lateral, yaw, and pitch motions of IRW. Furthermore, it is observed in several numerical examples that, due to small self-centering forces of IRW, continuous flange contact occurs on tangent track, while in curve negotiation, flange contacts on outer wheel of the front axle, as well as that on inner wheel of the rear axle, occur. Such an effect can be more significant when sharp curve negotiation is considered as encountered in light rail vehicle applications.