Establishment and validation of a locomotive–track coupled spatial dynamics model considering dynamic effect of gear transmissions

Gear transmission is a key element in a locomotive for delivery of traction power from the electric motor to the wheelset. Its dynamic performance has a direct effect on the operational reliability or even safety of the locomotive or the train. In this paper, based on the classical vehicle–track coupled dynamics theory and the gear dynamics theory, a locomotive-track coupled spatial dynamics model is established where the dynamic effects from the gear transmissions are considered. In this model, the gear transmission system and the classical locomotive–track system are coupled with each other via wheel–rail contact interface and the gear mesh interface. The dynamic interactions between the rotational motions of the power transmission system, the vertical, lateral, longitudinal, roll, yaw and pitch motions of the components in a locomotive are fully included. This more comprehensive dynamics model of the locomotive–track system enables detailed investigations on the system dynamic performance under the complicated excitations from both the track geometrical irregularity and the internal mesh process of gear pairs (e.g. time-varying mesh stiffness, gear errors), especially the dynamic responses of the gear transmission in the complete vehicle vibration environment. This model is finally validated by comparisons with the field test data in the time- and time-frequency domains. And it is capable of being used for dynamics related assessment, such as vibration, fatigue and damage of the powered railway vehicles considering gear transmissions, especially for traction and/or braking conditions.