Analysis of the dynamic characteristics of the gear-shifting process under external excitation

This study focuses on a novel clutchless and synchronizer-free drive system designed explicitly for pure electric vehicles. In contrast to the majority of previous research that solely considers internal excitations, this study not only incorporates various non-linear factors such as time-varying friction forces, time-varying mesh stiffness, and damping associated with internal excitations but also places significant emphasis on analyzing the impact of non-linear external excitations, including road surface unevenness and motor torque fluctuations, on the shifting process of the drive system. Subsequently, a non-linear dynamic model of the shifting process is established. In the modeling process, departing from the traditional two-degree-of-freedom quarter vehicle dynamics model, this study adopts an elastic tire-body and elastic tire-tread tire model, enabling the establishment of a highly accurate multi-degree-of-freedom quarter vehicle dynamics model. The simulation results indicate that road surface roughness and motor torque fluctuation significantly impact the gear-shifting process and the impact of road surface roughness increases with the level of roughness. Moreover, the effect of motor torque fluctuation on the gear-shifting process varies depending on different factors and is not simply additive. Consequently, when formulating and optimizing shifting strategies, it becomes imperative to consider various external factors. The research methodology integrates these factors into the dynamic analysis of the shifting process, providing a theoretical basis for developing effective shifting control strategies while considering external excitations.