Experimental Investigation and Control of Driveline Torsional Vibrations during Clutch-to-Clutch Shifts of Electrified Vehicles

An electrified vehicle equipped with a stepped-ratio transmission and clutch(es) requires precise control of the clutch actuator(s) and power sources to achieve optimal gear shift performance, which is characterized by smooth and swift gear shifts. Owing to the absence of the smoothing effect of torque converters, dual-clutch transmission (DCT) powertrains are prone to inducing abrupt shift shocks—particularly during rapid clutch-to-clutch shifts. Balancing the smoothness and speed of shifts is a significant challenge and was the key focus of this study. Multiple experiments and model-based analyses were conducted to investigate the tradeoff between smoothness and shift time during the clutch-to-clutch shifts of a parallel-type hybrid electric vehicle with a dry DCT. Additionally, the adverse effects of inaccurate power-source control on shift quality were experimentally investigated. The results revealed the primary physical factors in terms of control causing torsional driveline oscillations in clutch-to-clutch shifts. According to these observations, a detailed quantitative guide including how to generate reference trajectories for shift control is proposed, with the aim of reducing the driveline torsional vibrations without compromising the shift time. The effectiveness of the proposed control strategy was demonstrated through real-time experiments on an electrified powertrain with a DCT using a dedicated test bench. This study provides valuable insights for optimizing the shift performance of electrified vehicles—particularly for managing torsional vibrations during clutch-to-clutch shifts.