Clutch Coordination Control for Series-Parallel DHT Mode Changing

As a newly designed hybrid transmission, DHT (Dedicated Hybrid Transmission) owns the advantages of compact structure, multi-modes and excellent comprehensive performance. Compared with the traditional add-on hybrid transmission with one single motor, DHT uses one independent generator for engine starting and speed adjusting which can be largely improve the driving performance in the mode changing process. Based on the series-parallel DHT with wet clutch for power coupling, this paper firstly analyses the power coupling clutch device functionalities from the power flow viewpoint under normal and limp home condition. And for the changing process from series to parallel mode, a clutch coordination control strategy is designed by combining generator fast speed adjusting with clutch accurately pressure controlling to fulfill the fast driver intension response and clutch protection. And target torques of power sources are designed by a model-based method and two PID closed-loop algorithms are designed for controlling the clutch pressure accurately. Such strategy and algorithms are verified with vehicle test and the results show that the strategy can quickly complete the mode changing and driver intension changing with vehicle jerk within ± 10 m/s³, improving the driving pleasure with prolonging the clutch lifetime.