The DCTs have increased in prevalence for achieving power uninterrupted shifting and pre-shift process significantly influences the DCTs shift quality. Research on the multistage and nonlinear characteristics of the gear preselect process is not comprehensive so that there are shortcomings such as high impact, long synchronization time and poor economy. In view of above detrimental phenomenon, control parameters optimization is conducted in order to realize fast, smooth and economic pre-shifting on the basis of analyzing the sensitivity of the factors affecting pre-shift process. Considering the engagement of sleeve, synchro ring and dog gear, the multi-body dynamics theory is applied to establish an accurate synchronizer dynamics model. Based on the model, simulations are conducted to confirm factors like sleeve mass, cone angle fluctuating the pre-shift quickness and smoothness, sorting structure parameters according to factors sensitivity. Furthermore, the formula of energy loss characteristics relating to two control parameters which are pre-shift force and pre-shift trigger time is obtained, deriving from exploring the hydraulic loss caused by pre-shift force and the drag torque energy loss created by pre-shift trigger time. The optimal synchronizer structure parameters are obtained by adopting multi-objective optimization method. Simulation results indicate the optimal control parameters improve pre-shift comprehensive performance including quickness, smoothness and economy compared with conventional scheme.

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