Shift Quality Improvement through Integrated Control of Dual Clutches Pressure and Engine Speed for DCT

The clutch-to-clutch gear-shift process of dual clutch transmission (DCT), which consists of the overlapping of the engagement of the incoming clutch and the disengagement of the outgoing clutch, is a vital stage for the shift quality improvement. The paper investigated an integrated control strategy for the gear-shift process that takes into account the influences of oil pressure of dual clutches and engine speed on shift quality. Firstly, the evaluation indices for the shift quality of DCT were summarized, and the factors affecting the shift quality were analyzed. Secondly, an integrated control strategy for dual clutches pressure and engine speed was proposed. Through analyzing the states of clutch in the gear-shift process and the desired traction torque for different gears, the strategies of variable oil pressure and invariable oil pressure were determined for every gear-shift process. Furthermore, a PID controller for engine speed and a fuzzy controller for clutch pressure were developed respectively. Finally, the simulation model for the gear-shift process of a wet-type DCT was built, and taking the shift jerk and the friction work as evaluation indices for the shift quality, the variable pressure strategy has been compared with the invariable pressure strategy via simulation experiments. Simulation results show that the fuzzy controller can make the actual clutch pressure trace the target pressure precisely in the gear-shift process and both the shift jerk and the friction work produced with the variable pressure strategy are less than those produced with the invariable pressure strategy for all up- and downshift processes of DCT.