Study On Shift Quality Control Of Wet Dual Clutch Transmission

Dual Clutch Transmission(DCT)have been widely concerned due to the advantages of comfortable shift,low production cost,compact structure,light weight,as well as high transmission efficiency.Since most transmissions made in China are manual transmissions,it is convenient for designing the high performance DCT.Currently,research of DCT is still in its infancy in China,so it is important to investigate the related technology of DCT.Furthermore,it is an important opportunity and well challenge to improve the status in the field of automatic transmission in the world.The shift quality control plays a key role in the development of high-performance DCT.For the purpose of improving the shift quality,the control strategy for clutch pressure during shift process was put forward,which was verified by the simulation of up-and downshift processes.The main contents of the paper are as the follows.(1)The development process and the working principle of wet DCT have been introduced.And the current research status of the control technology of the shifting quality has also been summarized.(2)On the basis of building the dynamics model,the shift process has been analyzed.The evaluation indexes of shift quality have been determined.Furthermore,the factors affecting shift quality have been analyzed.(3)The control strategy of engine during shift process of DCT have been drawn up.Through the analysis of the states of clutch during shift process,the control strategies of changing pressure and equal pressure during different shift processes have been put forward.The mathematics model of the clutch pressure control system of DCT has been established,which including the model of clutch valve,the model of hydraulic cylinder,the model of hydraulic pressure sensor,etc.,and the stability analysis has been carried out.Based on the study of the transmission torque in different gears,the target pressure of clutch have been determined for every shift process.The fuzzy controller of clutch pressure and the PID controller of speed of engine have been designed.(4)With BP neural network structures,the model of the engine torque has been built,and then,the optimal dynamic shift schedule has been designed.The simulation model of shift process including the engine module,the DCT shift control module,the clutch pressure control module,and the vehicle longitudinal dynamics module,has been established using MATLAB/Simulinj/Stateflow platform.Using jerk and friction work as evaluation indices for shift quality,the strategy of changing pressure has been compared with that of unchanging pressure.The simulation results show that:the fuzzy controller can make the actual oil pressure of the hydraulic cylinder trace the target oil pressure during the shift process;and both the shift jerk and friction work produced under the strategy of changing oil pressure are less than that produced under equal pressure strategy during all up-and downshift processes of DCT.