Study On Micro-slip Control Method For Wet Dual Clutch Transmission

Dual clutch transmission(DCT)has comprehensive advantages with regard to efficiency,comfort and cost,it has attracted wide attention and achieved fast development in the transmission market.As one of the key technology,clutch micro-slip control plays an active role in improving the performance of the wet DCT.However,parameter variations,model uncertainties and external disturbances exist in the transmission system,those factors will affect the clutch micro-slip state during its operation.Therefore,it is of great importance to carry out theoretical research on the control method to realize the clutch micro-slip state under different working conditions.For this purpose,studies of this thesis are as follows:According to features of the wet DCT,a driveline model and a clutch hydraulic actuator model are established in MATLAB/Simulink environment,their model accuracy are validated by experimental data,so that the proposed models can be used as the numerical simulation platform for the subsequent control method research.As the clutch touch point identification is significant for the clutch control,this thesis analyzes the clutch filling process,and identifies the pressure characteristic phase by phase via least square method,thus determines the clutch touch point within two phases of the pressure characteristic.Further more,a simple strategy is proposed to fulfill the clutch touch point adaption as well,it utilizes the mean and maximum value of the clutch slip to regulate the target filling pressure by calibration method,vehicle tests has proved the effectiveness of the strategy.For vehicle creep control,an optimal reference trajectory of the clutch slip is obtained via the LQ method without considering the system nonlinearity.Hence,the creep control is summarized as a tracking problem in view of some nonlinearities and uncertain disturbances,and a nonlinear robust controller is proposed by means of the backstepping approach to track the clutch slip trajectory.Simulation results has shown that the algorithm has high precision with anti-disturbance ability.Meanwhile,in order to achieve micro-slip on the clutch for vechicle launch,a novel controller is proposed via the pole placement method based on the clutch slip dynamics,of which the feedforward term is related to the engine and drive shaft torques,and the feeeback is formed by the comparison between the actual slip and desired micro-slip,and the switching condition for the micro-slip control is determined according to the closed-loop control system.Since the drive shaft torque can not be measured on-line,an extended Kalman filter is proposed to estimate it as an alternative solution.The proposed controller is validated by simulation works,and the results show that the clutch micro-slip is stable and robust.For gearshift,a controller is proposed via GPC method to achieve micro-slip on the clutch in the torque phase,of which the future output of the clutch slip is predicted based on a CARIMA model,the parameters of the CARIMA model is identified within the recursive least square algorithm,and its input is calculated by solving a quadratic programming problem.The simulation results has shown that the proposed algorithm is effective in clutch micro-slip control during the gearshift process,so as to avoid negative torque transmitted by the clutch.