Design And Control Of Decentralized Actuator Based On Wet Dual Clutch Transmission

Transmission is a key component connecting power source and driving wheel,and its performance directly affects the overall performance of vehicle dynamics,economy and comfort.In recent years,dual-clutch transmission(DCT)has attracted widespread attention worldwide due to its high transmission efficiency,uninterrupted power during shifting,and good production inheritance.Wet dual clutch has the advantages of good heat dissipation performance,large torque capacity and long service time,so it has greater development potential compared with the dry dual clutch.The traditional wet dual clutch transmission adopts the centralized valve-controlled actuator scheme,which makes the wet DCT hydraulic system low efficiency and serious power loss.Therefore,it is of great theoretical significance and engineering value to carry out research on the design theory and control method of new actuators to improve the energy efficiency and control capability of the system,promote energy saving,carbon reduction and product autonomy.This research is supported by the National Natural Science Foundation of China’s key project "DCT Intelligent Control and Evaluation Method Considering Service Performance,Driving Behavior and Driving Environment"(Project No.U1764259)and "Design Theory and Control Method of a New type Power-cycling Continuously Variable Transmission System"(Project No.51875055).Aiming at the low efficiency of traditional DCT hydraulic system,a new configuration of decentralized pump-controlled hydraulic actuator and its forward design method are proposed.Taking the new pump controlled direct drive actuator as the research object,a systematic control method is designed for the clutch oil filling process.Based on the new actuator,in order to realize the full life cycle of the transmission,considering the effect of service time on the friction characteristics of the clutch,the DCT vehicle starting and shifting control strategy is studied.The main contents of this paper are as follows:(1)The structural mechanism and system efficiency of centralized valve-controlled hydraulic system,variable displacement gear pump hydraulic system and dual-pump hydraulic system are qualitatively analyzed.The optimization idea of separating the high-pressure low-flow hydraulic subsystem from the low-pressure high-flow hydraulic subsystem is revealed,and a decentralized pump-controlled hydraulic architecture is proposed.By analyzing the power loss in each stage of the hydraulic system driving process,the efficiency models of the centralized valve-controlled hydraulic system and the decentralized pump-controlled hydraulic system are established.The efficiency of the two hydraulic systems is compared under NEDC driving cycle,and the superiority of the new hydraulic system in energy saving is verified by quantitative analysis.The simulation results show that the new configuration reduces the power loss by 73% and increases the energy efficiency by 20% compared with the traditional configuration.(2)A forward matching design method is proposed for the new decentralized pump-controlled hydraulic actuator.According to the control strategy,performance index,clutch structure parameter and vehicle structure parameter,the performance boundary value of each hydraulic subsystem is defined.The performance parameters such as system pressure and flow are obtained by the boundary values of the performance requirements of each hydraulic subsystem.And complete the hydraulic system matching design based on the performance parameters.(3)The working principle of the new pump-controlled direct-drive actuator is analyzed,and the dynamic model of each stage of the clutch oil filling process is established.Aiming at the control problem of clutch precharging stage,singular perturbation theory is introduced to decouple the mechanic-liquid coupling system into an integral series system,and the model order reduction is realized.Based on the reduced order model,the motor speed reference trajectory is obtained by using the active disturbance rejection control algorithm.In order to track the speed reference trajectory and consider the influence of system parameter perturbation and load time variation,a speed-loop linear active disturbance rejection controller is designed.Aiming at the clutch oil-filling stage control problem,a linear active disturbance rejection control method is proposed to realize the real-time tracking of the reference trajectory,and the known information of the controlled object is input into the ESO as compensation,so as to improve the identification accuracy of the extended observer and improve the control accuracy.(4)The K-means clustering algorithm is used to classify the selected data for starting intention,and SVM is used to construct the starting intention recognizer for small sample data,so as to realize the accurate and fast recognition of starting intention.The driveline dynamics model of DCT starting process is established,and the friction transmission performance and attenuation characteristics of wet clutch are studied.The friction coefficient is estimated by dual extended Kalman filter algorithm.Based on the estimated friction coefficient,an adaptive control strategy of "front-end optimization +back-end compensation" is proposed to achieve the consistency of control effect during the full life cycle of DCT.The front-end optimization adopts the pseudo-spectral method to obtain the optimal motion trajectory and control trajectory of the starting process under different starting intentions.A back-end compensator is designed by the ADRC algorithm to track the desired trajectory of the driven disc,and the effectiveness and robustness of the strategy of "front-end optimization + back-end compensation" is verified by simulation tests.(5)The dynamic model of DCT shift process is built,and the shift process of DCT is analyzed in detail.Based on the dual extended Kalman filter,the average value of friction coefficient in the current service state is obtained,and the optimization objective function is constructed according to the jerk and friction work.The pseudo-spectral method is used to solve the numerical optimization of the torque phase and the inertia phase respectively,and the optimal motion trajectory and control trajectory of each phase are obtained.The feedback compensation mechanism is established to suppress the slight perturbation and track the reference trajectory.The effectiveness of clutch control method is verified by vehicle test.