Shift Control And Dynamic Simulation Of Wet-type Dual Clutch Transmission For Electric Vehicles

With the improvement of the economic and power requirements of electric vehicles,dualclutch transmissions have been widely discussed and researched in the field of pure electric vehicles.Due to the characteristics of large transmission torque and smooth engagement process,the wet dual-clutch transmission has significant advantages in medium and large vehicles.However,due to the non-linear characteristics of the wet clutch,the transmission system still has the difficulty that the shifting is not easy to control.The research on the control of the wet dual-clutch transmission of electric vehicles has important research significance to promote the domestic independent research and development of the powertrain and transmission system of electric vehicles.Based on the analysis of the power transmission system of the wet dual-clutch transmission,the traditional open-loop control strategy is improved,and a closed-loop control method with unscented Kalman filter real-time torque observation as an input item is proposed.In the simulation analysis,the differences between the two control strategies are compared,and the feasibility of the real-time torque observation scheme is discussed.Finally,the proposed shift control strategy is verified by the hardware-in-the-loop testing.(1)The multi-degree-of-freedom torsional vibration mechanics model of the transmission system is established,and a reduced-order model based on the balanced truncation method is derived.Among them,in the process of shifting,the motor side three-degree-of-freedom model and the driving wheel side ten-degree-of-freedom model are derived;in the gear engagement state,the twelve-degree-of-freedom model of the transmission system is derived.And through the balanced truncation method of the linear model,a high-precision reduced-order model is obtained.(2)A dynamic model of the wet clutch engagement process is established.Based on the average flow model of the transmitted torque of the wet clutch and the response characteristics of the solenoid valve and the hydraulic cylinder under the control current,the engagement process of the wet clutch is analyzed and modeled,which provides a basis for the formulation of the control strategy.(3)The traditional shift control strategy has been optimized.A torque observation scheme based on unscented Kalman filtering and a clutch control method based on segmented PID are successively proposed to control the non-linear process of the wet dual-clutch transmission shifting.In the torque observation scheme,considering the large range of commercial vehicle weight changes,real-time estimation of driving resistance is increased.The solution can obtain the transmission torque of the two clutches in real time without adding a torque sensor,and provides a reliable feedback signal for shift control.The segmented PID algorithm solves the difference in the characteristics of the wet clutch at different stages of engagement.(4)A software/hardware-in-the-loop platform is established to verify the control strategy proposed in this thesis.In the hardware-in-the-loop test experiment,the control algorithm part is loaded with the stm32 control chip,and the dynamic model part is loaded in the hardwarein-the-loop industrial computer NI PXI equipment,and the hardware is performed with the structure of the upper computer-industrial computer-controller.Simulation analysis in the loop.A reliable hardware-in-the-loop platform is built for the dual-clutch transmission power transmission system,and the control strategy proposed in this paper is verified.