Optimal Gear Shift Control of Two-Speed Dual-Clutch Transmission in Electric Vehicle for Smoothness and Friction Loss Reduction

Abstract

An optimal shift control strategy for electric vehicles with the two-speed dual-clutch transmission is proposed to reduce the vehicle jerk and friction work during gear shift. The dynamic model of the powertrain considering the stick–slip friction of clutch is built. The developed control scheme is divided into two stages. For the upper level control, a finite-time linear quadratic regulator (LQR) is designed to optimize the target trajectories of torque and speed of motor and clutch by integrating both jerk and friction work in the cost function. Considering that the clutch torque is necessary for calculating the target trajectories but cannot be measured directly, the Kalman filter is employed to estimate the clutch torque. For the lower level control, a combination of torque feedforward and speed feedback controller is constructed to control the motor torque and clutch pressure. To validate the effectiveness of the proposed strategy, comparisons with the strategies based on the polynomial method and unsmooth LQR are carried out. Simulation results and hardware-in-loop test reveal that the jerk and friction work are both reduced, indicating better shift performance.