Abstract:

A pure electric vehicle’s 2-speed transmission with single friction clutch is focused. The coordinating and optimal control with two control variables is proposed for its gearshift process based on the principle of the minimum. In the torque phase, driver power demand (DPD) instead of the traditional driver torque demand (DTD) is adopted to attain constant vehicle’s acceleration. In the inertia phase, the optimal coordinating control is proposed with the torque gradient of friction disk clutch and motor as the two control variables, while with the jerk at the end of inertia phase and the friction work as the optimal objectives. Numerical method is employed to solve the constrained Bolza problem and obtain the optimal state trajectories. Besides, the shift control strategy is simulated on the Matlab/Simulink platform. The simulation results imply that the proposed optimal coordinating shift control based on the minimum principle is a feasible scheme. Through the application of shift control on the bench-test, the results indicate that the shift control strategy can effectively improve shift quality and extend the life span of the friction disk clutch.

Key words: Bolza problem, principle of the minimum, shift control strategy, automatic transmission