Engine coordinated control for automatic transmission downshift process

In order to improve the shift quality and extend the durability of the clutch, the engine coordinated control for gear downshifts is studied in this paper. A dynamic model of 2-1 shifting process is built using the Lagrange method. Subsequently, by analyzing stages of the shifting process, the quantitative relationship between the input torque and the clutch friction torque of ideal gear shifting has been obtained, and the ideal control trajectories of clutch pressure are proposed. The output torque observer is designed, moreover, the coordinated powertrain control strategy for gear shifting has been provided. The experimental results show that through coordinated engine torque control, the shift jerk and the friction work during downshift inertia phase can be reduced significantly; what´s more, the shift quality of power-on downshifting can be improved by the closed-loop control of turbine speed.