A research on power-on downshift control for automatic transmission

Though the driving torque of transmission is trivial or even zero in the downshift process of practical driving for majority vehicles, but in the condition of full load hill climbing for heavy-duty vehicles, power-on downshift is often necessary. Accordingly, the downshift control without power interruption for heavy-duty vehicles is studied in this paper. Firstly the model for powertriain system is set up and a control scheme for the power-on downshift process of automatic transmission is proposed based on a dynamics analysis of downshift process. Then with a constant angular acceleration of turbine shaft in the inertia phase of shifting process as reference model, an adaptive control strategy is worked out for enhancing its robustness. Finally a real vehicle hill climbing test with full load is conducted. The results show that power-on downshift control can effectively enhance the shifting quality and driving performance of vehicles.