Unified modelling and control for the power-on gear shift of a planetary transmission

Estimation of the oil hydraulic pressure for the gear-shift elements can be useful for the development of closed-loop control of the automatic transmission fitted to a heavy off-highway vehicle for a good gear-shift quality, to reduce the dissipated energy and the vehicular shift jerk in complex working conditions. The unified dynamic model for a three-degree-of-freedom planetary automatic transmission is presented, and the power-on upshift from first gear to second gear is considered as an example. The unified model is more efficient than the conventional model for the dynamic analysis; furthermore, it provides a computational method for the inertia of the transmission when in gear. From a phased characteristic analysis, real-time estimation of the oil pressure for the gear-shift elements in the sliding process, i.e. the torque phase and the inertia phase, is addressed; then the improved control scheme for the power-on upshift from first gear to second gear is developed and validated using a heavy off-highway vehicle equipped with a high-power full-range speed-regulating diesel engine. The experimental results show that the model-based oil pressure estimation is able to reflect the dynamic characteristics of the system in changing conditions, and the corresponding control strategy can improve the gear-shift quality and the vehicular performance effectively.