Model-based engine torque control for power-on downshifting in an automatic transmission

Abstract

An improved engine torque control for an automatic transmission power-on downshift, wherein a dynamic model of the transmission is used to schedule both shift progression and engine torque reduction based on a desired trajectory of the transmission input shaft during the shift and the driver torque demand. The shift is initiated with the off-going clutch by using the dynamic model to conform the input speed to the desired trajectory, and the torque reduction is initiated based on an estimate of the time to synchronization relative to an expected control delay so that the torque reduction occurs when the input speed reaches synchronization. An appropriate torque reduction amount is calibrated for a specified driver torque demand, and in operation, the amount of torque reduction for a given shift is determined based on the current driver torque demand and a detected deviation of the desired trajectory from a nominal trajectory corresponding to the specified driver torque demand. Aberrant conditions, including failure of the input speed to reach synchronization and input speed flaring are detected and used to modify the engine torque control so that the shift is completed in a timely manner. Using the dynamic model to scheduling the torque control achieves more consistent shift feel and improved adaptability to different powertrain and vehicle-type configurations, and reduces the number of calibrated parameters requiring adaptive correction.

Dependencies are inferred from the claim text.