METHOD OF ADAPTIVE CONTROL FOR CLOSED THROTTLE DOWNSHIFT IN AN AUTOMATIC TRANSMISSION

摘要

In an automatic transmission, clutch-to-clutch closed throttle downshifting is controlled by filling the on-coming clutch at a maximum pressure command for a set period while commanding the off-going clutch pressure to a low value and exhausting the off-going clutch before the end of the fill period. At the end of the fill period the on-coming pressure is set to an initial value and then ramped up until turbine speed is pulled up due to off-going clutch slippage. Then a closed-loop profile control period starts wherein the slip of the on-coming clutch is measured and controlled to a slip profile. When synchronization of the on-coming clutch is detected, maximum pressure is commanded. Parameters for controlling the quality of a shift such as on-coming clutch initial pressure and on-coming clutch fill time are automatically adjustable during vehicle use to correct shift aberrations which degrade shift quality.