Acceleration-based control of power-on clutch-to-clutch upshifting in an

Abstract

An event-sequenced control for power-on clutch-to-clutch upshifting of a multiple speed ratio automatic transmission. The average output shaft acceleration during the fill period of the on-coming clutch is determined and used to compute a target acceleration value for the completion of the torque phase. The initial achievement of on-coming clutch torque capacity is detected when the input acceleration momentarily becomes negative or when the output acceleration drops by a first specified percentage of the difference between the initial and target values, whichever comes first. As such point, the reduction of the off-going clutch pressure is intensified but its slippage is limited to a near-zero value. An impending completion of the torque phase is detected when the output acceleration drops by a second specified percentage of the difference between the initial and target values. At such point, the off-going clutch is fully released, and a closed-loop control of the on-coming clutch is initiated to complete the torque phase and carry out the ensuing inertia phase. Engine torque controls are employed during the inertia phase to ensure a smooth output torque transition at the end of the shift, and to reduce the energy dissipated in the on-coming clutch.