Adaptive clutch control of a closed-throttle downshift

摘要

A closed-throttle downshift control adjusts engine torque to raise the input speed of a transmission to the synchronous speed of the target speed ratio, and adaptively adjusts clutch control parameters to coordinate the off-going clutch release and the on-coming clutch apply, and to complete the shift with minimum driveline torque disturbance. A primary on-coming clutch control fills the on-coming clutch and then raises the on-coming pressure when the input speed reaches the synchronous speed of the target speed ratio. If input synchronization cannot be maintained, a contingent control increases the on-coming clutch pressure to gradually re-establish the input speed synchronization and thereupon engage the on-coming clutch to complete the shift. The fill time or the maintenance pressure of the on-coming clutch is adaptively decreased for reduced driveline disturbance in subsequent shifts of the same type if the output shaft jerk during the primary control exceeds a threshold. Additionally, the fill time or the maintenance pressure of the on-coming clutch is adaptively increased based on an integral of the on-coming clutch slip for reduced dependence on the contingent control in subsequent shifts of the same type if an integral of the on-coming clutch slip during the contingent control exceeds a threshold amount.