Closed loop control of shifting clutch actuators in an automatic speed change transmission

A method of controlling hydraulic shift clutch actuators in an automatic speed change power transmission of the type having an electronic controller (TCU) for energizing a solenoid operated valve to control each hydraulic clutch actuator. A pressure sensor is disposed to sense the hydraulic pressure (P s ) to each clutch actuator and provides an electrical signal to the TCU which also receives a clutch pressure command signal (P c ) from the vehicle powertrain computer. The TCU computes the differential P = P c - P s and determines the valve energization current I E from known relationships between P and the percentage of maximum valve current and repeats the process in real time to adjust I E until P is negligible.