US Patent 7912617 Air purge method for a rotating clutch

A method for controlling trapped air in a clutch of an automatic clutch-to-clutch transmission includes, calculating a pulse on time based on a clutch volume and adaptive convergence. A pulse off time is calculated based on a temperature of transmission fluid. A pulse number is calculated based on the temperature of transmission fluid. A maximum pressure is commanded to the clutch based on the pulse on time and a minimum pressure is then commanded to the clutch based on the pulse off time. A pulse counter is incremented when the pulse off time expires. The steps of commanding maximum pressure, then commanding minimum pressure, and incrementing the pulse counter are repeated until the pulse counter equals a desired pulse number.