Patent ID: 7282012

Claim:
An adaptive pressure control method for a swap-shift transmission having first and second gearsets arranged in series and defining multiple overall gear ratios as power is transmitted from an engine-driven power input shaft to vehicle traction wheels, each gearset having a pressure-actuated friction element to establish selectively each of two gearset ratios, the method comprising the steps of: simultaneously controlling friction element pressure for the first and second gearsets during a swap-shift whereby friction element pressure for the second gearset is increased as friction element pressure for the first gearset is decreased during progression of the swap-shift; applying a calibrated boost pressure on the friction element for the second gearset before a start of torque transfer between the friction elements; reducing boost pressure to a starting pressure for the friction element for the second gearset; detecting an error in a starting pressure during a current shift, whereby the pressure on the friction element for the second gearset is too low to begin a shift; ramping the pressure on the friction element for the second gearset to a value needed to begin a shift; detecting the time of the pressure ramping during a current shift; and converting ramping time to a pressure adjustment for the friction element of the second gearset, thereby changing pressure ramping during a subsequent shift.