Anti-flare method using offgoing slip speed and rate of change of slip-speed to determine pressure compensation for incoming clutch

In a control for an automatic transmission having a turbine driving an output shaft through a gearset which achieves an upshift by controllably releasing an off-going torque transmitting device for a current speed ratio and controllably applying a fluid operated on-coming torque transmitting device for a lower speed ratio by a commanded on-coming pressure, wherein the turbine is subject to flare if the on-coming pressure is insufficient when the off-going torque transmitting device is released, a method of controlling the turbine flare comprising the steps of:

• measuring turbine speed and output speed;
• determining a slip speed across the off-going torque transmitting device as the measured turbine speed less the product of the measured output speed and the current speed ratio, wherein the slip speed is a measure of flare;
• calculating a rate of slip speed change;
• when the determined slip speed is positive and the calculated rate of slip speed change is positive, calculating a proportional term based on the detected slip and a positive integral term based on the calculated rate of slip speed change;
• when the determined slip speed is above the first threshold and the calculated rate of slip speed change is less than a determined negative value, calculating a negative integral term based on the calculated rate of slip speed change;
• summing the proportional and the integral terms to form a compensation term;
• and
• correcting the commanded on-coming pressure in accordance with the compensation term.

In a control for an automatic transmission having a turbine driving an output shaft through a gearset which achieves an upshift by controllably releasing an off-going torque transmitting device for one gear range and controllably applying an on-coming torque transmitting device for a higher gear range by a commanded on-coming pressure, wherein the turbine is subject to flare if the on-coming pressure is insufficient when the off-going torque transmitting device capacity is reduced, a method of automatically shifting the transmission comprising the steps of:

• disengaging the off-going torque transmitting device by reducing its pressure according to an off-going pressure command having a progressively decreasing value to complete such disengagement;
• engaging the on-coming torque transmitting device by successively supplying it with hydraulic pressure for a predefined fill period and thereafter controlling such pressure to effect a progressive engagement of the same;
• determining slip speed across the off-going torque transmitting device and the rate of slip speed change;
• when the slip is positive and the rate of slip speed change is positive, calculating a term proportional to slip and an integral term for positive slip rate;
• calculating a compensation term by summing the proportional and the integral terms;
• and
• correcting the commanded on-coming pressure by the amount of the compensation term.