System and method of executing a double transition shift in a transmission with transitioning clutch having opposite clutch slip and torque carrying directions

A transmission system comprising:

• an input member;
• an output member;
• a gearing arrangement;
• a plurality of selectively engageable clutches engageable in different combinations to establish a plurality of different gears through the gearing arrangement, the different gears having different torque ratios of torque of the output member to torque of the input member;
• wherein said plurality of different clutches include a first clutch, a second clutch, a third clutch, and a fourth clutch;
• wherein the first clutch and the second clutch are engaged and the third clutch and the fourth clutch are not engaged in one of said gears, and the first clutch and the second clutch are not engaged and the third clutch and the fourth clutch are engaged in another of said gears so that a shift from said one of said gears to said another of said gears is a double transition shift;
• wherein one of the four clutches has a clutch slip direction relative to input member rotation direction in said one of the gears and an opposite clutch torque direction relative to input member torque direction in said another of the gears;
• a controller operatively connected to each of the selectively engageable clutches;
• wherein the controller has a processor configured to execute a stored algorithm that:
• determines whether a commanded shift is for the double transition shift;
• calculates clutch torques for at least some of the four clutches based on at least some of output member torque, input member torque, input member acceleration, and clutch slip acceleration if the commanded shift is for the double transition shift;
• controls torque at the four clutches during the shift according to said calculated clutch torques to ensure that said one of the four clutches does not provide reaction torque during the shift unless slip across said one of the four clutches is zero or in the clutch torque direction relative to input member torque direction of said another of the gears.