Clutch control strategy for shifting a transmission

A method of shifting a planetary transmission, the transmission being configured for a plurality of gear states including a first gear state and a second gear state, the transmission having a lever configuration including a plurality of nodes that represent rotation elements of the transmission, the plurality of nodes including in the first and second gear states an input node, an output node, a first node configured for engagement with a first coupling member in the first gear state, and a second node configured for engagement with a second coupling member in the second gear state, the first node having a first lever position in the first gear state and a second lever position in the second gear state, the transmission being capable of clutch-to-clutch shifting from the first gear state to the second gear state without engagement of a third coupling member, is the third coupling member being capable of connecting a predetermined one of the nodes to a predetermined other of the nodes during a transition from the first gear state to the second gear state so as to urge the first node from the first lever position to the second lever position, comprising:

• engaging the first coupling member in the first gear state;
• during a torque phase of the transition, initiating a disengagement of the first coupling member and an engagement of the second coupling member;
• during an inertia phase of the transition, engaging the third coupling member to connect the predetermined one of the nodes and the predetermined other of the nodes;
• and
• at a completion of the inertia phase, disengaging the third coupling member.

A controller for shifting a planetary transmission from a first gear state to a second gear state, the transmission having a lever configuration including a plurality of nodes that represent rotation elements of the transmission, the plurality of nodes including in the first and second gear states an input node, an output node, a first node configured for engagement with a first clutch in the first gear state, and a second node configured for engagement with a second clutch in the second gear state, the first node having a first lever position in the first gear state and a second lever position in the second gear state, the transmission being capable of clutch-to-clutch shifting from the first gear state to the second gear state without engagement of a third clutch, wherein the third clutch is capable of connecting a predetermined one of the nodes to a predetermined other of the nodes during a transition from the first gear state to the second gear state so as to urge the first node from the first lever position to the second lever position, the controller containing an instruction set, the instruction set executable to:

• engage the first clutch in the first gear state;
• during a torque phase of the transition, initiate a disengagement of the first clutch and an engagement of the second clutch;
• during an inertia phase of the transition, engage the third clutch to connect the predetermined one of the nodes and the predetermined other of the nodes;
• and
• at a completion of the inertia phase, disengage the third clutch.