Patent ID: 7991519

Claim:
Method for operating a powertrain comprising an internal combustion engine and first and second electrical machines and an electro-mechanical transmission configured to transmit torque therebetween, the method comprising monitoring an operator torque request and a present transmission output speed; calculating a first set of motor torques output from the first and second electrical machines corresponding to operating the electromechanical transmission in a first continuously variable mode with the engine in an engine-off operating state in response to the operator torque request and the present transmission output speed; calculating a second set of motor torques output from the first and second electrical machines corresponding to operating the electromechanical transmission in a second continuously variable mode with the engine in the engine-off operating state in response to the operator torque request and the present transmission output speed; calculating a first operating cost associated with the first set of motor torques output from the first and second electrical machines; calculating a second operating cost associated with the second set of motor torques output from the first and second electrical machines; selecting one of the first and second continuously variable modes as a preferred operating mode based upon the first and second operating costs; and controlling the powertrain in the preferred operating mode with the engine in the engine-off operating state in response to the operator torque request and the present transmission output speed.