Patent ID: 8447451

Claim:
A method of controlling operation of an electric all-wheel drive hybrid vehicle having an internal combustion engine configured to drive the vehicle via a first set of wheels through an automatic transmission, a first motor-generator configured to start the engine, and a second motor-generator configured to drive the vehicle via a second set of wheels, the method comprising: driving the vehicle solely via the second motor-generator while the engine is off; receiving a request for the engine to be started for generating a desired level of transmission output torque; determining a desired engine speed and a gear ratio in the transmission according to the desired level of transmission output torque; starting the engine via the first motor-generator for generating the desired level of transmission output torque; locking up all but one of a plurality of transmission torque transmitting devices required to be engaged for selecting the gear ratio; modulating the engagement of the one remaining torque transmitting device of the plurality of torque transmitting devices such that a torque capacity of the one remaining torque transmitting device is gradually increased; controlling the engine to generate the desired engine speed while the engagement of the one remaining torque transmitting device is being modulated; regulating the engine and the first motor-generator such that combined torque input from the engine and the first motor-generator to the transmission is approximately zero; locking up the one remaining torque transmitting device to select the gear ratio; and controlling the engine to generate the desired level of transmission output torque.