Patent ID: 7143851

Claim:
A method for operating a wheel drive system of a hybrid vehicle, the hybrid vehicle having primary and secondary power sources, a power transfer unit adapted to drive a vehicle wheel and having a plurality of gear ratios, an electrical machine coupled to the primary power source and the power transfer unit and configured to be powered by the primary and/or secondary power sources, and a brake system adapted to inhibit rotation of the vehicle wheel when a brake pedal is actuated, the method comprising: initiating a start sequence for the primary power source if the vehicle is stationary and the brake pedal is released, the start sequence including driving the primary power source with the electrical machine to attain a target speed; determining a speed adjustment value based on an amount of vehicle acceleration requested by a driver if a gear ratio of the power transfer unit is selected and the primary power source is not started; adjusting the target speed based on the speed adjustment value; and modifying output of the electrical machine to maintain the target speed.