Patent ID: 8731753

Claim:
A control-module implemented method to control a flying engine start in a powertrain comprising an electric motor providing a propulsion torque to a transmission input shaft, an internal combustion engine, and an engine disconnect clutch selectively providing torque transfer between the engine and the motor, the method comprising: monitoring an output torque request; determining the propulsion torque to the transmission input shaft based upon the output torque request; monitoring a desired input speed; determining a synchronization speed based upon the desired input speed; determining, by a controller, a desired engine activation speed profile based upon the synchronization speed, comprising: determining a first stage wherein a compensation torque is provided from the motor to the engine through the engine disconnect clutch to accelerate the engine from a stopped state to an engine firing speed; once the engine firing speed is achieved, determining a second stage wherein the engine provides torque to accelerate the engine while simultaneously reducing the compensation torque provided from the motor to the engine; determining a third stage subsequent to the second stage wherein the compensation torque is provided to the engine by the motor to control the engine to the synchronization speed; and determining a fourth stage wherein the engine disconnect clutch is locked; and controlling the motor to provide a motor torque based upon a sum of the propulsion torque and the compensation torque.