The main difficulty in controlling combustion engine start-up comes from its changing behaviour from load to motor. In the context of hybrid power trains considered here, the electric motor used for start-up is more powerful than a traditional starter. In order to get a robust control of the crankshaft speed, we propose to take inspiration from redundant control as formulated in the aeronautic domain (Härkegard, 2003), (Härkegard and Glad, 2005), (Buffington et al., 1996), (Maciejowski, 1997), by considering that the engine and the electric motor are redundant torque providers. Despite that the engine is the primary torque provider, it will be systematically seen as the failing actuator during the start-up stage. Therefore, the electric motor has to compensate its deficiency.