Method for preventing an engine from stalling using an estimate of the rotatable speed of said engine

A method for preventing a main engine (2) of a vehicle (1) from stalling, said main engine (2) being an internal combustion engine and having pistons (2a to 2d) which each perform a cycle in a cylinder to rotate a crankshaft driving a primary drive shaft (6), the vehicle (1) also comprising an auxiliary electric motor (4) for assisting the main engine (2) by means of two pulleys (8a, 8b) and a drive belt (8c), a gearbox (7), means for measuring the rotation speed of the main engine (2), and means (9) for controlling the auxiliary motor (4), comprising calculation and information storage tools, wherein:

• using an estimate of the rotation speed of said main engine (2) for a predefined subsequent angular position of the crankshaft, said rotation speed of the main engine (2) being estimated on the basis of a prediction of the instantaneous rotation speed (V1, V2, V3) of the crankshaft, called the predicted instantaneous speed;
• defining an intervention zone (Z) between two minimum speeds (Nmin1, Nmin2) of the crankshaft at said predefined subsequent angular position, namely a higher minimum speed (Nmin1) above which the engine is considered not to be in a stall situation, and a lower minimum speed (Nmin2), below which the stalling of the main engine is considered to be inevitable;
• if the predicted instantaneous speed for the predefined subsequent angular position is in the intervention zone (Z), in which there is a risk of stalling of the engine, or below this intervention zone, starting said auxiliary motor (4) as long as said predicted instantaneous speed is below a predefined threshold, to assist the rotation of the main engine (2) so that the latter continues to rotate in the same direction.