A method of controlling a continuously-variable drive train of a motor vehicle, said drive train comprising an engine unit having an outlet shaft driving a wheel shaft via a variable-speed transmission adapted to modify a ratio of a speed of rotation of the wheel shaft and of the engine outlet shaft in a continuous manner, in which method, a unit time interval (t1) is defined and over each unit time interval the following steps are performed:
- estimating a value of an acceleration control variable (P1);
- estimating a value of a vehicle speed (V);
- estimating a value of a speed of rotation (ω) of the engine outlet shaft;
- and
- controlling the speed of rotation (ω) of the engine outlet shaft as a function of said estimated values (P1, V, ω);
- and
- wherein said control is performed by implementing the following steps:
- determining a mode of operation from amongst a permanent mode and a transient mode, as a function of a set of variables comprising said estimated values (P1, V, ω);
- and
- correcting the value of the speed of rotation (ω) of the outlet shaft in such a manner that:
- if the mode has been determined as being the permanent mode, then a moving average (L′) of a gear ratio (L) over a period (T) of a plurality of unit time intervals (t1) lies between a first threshold value (S1) that is negative and a second threshold value (S2) that is positive;
- and
- if the mode has been determined as being the transient mode, then said moving average (L′) of the gear ratio (L) lies outside the range of values defined by the first and second threshold value (S1, S2),
- wherein a slope of a road is estimated and the set of variables includes the estimated value for the slope, and
- wherein a mode-determination period is defined, and it is determined that the mode of operation is transient mode in at least one of the following circumstances:
- over said mode-determination period, a variation in the speed value (V) and a variation in the slope value are, in absolute value, less than respective predetermined threshold values, and a variation in a value of the acceleration control variable is, in absolute value, greater than a predetermined threshold value;
- over said mode-determination period, the variation in the value of the acceleration control variable and the variation in the value of the slope are, in absolute value, less than respective predetermined threshold values, and the variation in the speed value is, in absolute value, greater than a predetermined threshold value;
- and
- over said mode-determination period, the variation in the value of the acceleration control variable (P1) and the variation in the value of the speed variable (V) are, in absolute value, less than respective predetermined threshold values, and the variation in the slope value is, in absolute value, greater than a predetermined threshold value,
- enabling sensations of skidding, variations in engine speed, and noise characteristics of the engine to be brought close to those corresponding to drive trains with manual gearboxes.