Method for estimating an index representative of the frictional behavior of a vehicle on a road

A method for estimating a value representative of a frictional behavior of a vehicle being driven on a road segment, the method comprising:

• receiving, by a processor, operating parameters of a vehicle comprising at least, a value representative of an angular velocity of a driving wheel, a value representative of an angular velocity of a free wheel of the vehicle, and a dynamic characteristic of the vehicle;
• computing, by the processor, a first ratio between the value representative of the angular velocity of the driving wheel and the value representative of the angular velocity of the free wheel of the vehicle, which are acquired in a first time window during which the vehicle is moving substantially in a straight line at a first velocity in which micro-slips of a driving wheel on a roadway are liable to occur;
• computing, by the processor, a second ratio between the value representative of the angular velocity of the driving wheel and the value representative of the angular velocity of the free wheel of the vehicle, which are acquired in a second time window during which the vehicle is moving in a substantially straight line at a second velocity of the vehicle in which micro-slips of the driving wheel on the roadway are liable to not occur;
• determining, by the processor, a third ratio between the radius of the driving wheel and the radius of the free wheel based on the first ratio and the second ratio;
• determining, by the processor, a slip rate from a product of the third ratio and a fourth ratio between the value representative of the angular velocity of the driving wheel and the value representative of the angular velocity of the free wheel;
• estimating, by the processor, the value representative of the frictional behavior of the vahicle by normlizing the determined slip rate using at least the dynamic characteristic of the vehicle;
• and
• automatically controlling, by the processor, an operation of the vahicle based on the estimated value representative of the frictional behavior of the vehicle.