Patent ID: 8872645

Claim:
A method of estimating a road grade of a current driven road by a vehicle, the method comprising the steps of: measuring a nominal value of a vehicle operating parameter during a nominal vehicle operating condition, the vehicle operating parameter being related to a vehicle thrust power, the nominal value of the vehicle operating parameter being comprised of a nominal acceleration in a driven direction of travel, the nominal value corresponding to the nominal value of the operating parameter when the vehicle is driven on a substantially non-inclined road; storing the nominal value of the operating parameter and nominal acceleration in a memory; determining an actual value of the vehicle operating parameter during a current vehicle operating condition; measuring the vehicle acceleration in the driven direction of travel corresponding to the actual value of the vehicle operating parameter; and estimating the road grade of the current driven road as a function of a comparison between the measured acceleration value and the nominal acceleration that would be expected for the actual value of the vehicle operating parameter; wherein in the vehicle operating parameter is an axle torque; and wherein the road grade estimate is represented by the following formula: K RGE = sin ⁡ ( θ ) = τ A - τ n τ n - RL · a x g where τ A is the actual value of the axle torque at the vehicle acceleration a x and vehicle speed v on a road slope θ, τ n is the nominal value of the axle torque on a substantially non-sloping surface, RL is a road load, and g is a gravity constant.