Patent ID: 7680578

Claim:
A system for determining a gradient of a road on which a vehicle drives, comprising: a linearization unit; a sum unit; and a state space model and observer unit, wherein the sum unit sums up wheel forces in a forward/backward direction, which are applied to respective wheels of the vehicle, to calculate a total sum wheel force, and the linearization unit comprises: an air resistance calculation unit for calculating an air resistance force based on a velocity of the vehicle using a non-linear approximation equation; a rolling resistance calculation unit for calculating a rolling resistance force based on the velocity of the vehicle using the non-linear approximation equation; and a subtraction unit for subtracting the air resistance force and the rolling resistance force from the total sum wheel force to calculate a linearized total sum force, and wherein the state space model and observer unit comprises: a state space model for applying a method of linear control theory to the total sum force; and an observer unit for calculating the gradient of the road based on a velocity difference between a modeled velocity of the vehicle calculated based on the linearized total sum force using the state space model, and an actually measured velocity of the vehicle.