Patent ID: 8554430

Claim:
A method for performing downshifts when driving uphill on a vehicle including an automatic transmission that includes change laws to impose changes to a lower gear based on preestablished downshift curves of the change laws, the method comprising: comparing by an automatic transmission control computer an acceleration a est (C m-max ) that can be reached at a maximum torque on a current gear to an acceleration threshold needed to maintain a current speed of the vehicle; and changing a gear ratio of the transmission to the lower gear by the automatic transmission control computer independently of a gear set point established by the change laws, when the acceleration a est (C m-max ) that can be reached at the maximum torque on the current gear is less than the acceleration threshold needed to maintain the current speed of the vehicle, wherein the acceleration a est (C m — max ) that can be reached at the maximum torque is estimated by a relationship of: a est ⁡ ( C m_max ) = a mes + 1 M ⁢ C r ⁡ ( C m_max ) - C r ⁡ ( C m ) r , in which a mes is measured acceleration of the vehicle, M is weight of the vehicle, C r (C m — max ) is torque on the wheel corresponding to maximum engine torque, C r (C m ) is torque applied to a wheel corresponding to current engine torque, and r is radius of tires of the vehicle.