Patent ID: 8892315

Claim:
A method of controlling engine speed error in a motor vehicle powertrain comprising an engine which drives at least one vehicle wheel through a transmission which provides a continuously variable ratio, the transmission being constructed and arranged to exert upon the engine a controlled loading torque and to permit the transmission ratio to vary in accordance with resultant changes in engine speed, so that engine acceleration results from application of a net torque, which is the sum of the loading torque and an engine torque created by the engine, to the inertias referred to the engine, the method comprising, in a feedback loop: determining the engine speed error as a difference in a current engine speed and a predicted engine speed, supplying the engine speed error to a closed loop controller which establishes a control effort, which is a correction to the net torque required to reduce the engine speed error, determining when the control effort can be achieved by adjustment of a loading torque without a deviation beyond a threshold amount of torque at the driven wheel requested from a driver, and adjusting the loading torque to achieve the control effort, when adjustment of the loading torque alone results in the deviation beyond the threshold amount of torque at the driven wheel requested from the driver, establishing an allocation of the control effort between (i) adjustment of the engine torque and (ii) adjustment of the loading torque to achieve the control effort, and adjusting one or more of the engine torque and the loading torque based on the allocation of the engine toque and the loading toque to achieve the control effort.