CONTROL SYSTEM AND METHOD FOR A POWER DELIVERY SYSTEM HAVING A CONTINUOUSLY VARIABLE RATIO TRANSMISSION

A control system and method for a power delivery system, such as in an automotive vehicle, having an engine coupled to a continuously variable ratio transmission (CVT). Totally independent control of engine and transmission enable the engine to precisely follow a desired operating characteristic, such as the ideal operating line for low fuel consumption. CVT ratio is controlled as a function of commanded desired system performance (e.g., power or torque) and measured actual system performance, such as CVT torque output, while engine fuel requirements (e.g., throttle position) are strictly a function of measured engine speed. Fuel requirements are therefore precisely adjusted in accordance with the ideal characteristics for any load placed on the engine. Appropriate controls prevent anomalous engine and vehicle behavior, and allow for transient start-up from rest. In order to counteract the inherent tendency of the vehicle to accelerate when the accelerator pedal is released, a mechanism is provided for diminishing fuel flow to the engine by an amount proportional to the rate at which the commanded power or torque is reduced.