Optimal Operation and Control of a Hydrostatic CVT Powertrain

This paper details the optimal operation of a hydrostatic continuously variable transmission (CVT) for fuel economy and driving performance. The best overall system performance curves have been identified including a large variation in performance of a powertrain and an engine. These curves are a three-dimensional function of the engine torque, engine speed and the CVT ratio. Including the CVT efficiency in the system adds in another constrain in control scheme for optimal operation. For cruising at a given speed for each constant power requirement, the engine and the powertrain operating points can be found. The system operations for acceleration in fuel economy and performance mode are also discussed. Finally, the controller designs for both cases are presented.