Unfortunately, there does not currently exist a methodology to choose the appropriate transmission ratio to take full advantage of the CVT's potential to offer both improved fuel economy and driveability. From this research, a systematic methodology was developed for choosing the optimum ratio trajectory of a continuously variable transmission in a passenger vehicle. The methodology embraces and resolves trade-offs between driveability and fuel economy via a constrained optimization problem and its solution. The ratio optimization is set in the context of an intelligent hierarchical control strategy, which is proposed as the methodology for achieving the maximum potential benefits that a CVT has to offer over standard discrete-ratio transmissions. The intelligent hierarchical controller allows additional vehicle and driving environment information to be identified and enhances the functionality and performance of the overall ratio control strategy.
Simulation results support claims of improved fuel economy and various aspects of driveability.
A vehicle powertrain model was developed as a hybrid combination of data-driven neural networks and analytical and heuristic techniques. The engine and torque converter models especially provide novel and simple solutions to complex modeling and simulation problems. These models, and the overall powertrain model are both tractable and sufficiently accurate for use in a support and testing role for the development of the CVT ratio control system. The powertrain model is fully validated with data garnered from a CVT-equipped test vehicle.