Date of Award


Degree Name

Master of Science in Engineering


Mechanical and Aerospace Engineering


Mechanical and Aeronautical Engineering

First Advisor

Dr. Jennifer Hudson

Second Advisor

Dr. Richard Meyer

Third Advisor

Dr. Koorosh Naghshineh


Optimization, ratio scheduling, transmission, automotive powertrain, efficiency

Access Setting

Masters Thesis-Open Access


A transmission ratio schedule is developed to optimize the fuel consumption for an automotive continuously variable transmission (CVT) connected to an internal combustion engine (ICE). Although the optimal operating line (OOL) generated from an engine brake specific fuel consumption (BSFC) map can be used to generate a CVT ratio schedule that yields maximum engine efficiency, it was found that OOL-based CVT ratio scheduling does not necessarily offer the best fuel economy because optimal CVT efficiency does not always correspond to OOL tracking. To develop a CVT ratio schedule that can offer the best fuel economy, a novel ratio-scheduling methodology is proposed in this paper. The methodology uses an empirical approach to minimize fuel consumption by considering engine efficiency, CVT efficiency, and requested vehicle power. The proposed CVT ratio scheduling methodology has been simulated using the various portions of the FTP-75 (Federal Test Procedure) cycle. Simulation results show that a significant improvement of engine-CVT overall fuel economy gain is achieved when using the proposed ratio scheduling methodology compared with the case where OOL operation is assumed to yield the highest combined engine-CVT efficiency.