Date of Award


Degree Name

Master of Science in Engineering


Mechanical and Aerospace Engineering

First Advisor

Dr. Jennifer Hudson

Second Advisor

Dr. Richard Meyer

Third Advisor

Dr. Koorosh Naghshineh

Fourth Advisor

Dr. Zach Asher


power-split hybrid electric vehicle, optimal gear ratio, vehicle modeling, forward-looking, optimal energy management

Access Setting

Masters Thesis-Open Access


Increases in vehicle demand and fossil fuel consumption are major contributors to environmental problems, such as air pollution and climate change. This has led to research on alternative, energy-efficient vehicle technologies. Automobile users are now preferring comfortable vehicles with minimal fuel consumption and with more efficient engines. Hybrid cars are becoming common because of their advantage of running cleaner and with better gas mileage. A hybrid car runs on the power of both an electric motor and a gasoline engine. This mechanism helps cut fuel consumption and conserve energy. An additional advantage is a regenerative braking system that helps recharge the battery, which ultimately reduces load on the engine and hence produce lower emissions. In this thesis, components of hybrid electric vehicles are defined and a computational model of a typical hybrid system is developed. Modeling and simulation of these components is done in the Matlab/Simulink environment. This thesis underscores the HEV model that can be used in future and the importance of optimized powertrain components, especially the planetary gear ratio and its impact on vehicle performance and fuel economy. The planetary gear ratio ensures smooth transmission, propulsion capacity, acceleration, and fuel economy. This thesis investigates the effect of different gear ratios on fuel economy for the US06 and FTP75 drive cycles and proposes a strategy for optimizing gear ratio to maximize fuel economy without compromising vehicle drivability. The study presented in this thesis also emphasizes battery stability and optimal energy management at different gear ratios. The forward-looking, velocity-driven, power-split model developed in this study highlights the importance of gear ratio in engine operation and also ensures that generator does not overrun in the process.