Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Mechanical and Aerospace Engineering

Committee Chair

Nigel N. Clark.


Increased concern about the fuel economy of and emissions from automobiles has led to interest in the use of hybrid electric powertrains and the introduction of several production vehicles in both heavy-duty and light-duty applications. Hybrid electric vehicles (HEVs) use a combination of electric motor(s) and another power source such as an internal combustion engine (ICE) or fuel cell. While these vehicles show great potential for use in a wide variety of driving situations, the optimization of components and control strategies is quite complex.;In this thesis, Class 2B, Class 6, and Class 8 vehicles are determined by averaging a variety of actual vehicles from each class and are simulated in Microsoft Excel over a variety of driving cycles to attempt to optimize their design and control. The drive cycles are modified to represent realistic expectations of the dynamic performance of vehicles from each class. Two types of hybrid powertrains are simulated. The series HEV is propelled solely by electric motors with energy coming from batteries and an alternator driven by an ICE. The parallel HEV is propelled by both electric motors and an ICE with charging-while-driving capabilities. The model is based on power requirements for each vehicle class and addresses concerns such as engine, battery, and driveline efficiencies. The control strategy forces the engine to run at a fixed percentage of the power required at the wheels plus or minus a battery state of charge correction factor.;Fuel economy increases of 100 to 150 percent were seen for Class 6 and 8 vehicles on transient cycles while 10 to 20 percent increases were seen on more constant speed cycles. The Yard cycle, a low average demand, highly transient cycle, was shown to be particularly suited to HEVs.