Development, optimization and simulation of hybrid electric heavy duty truck with self-propelled trailer.
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The hybrid electric drivetrain has significant ability to reduce fuel consumption and increase the efficiency. The application of this type of drivetrain has been investigated for different vehicle models. The hybridization of heavy duty vehicle and tractor and semitrailers is a recent challenge for the hybrid electric vehicle researchers. Almost 20% of the total US truck fuel is approximately consumed by tractor and semi-trailers which shows the bright potential of developing hybrid electric drivetrain in this sector. A new architecture of hybrid drivetrain for tractor and semi-trailers is investigated in this thesis. This architecture is designed to utilize maximum capability of hybrid electric tractor and semi-trailers to enhance the fuel efficiency as much as possible. This drivetrain architecture employs a self-propeller trailer so that the tractive effort is divided between the tractor and semi-trailer. The advantages of this configuration are: 1) Enabling the trailer to regenerate the braking energy as well as for the tractor, 2) Improving the longitudinal dynamic behaviour of vehicle, 3) Providing sufficient space for the battery pack, and 4) Providing the potential of torque vectoring for the trailer to improve overall stability. To study the proposed drivetrain architecture, a comprehensive model of the longitudinal dynamic of vehicle, including the drivetrain model, has been developed in SIMULINK® software. The components of the developed drivetrain model are the diesel engine, electric motor, batteries, automatic gear box, clutch and final drive unit. The model has been developed using the specifications of commercially available sub-components. IV The braking energy analysis for different standard driving cycles has been conducted to demonstrate the capability of the proposed drivetrain in recapturing the braking energy and improving the efficiency of the drivetrain. The Power Management System (PMS) which controls the power flow in the system between different propulsion sources has been designed using the fuzzy logic control theory. The PMS ensures that the diesel engine, the tractor’s electric motor and the trailer’s electric motor being utilized in an efficient manner. The PMS consists of the braking controller together with the drivetrain controllers of the tractor and that of the trailer. The sizing of the drivetrain components has been optimized using multi-objective optimization theories. The objectives of the optimization have been the price of the drivetrain, fuel consumption and acceleration time which all are the function of the size of the drivetrain components. Finally, computer simulations have been conducted on different standard driving cycles in order to evaluate the efficiency and fuel consumption of the proposed hybrid drivetrain architecture. Results obtained demonstrate the advantage of proposed drivetrain in comparison with the non-hybrid and typical hybrid drivetrain for heavy duty vehicles. In addition, economic analysis has been performed to demonstrate the capability of the proposed system in fuel saving.