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Abstract



Parallel Hybridization of a Heavy-Duty Long Hauler


Long haulage of heavy-duty trucks weighing over 15-ton stands for nearly 50% of the fuel consumption among trucks, making them the most fuel consuming category. This indicates the potential benefits in improving the fuel efficiency for said category. Hybridization is one possible solution. Hybrid vehicles are vehicles with two or more power sources in the powertrain. Different powertrain configurations, hybridization levels and hybrid concepts are best suited for different applications. With prices for fossil fuels constantly rising hybridization is an important technology to improve fuel efficiency. Different variations of configurations and concepts enables many choices when deciding on a hybrid driveline. A simulation tool for efficiently comparing various hybrid drivelines would be a great asset when deciding on a configuration for a certain vehicle application. For this thesis the application in focus is the previously mentioned category, a heavy duty long hauler weighing 36-ton. The modeling approach used for the simulation tool is called quasistatic modeling or "backward modeling". This name comes from, based on a chosen drive cycle, the resisting forces which act on the vehicle can statically be calculated at each step from the velocity profile. The required power to drive along the drive cycle can then be calculated backwards within the powertrain resulting in a fuel consumption for the combustion engine. For this the free QSS-toolbox for Matlab Simulink has been used as a base and modified when needed. The configuration chosen to be implemented is a parallel electric hybrid and was chosen for its good characteristics for the type of driving highways provide. For this configuration two types of controllers are used, one being an Equivalent Consumption Minimization Strategy controller and the other a simple, rule based heuristic controller. The results for both controllers show small benefits with hybridization of the long hauler compared with the conventional which in the long run would make bigger difference because of the large consumption in whole. A sensitivity analysis was also done showing that improving conventional vehicle parameters can be as beneficial as hybridization.

Tommie Eriksson

2015

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