Verification of hybrid operation points
This thesis is an approach to improve a two-mode hybrid electric vehicle, which
is currently under development by GM, with respect to fuel consumption. The
study is not only restricted to the specific two-mode HEV but also presents results
regarding parallel as well as serial HEV’s.
GM whishes to verify if the online-based controller in the prototype vehicle
utilizes the most of the HEV ability and if there is more potential to lower the fuel
consumption. The purpose is that the results and conclusions from this work are
to be implemented in the controller to further improve the vehicle’s performance.
To analyze the behavior of the two-mode HEV and to see where improvements
can be made, models of its driveline and components are developed with a focus
on losses and efficiency. The models are implemented in MATLAB together with
an optimization algorithm based on Dynamic Programming. The models are validated
against data retrieved from the prototype vehicle and various cases with
different inputs is set up and optimized over the NEDC cycle. Compensation for
cold starts and NOx emissions are also implemented in the final model.
Deliberate simplifications are made regarding the modeling of the power split’s
functionality due to the limited amount of time available for this thesis.
The optimizations show that there is potential to lower the fuel consumption
for the two-mode HEV. The results are further analyzed and the behavior of the
engine, motors/generators and battery are compared with recorded data from a
prototype vehicle and summarized to a list of suggestions to improve fuel economy.
Simon Gidlöf and Otto Dunbäck
2009
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