Description

In this thesis, hybrid electric vehicles with fuel cells as the main generation source are studied.
Within this analysis, a type of vehicle is characterized, which is an urban service bus. The operating
parameters are based on the analysis of the selected speed profiles. Besides, power profiles
are generated for the vehicle. Some profiles are chosen, such as the Buenos Aires driving cycle,
and the Manhattan driving cycle, whose characteristics of speed, acceleration, and distance are
analyzed. The speed profiles have moments when the bus brakes to stop at the respective stops,
and in some cases, during the intermediate journeys.We use the concept of regenerative braking
and propose as elements of energy storage and recovery, batteries, and supercapacitors. The
combination allows a better use of the total braking energy, due to the high power and energy
density of the supercapacitors and the battery respectively.
Once the structure and type of vehicle have been defined and its components have been modeled,
defining their power and energy capacities, the optimum scenario is sought through dynamic
programming. Taking into account different multi-objective, cost functions are proposed, which
take into account the hydrogen savings in the fuel cell and the health of the components. Results
are presented for both profiles and various cost functions, analyzing system behavior and
presenting Pareto diagrams for tuning the weights of the respective functions. Then, the EMPC
controller is designed, which in addition to the conventional criteria, takes into account the cost
of generating the elements. Several simulations are performed with the proposed models and
different efficiency values of the components. The analysis of various cost functions is also performed,
and the results are compared with dynamic programming and the behavior of the system
in the face of various sizes of prediction horizon is analyzed.
Finally, a trajectory planning is made, taking into account the number of bus stops, and taking
into account the dynamics of the bus operation. In this sense, we obtain certain maximum and
minimum speed paths from the driving profiles, which are made from the maximum and minimum
acceleration data of the driving profiles. With this trajectory planner, we propose a robust
EMPC control, which ensures that the controller is able to meet these new power requirements.
The mathematical study of the new controller is performed to ensure stability and reachability
characteristics, and the results are presented in comparison with PD and pure EMPC.