This work focused on examining and demonstrating the potential of a plug-in fuel cell hybrid vehicle as an alternative for sustainable local personal transportation in urban environments. Specifically, a vehicle simulator was developed with experimentally validated component models. Using this simulation environment, a heuristic trade-off study was performed by extensive simulations while varying 3 design parameters: maximum fuel cell power, battery pack capacity and final drive ratio. Based on this trade-off study, a vehicle prototype was built consisting of a 2kW fuel cell and a large battery pack (6.1 kWhr). This configuration allowed the vehicle to operate both charge-sustaining hybrid and charge-depleting hybrid modes and to have a substantial range in charge-depleting mode while meeting the required overall performance envelop.
Using the same simulation tool, a simple PI controller with battery SOC feedback was developed as a supervisory energy management controller for the vehicle. The same controller structure allowed to operate in both charge-sustaining and charge-depleting hybrid mode. The controller gains were numerically optimized to minimize the fuel consumption while minimizing other performance metrics. The results of this heuristic controller tuning were compared to an optimal dynamic programming solution indicating that the PI controller with optimized gains is only mildly sub-optimum.
This optimized controller was implemented through rapid prototyping onto the vehicle prototype micro-controller. Validation data sets were collected with the vehicle in mixed urban environments indicating that the prototype vehicle performed as intended, despite differences between the actual implementation and the simulated configurations. Many recommendations were made ranging from the type of vehicle platform used, to the technology deployed in the prototype design and realization, to the vehicle supervisory control methodology to improve the prototype in future studies.
In summary, the study was a success and served an excellent template to build upon in future studies. It also clearly demonstrated that a fuel cell PHEV vehicle potentially offers very significant advantages in terms of energy use and petroleum use while significantly mitigating global warming and pollution in urban or commuting environments, hence offering a significant potential toward a more sustainable personal automotive transportation future.