Analytical Methodology to Derive a Rule-Based Energy Management System Enabling Fuel-Optimal Operation for a P24-Hybrid

The variety of different hybrid vehicles developed by car manufacturers has steadily increased in the last couple of years. One predominant hybrid configuration has been the parallel hybrid in P2-configuration. Due to the demand for further electrification to reach future fuel efficiency targets and improve pure electric driving performance, concepts of hybrid vehicles with at least two electrical machines come into focus. Herein, the concept of adding an individual electrical axle to a P2-hybrid is gaining interest. However, the system complexity of a so called P24-hybird increases significantly because the number of possible system states rises. This leads to an increased development and calibration effort for an energy management. Especially the transfer from an optimized operating strategy to a rule-based energy management is challenging. Thus a development framework for the calibration of an online energy management system (EMS) is needed. Within this paper the applicability of a methodology to derive a fuel-optimal EMS for P2-hybrids to P24-hybrids is investigated. The paper shows successfully, that the same fundamentals for P2-hybrids can be applied to P24-hybrids. This enables the determination of fuel-optimal maps for load point shifting and optimal e-drive thresholds for the switch from electric drive to hybrid mode. With that, a simple, yet fuel-optimal, rule-based EMS can be implemented. Since the used methodology proves to be independent from the hybrid topology a universal development framework to develop and calibrate a rule-based EMS can be established. Additionally, the differences and benefits within the fuel-optimal operating strategy of P24-hybrids compared to P2- and series hybrids is investigated. It is shown, that a P24-configuration yields the highest fuel-economy and overall system efficiency of the three hybrid configurations.