Bin Wu, Chan-Chiao Lin, Zoran Filipi, Huei Peng and Dennis Assanis
The University of Michigan

This paper investigates development of power management strategies tailored specifically to a medium truck with parallel hydraulic hybrid powertrain. The hydraulic hybrid vehicle (HHV) system is modeled in MATLAB/SIMULINK environment. As the starting point, this study considers rule-based power management strategy adopted from the previous HEV study. Dynamic Programming (DP) algorithm is used to find the optimal trajectories for gear shifting and engine/motor power splitting, assuming that the federal urban driving schedule represents typical use of a delivery truck. Implementable rules are derived from analyzing the optimal trajectories, and it is shown that the changes are to a large extent driven by high power density and low energy density of the hydraulic propulsion system. System behavior demonstrates effectiveness of new strategies in further improving the fuel economy of the hydraulic hybrid truck.