Efficient Design Space Exploration of Multi-Mode, Two-Planetary-Gear, Power-Split Hybrid Electric Powertrains via Virtual Levers

The recent industry trend of incorporating multiple planetary gears (PG) and clutches in power-split hybrid electric vehicles has enhanced their potential fuel economy and acceleration performance. However, this increase in performance potential comes at the cost of increased design and control complexity. In this paper, we propose a highly efficient design methodology that finds the optimal multi-mode, two-PG powertrain by extending our recently developed virtual lever, a modeling tool that eliminates the redundancy in the physical design space and hence minimizes the computational load associated with optimizing over
multiple
different types of PGs. First, every operating mode of every powertrain architecture is modeled using the virtual lever, whose parameters comprise the virtual design space. Second, the fuel economy and acceleration time are evaluated for every design in this continuous, virtual design space. Then, the powertrain architectures are compared by their respective Pareto frontiers in the fuel economy — acceleration time plane. Furthermore, a design space conversion method is used to group the evaluated designs by their respective feasible physical realizations to compare the 16 possible physical realizations of the generic Volt 2nd, which is found to be the best powertrain architecture. The proposed method uncovered several different physical realizations of the generic Volt 2nd that outperforms General Motors’ existing Chevy Volt 2nd powertrain.