Design and screening of double-planetary-gears multimode hybrid powertrain based on molecular topology graph

Dual planetary-row hybrid systems are widely used in production models of major automotive brands for their superior power and fuel economy. However, only a limited number of configurations have been commercialized, leaving a vast design space unexplored. This paper proposes a four-stage methodology for designing and screening dual planetary-row multimode hybrid powertrain configurations, based on a chemical molecular topology model. First, molecular modeling of the powertrain is performed. Secondly, the topological indexes is introduced for isomorphism detection of the planetary rows, and the assignment rules of the power sources to the nodes of the planetary rows are defined. Then, clutches are assigned to realize a specific base model. Finally, the dynamics and fuel economy of the new configuration are simulated. The process incorporates appropriate constraints and screening conditions to eliminate invalid designs efficiently. Simulation results demonstrate that the proposed powertrain achieves smooth mode switching, along with excellent fuel economy and dynamic performance.