Most of the prior studies on power-split hybrid electric vehicle's (PS-HEV) design focused on the powertrain configuration optimization. Yet, depicting the selected configuration is highly required for further design steps, ultimately manufacturing. This paper proposes an automatic approach to generate all the feasible kinematic diagrams for a given configuration with a single planetary gear (PG) set. While the powertrain configuration, which is the output of prior studies, illustrates the connection of the powertrain components to the PG, the kinematic diagram is a schematic diagram depicting the connections and arrangements of the components. First, positioning diagrams, specifying the position of the components with respect to each other and to the PG, are used to find all the possible arrangements. Then, given that the positioning diagrams have a one-to-one relationship with the kinematic diagrams, the feasible kinematic diagrams are identified using a set of feasibility rules applicable to the positioning diagrams. Finally, few guidelines are introduced to select good kinematic diagrams that best suit the overall vehicle design. Various configurations were investigated, and three of them including Prius and Voltec first-generation single PG configurations are discussed. The study reveals that the kinematic diagrams that have been patented are only a subset of all the feasible kinematic diagrams, and that even some good kinematic diagrams with better manufacturability are identified using this methodology. Thus, this methodology guarantees the search of the entire design space and the selection of kinematic diagrams that best suit the desired vehicle.
Optimal design of three-planetary-gear power-split hybrid powertrains