Planetary gearsets (PGs) are key components widely used in automotive industry to realize power split electronic-continuously variable transmission (e-CVT) hybrid electric vehicles (HEVs) with high energy efficiency as well as satisfactory driving performance. However, a large number of combinations for one or more PGs coupled with several power sources and demanded switching mechanisms make researchers and engineers take time-consuming effort to choose an appropriate one for further development. In this paper, a design methodology in view of the operating characteristics of electric circulation is proposed to sort out all combinations of compound split e-CVT configurations specifically with two single-pinion PGs. Favorable configurations are selected mainly concerning with the existence of power recirculation and characteristics of electric circulation in favor of energy efficiency. Furthermore, a design case is carried out about the performance and fuel economy for a favorable powertrain using simulations under both software and real-time hardware-in-the-loop environments to verify the feasibility of the proposed optimization strategy based on electric circulation. Consequently, the proposed design methodology and classification offer an effective and systematic search, rather than a randomly exhaustive search, for compound split e-CVT hybrid systems, and, furthermore, can be applied to a large-scale design frame including multiple PGs and various powertrain types to achieve a computation-efficient search for the qualified multi-mode power split e-CVT HEVs.
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