Performance Study and Comparison of Representative e-CVT Based Hybrid Powertrains

An electronic continuously variable transmission (e-CVT) with integrated electric machines and planetary gears is widely used in the powertrains of hybrid electric vehicles (HEV). The e-CVT supports various promising hybrid powertrain designs, blending electric and mechanical drives with high efficiency and flexible energy sources. Identifying the peak performance characteristic of an e-CVT design for a given HEV, however, is a challenging task due to the complexity of hybrid propulsion system and the multi-disciplinary nature of hybrid powertrain design. In this work, model-based design and optimization methods are used to identify the peak synergetic performance of hybrid powertrains with an e-CVT. Four popular HEVs platforms have been studied: the Chevy 2-mode, Chevy Volt, Lexus RX450h, and Toyota Prius. The powertrains of these HEVs are modeled as nonlinear functions of several control variables, and their peak performances in both normal mode and electric-only mode are identified using simulation and a two-stage hybrid optimization method. To verify the results of the modeling and optimization from this work, comparisons are made with the results from the widely used Powertrain System Analysis Toolkit (PSAT), developed at the U.S. Argonne National Lab (ANL).