ABSTRACT 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). INTRODUCTION PHEV PERFORMANCE CHARACTERISTICS AND CHALLENGES The first electrical continuous variable transmission (e-CVT) introduced with the strong-hybrid electric vehicle consists of two major components: a planetary gear and an electric machine. It was initially used as a replacement of aconventional multi-gear transmission to improve fuel efficiency and reduce emissions of the internal combustion engine (ICE). With design improvement, an e-CVT is also used in a PHEV application with increased electrical propulsion ability. Such a PHEV oriented e-CVT design will effectively enable the vehicle's energy diversity using both petroleum and electric energies, without much compromised vehicle functionality and affordability. The challenges for the PHEV and HEV powertrain design using an e-CVT also arise due to its multi-disciplinary nature and system complexity. To facilitate the design of an e-CVT hybrid system for a PHEV, this study applies a simulation and optimization based approach to identify and compare the peak powertrain performance of different operating modes on four hybrid powertrains. The two primary performance characteristics under comparisons are peak torque capability and electric only drivability. The new modeling program provides more flexibility in modeling and optimizing newer powertrain architecture designs, comparing with the established powertrain modeling tool, PSAT. Peak torque capability of a vehicle directly determines its acceleration and towing ability. Determining the peak torque capability of an existing vehicle, however, is not always straightforward. In a conventional vehicle (CV) with a discrete-ratios transmission, determination of the peak transmission output can be performed, by multiplying ICE output torque with gear ratios. In an e-CVT based powertrain configuration, however, there are multiple power actuators which creates numerous propulsive combinations. To produce a new design and associated control algorithm which fully utilize the powertrain's capability, substantial amount of developing time is needed even for an experienced engineers. The developed controller, however, is not necessarily capable of fully utilizing the best performance potential of the powertrain. The second performance characteristic under Performance Study and Comparison of Representative e-CVT Based Hybrid Powertrains2011-01-1442 Published 04/12/2011 Leon Zhou and Zoumin Dong University Of Victoria Copyright © 2011 SAE International doi:10.4271/2011-01-1442Downloaded from SAE International by Univ of California Berkeley, Friday, July 27, 2018investigation, the electric only drivability, will significantly affect the electric energy usage a