Optimisation and comparison of different powertrain layouts for parallel hybrid electric vehicles equipped with continuous transmission

The development of an efficient hybrid electric vehicle (HEV) platform needs an optimal design of its powertrain layout. This study is concerned with parallel HEVs (PHEVs) equipped with continuous transmission. First, different types of continuous transmissions, including continuously variable transmission (CVT), power-split CVT (PS-CVT) and multi-fixed ratio PS-CVT (MF-CVT), are discussed and their simulation models are presented. Also, various combinations of these continuous transmissions with PHEV configurations (namely, pre-transmission and post-transmission configurations) are introduced. Then, for a given PHEV model, several powertrain layouts resulting from combining the considered continuous transmissions and PHEV configurations are optimised over a standard drive cycle. The optimised powertrain layouts are compared from different perspectives, for instance the vehicle fuel consumption, emissions and some dynamic performance measures. In particular, the sensitivity of the PHEV performance characteristics to the driving cycle pattern, when it is equipped with each optimised layout, is investigated.