Topology optimization for hybrid electric vehicles with automated transmissions

Currently, many different topologies are designed with different transmission technologies such as automated manual transmission (AMT) and continuously variable transmission (CVT). The choice of topology determines the energy-flow efficiency between the hybrid system, the engine, and the vehicle wheels. The optimal topology minimizing fuel consumption is influenced by the transmission technology. Therefore, an AMT (high efficiency) and a push-belt CVT (moderate efficiency), are used in this research for comparison. In addition, a controlled switching topology is introduced as a benchmark, where controlled coupling with additional clutches of the electric machine before or after the transmission minimizing transmission losses and improving hybrid performance is investigated. The results showed that a switching topology can significantly improve CO2 emission reduction (average relative improvements between 2% and 7%), particularly for CVT-based hybrid vehicles. Moreover, in case of an AMT, a precoupled topology is preferable, and in the case of a CVT, a postcoupled is preferable for full-hybrid vehicles. For these cases, selecting the optimal fixed topology can improve the relative CO2 emission reduction between 2% and 8%.