Design and Analysis of a Novel Multimode Transmission for a HEV Using a Single Electric Machine

This paper presents the mathematical modeling and analysis of a novel multimode transmission (MMT) for a hybrid electric vehicle (HEV) using a single electric machine (EM), which implies compactness and low cost. The single-EM solution avoids losses from another EM and its power electronics, which are employed in many existing HEVs. The topology of the MMT planetary gearset is the same as that of conventional four-speed automatic transmissions (ATs). The MMT realizes five power flow modes, which are developed into 16 operation modes, including one Motor_only mode, four Engine_only modes, four Compound driving modes, six Braking modes, and one Charging while parking mode. The properly arranged clutches transmit power flow more flexibly, allow direct mechanical power transmission from the engine to the drive shaft, and avoid spin loss for the engine and energy conversion loss for the electric components. Simulation under the New European Driving Cycle (NEDC) shows that the fuel consumption of the proposed HEV is comparable to a benchmark “THS II-like” vehicle, which uses a planetary gearset, two EMs, and no clutch, which indicates the fuel economy potential of this concept.