This paper presents the design and validation of a novel multi-mode transmission (MMT) for a hybrid electric vehicle (HEV) using a single electric machine (EM), which implies compact and low cost. The topology of the MMT planetary gearset is the same as that of conventional four speed automatic transmissions. The MMT uses two planetary gearsets and four clutches to combine an engine and an EM with the vehicle, and the EM is operated as a motor or a generator. The MMT realizes five power flow modes, which are developed into sixteen operating modes, including one motor-only mode, four engine-only modes, four compound driving modes, six braking modes, and one charging while parking mode. The single EM HEV solution avoids losses from another EM and extra power electronics which are employed in many existing HEVs. 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. The fuel consumption of the proposed hybrid vehicle system is compared with a benchmark vehicle which uses a planetary gearset, two EMs and no clutch. Simulation results under New European Driving Cycle show that the fuel consumption of the proposed HEV is comparable to the benchmark vehicle. Reasons for comparable results are explored, which indicates the fuel economy potential of the new concept.
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