Design and Optimization of a P4 mHEV Powertrain 2022-01-0669

The EcoCAR Mobility Challenge (EMC) is the latest edition of the Advanced Vehicle Technology Competition (AVTC) series sponsored by the US Department of Energy. This competition challenges 11 North American universities to redesign a stock 2019 Chevrolet Blazer into an energy-efficient, SAE level 2-autonomous mild hybrid electric vehicle (mHEV) for use in the Mobility as a Service (MaaS) market.

The Mississippi State University (MSU) team designed a P4 electric powertrain with an 85kW (113.99 HP) permanent magnet synchronous machine (PMSM) powered by a custom 5.4 kWh lithium-ion energy storage system. To maximize energy efficiency, Model Based Design concepts were leveraged to optimize the overall gear ratio for the P4 system. To accommodate this optimized ratio in the stock vehicle, a custom offset gearbox was designed that links the PMSM to the rear drive module. This gearbox is a three-gear train with a ratio of 3.143:1, comprised of helical gears with integrated shafts within a custom two-piece aluminum case. Moreover, the rear drive module was modified to ease the integration process of the designed gear in the vehicle in compliance with competition rules. Overall, the designed P4 system contributes to a 34% improvement in fuel economy over the stock vehicle on the EMC combined drive cycle.