  The powertrains of today's hybrid electric vehicles (HEVs) are developed for
human drivers and, therefore, may not be the optimum choice for future
Autonomous vehicles (AVs), given that AVs can accurately manipulate their
velocity profile to avoid unnecessary energy loss. In this work, we closely
examine the necessary degree of hybridization for AVs compared to human drivers
by deploying real-world urban driving profiles and generating equivalent AV
drive cycles in a mixed autonomy scenario. We solve the optimal energy
management problem for HEVs with various motor sizes from the automotive
market, and demonstrate that while human drivers typically require a motor size
of around 30 kW to fully benefit from hybridization, AVs can achieve similar
gains with only a 12 kW motor. This greater benefit from a smaller motor size
can be attributed to a more optimal torque request, allowing for higher gains
from regenerative braking and a more efficient engine operation. Furthermore,
We investigate the benefits of velocity smoothing for both traditional cars and
HEVs and explore the role of different mechanisms contributing to fuel
consumption reduction. Our analysis reveals that velocity smoothing provides
greater benefits to HEVs equipped with small motors compared to non-hybrid
vehicles and HEVs with larger motors.
