To enhance energy efficiency of series-parallel hybrid system, this paper
investigates and compares the effects of adding the gear ratio at different
power source position on the performance of the vehicle. Firstly, the effect of
adding gears at various positions is analyzed on the basis of intelligent
multi-mode drive (IMMD) configuration, and the potential working modes resulting
from the added gear ratios at different power source positions are examined.
Secondly, multi-objective particle swarm optimization (MOPSO) algorithm is used
to optimize the transmission ratio of new gears, laying the groundwork for
comparing different configurations. Moreover, the fuel economy performance of
the optimized series-parallel configuration was evaluated using a rapid dynamic
programming approach with the objective function of minimizing fuel consumption
during power transfer. Finally, in accordance with the aforementioned research,
the acceleration performance and economic performance of different
configurations were compared quantitatively. The comparative analysis shows that
for series-parallel hybrid powertrain, increasing the driving motor direct drive
gear had a significant effect on improving the dynamic performance, the 100 km
acceleration time increased by 14.08%. increasing engine direct drive gear had a
significant effect on improving the economy under urban dynamometer driving
schedule (UDDS), the fuel consumption was reduced by 4.76% on average,
increasing the engine and driving motor direct drive gears at the same time had
a significant effect on improving the economy and dynamics, exhibiting a 20.63%
improvement in acceleration and a 4.29% improvement in fuel economy under
worldwide harmonized light vehicles test cycle (WLTC) cycle.