Energy-saving potential of global optimal strategy for series-parallel hybrid transmissions based on driving cycle generalization

Energy efficiency and driving cycle adaptability are the key factors in testing the energy management strategy (EMS) performance of hybrid transmissions. However, rule-based (RB) EMSs have yet to fully exploit the energy-saving potential of hybrid transmissions, and the energy utilization performance is often obtained for only a single standard driving cycle. To elucidate the energy-saving potential of RB EMS for hybrid transmissions, vehicle driving data were first collected, and performance was analyzed in low-, medium-, and high-speed domains. A traffic scene-based driving cycle generalization method was then proposed. Furthermore, typical driving cycles were constructed based on speed domain distribution and mileage ratio to provide driving cycle support for EMS accelerated simulation testing. Based on these conditions, the difference in fuel consumption performance between the charge depleting-charge sustaining (CD-CS) and dynamic planning (DP) strategies was compared. The results showed that compared to CD-CS, the energy-saving ratio of DP ranged from 3.80–33.93 % under different driving cycles. Finally, the difference in fuel consumption performance between the two strategies was verified through real vehicle testing, which provided a direction for the optimization of RB EMSs, along with key driving cycles to be considered for EMS energy-efficiency verification.