Design and analysis of a coupling mechanism with dual planetary gear sets for the power split HEV

Hybrid electric vehicles (HEVs) are now used more and more widely, especially the power split HEVs. However, the fuel consumption of HEVs varies with the configuration of the power coupling device. In this paper, a novel power coupling mechanism with dual planetary gear sets is proposed, which is developed from an automotive transmission in the conventional vehicle. By analysing its power split characteristics, it is proved that two brakes are essential to be added into the power coupling mechanism. The addition of brakes enriches operation modes, which is effective to improve the system efficiency, though it would increase the complexity of the system. Characteristic parameters of the planetary gear sets are optimised. For accurate evaluations of the proposed configuration, a global optimisation control strategy is established based on the dynamic programming (DP) algorithm. Simulation results under different driving cycles show that the fuel consumption of HEV with the proposed power coupling mechanism is 6.89% and 8.30% lower than that of a benchmark vehicle. The proposed power coupling mechanism proves to be beneficial to improve HEV fuel economy.