Research on instantaneous optimal control of the hybrid electric vehicle with planetary gear sets

Abstract

Power-split hybrid electric vehicle (HEV), mainly adopting the planetary power coupling mechanism, is superior in improving the fuel economy because the engine speed and torque are decoupled from those of the wheels. Focusing on a power-split HEV with dual-planetary gear sets, this paper establishes an instantaneous optimal control to regulate its power flow. Firstly, simulation-oriented models are established, including the coupling mechanism, the engine, the electrical machines and the battery. Secondly, feasible operation modes of the vehicle are analyzed. Also, the torque and speed equations between the engine and motors are obtained. On the basis of the above, the instantaneous optimization strategy, adaptive equivalent fuel consumption minimization strategy (A-ECMS), is designed, which is developed from the equivalent fuel consumption minimization strategy. The optimization strategy is of high robustness to different driving cycles. To realize the engine speed tracking, a PI controller is introduced. At last, the control effects of A-ECMS are compared with the effects of the engine optimal operating line control strategy. The effectiveness and rationality of two strategies are tested in the dSPACE real-time simulator. Test results under different driving scenarios prove that the A-ECMS is of better performance in ensuring the HEV fuel economy and the battery charging sustainability.