Powertrain Optimization and Performance Analysis of Series-Parallel Hybrid Transmissions With Clutches and Gears

Series-parallel hybrid systems have become an important development direction for hybrid vehicles. To improve the energy efficiency of series-parallel hybrid systems, in this study, first, the working mode of the series-parallel hybrid system with a clutch at the end of the engine is analyzed, and then, the impact of the clutch on the fuel economy and dynamics is investigated. Second, the rapid-dynamic programming (Rapid-DP) algorithm is used to conduct a comparative study with the current mainstream improved series-parallel scheme from the perspectives of fuel economy and acceleration, in which the multiobjective particle swarm optimization (MOPSO) algorithm is used to optimize the powertrain parameters, with energy consumption and acceleration performance as the design objectives. Based on a rigorous energy efficiency analysis, a new multimode series-parallel hybrid powertrain configuration (intelligent multi-mode drive (i-MMD)-Clutch-Gear Ratio[internal combustion engine (Ice)]) is proposed, in which the clutch and gear are added at the engine end. The proposed i-MMD-Clutch-Gear Ratio(Ice) configuration is also simulated in a real cycle, and the proposed configuration performs better than the conventional series-parallel hybrid powertrain, with a 6.01% improvement in fuel savings and a 20.76% improvement in acceleration performance.