Integrated optimal design of configuration and parameter of multimode hybrid powertrain system with two planetary gears

The performance of power-split hybrid powertrain systems vary with its configuration due to the differences of the number of planetary gear (PG) set as well as the type, number and installation location of shift actuators (clutch or brake). The 2-PG scheme has some advantages over 1-PG and n-PG (n >=3) systems in terms of structure, performance, and control complexity of the system. The competitive advantages of 2-PG scheme depend on configuration design (analysis, evaluation and screening) and parameter optimization. In this article, systematic methods of configuration design, analysis, evaluation, and screening for 2-PG multimode power-split hybrid powertrain systems are proposed and all potential configurations of 2-PG, connection positions of power components, different number of actuators, and combinations of different operating modes have been taken into consideration. A stepwise optimization design method (DOE sampling with self-adaptive PSO algorithm) is also formulated to optimize the 2-PG system's characteristics parameters (the two ratios of ring gear to sun gear) and the ratio of main reducer. Finally, an efficient automatic development process and tool based on engineering constraints is designed to optimize the 2-PG system scheme and to achieve the excellent system performance.