Optimization of a Dual-Motor Coupled Powertrain Energy Management Strategy for a Battery Electric Bus Based on Dynamic Programming Method

As the global environment and energy problems are becoming increasingly serious, electric vehicles are expected to play an important role in current and future transportation. In this paper, the configuration of a coaxial series dual-motor coupled propulsion system is analyzed, and the optimization objective function is obtained for a power management strategy in which the control strategy is extracted based on a dynamic programming (DP) method. The simulation model of the powertrain is tested in MATLAB with different strategies under various driving cycles. The control strategies extracted from DP show that the DP/single-mode strategy (strategy based on DP under single-mode) reduces the energy cost by 8.0% and the DP/dual-mode strategy reduces it by 8.8% compared with the traditional proportional control strategy which simply distributes torques of the two electric motors according to default ratios. In addition, the DP/dual-mode strategy performs similarly well under the urban dynamometer driving schedule and UKBUS6 with reductions of 9.1% and 8.6%, respectively. Vehicle experiments are also performed with the YuTong ZK6120BEV under Chinese typical urban bus driving cycles. As a result, the DP/dual-mode control strategy reduces the energy consumption of the 6120BEV by 2.85% on average compared with the traditional proportional control strategy.