Pontryagin's Minimum Principle-based power management of a dual-motor-driven electric bus

To further improve the operating efficiency of a dual-motor-driven electric bus, a simple and robust power-management strategy was proposed. This study is comprised of three parts. (i) A systematic modeling approach for the efficiency of a dual-motor propulsion system (DMPS), which contains a wet clutch, transmission gears, bearings and two driving motors, has been proposed and verified experimentally. The correlation coefficient between the experimental data and the model simulation data is approximately 0.9, which indicates the validity and reliability of the DMPS model. (ii) Pontryagin's Minimum Principle (PMP) was applied to optimize the control strategy under three different types of driving cycles. Based on the analysis of the PMP control strategy, a two-parameter-based mode switching control was proposed for determining the optimal working mode of the DMPS. Then, a broken line-based power split control was developed, and the turning point was determined according to the optimization results. (iii) By combining the mode switching control strategy and the power split control strategy, a new control strategy was formulated, and its robustness was verified through six driving cycles. The simulation results show that the new control strategy can significantly improve the DMPS efficiency performance in different types of driving cycles compared with the original control strategy.