Optimization and coordinated control of gear shift and mode transition for a dual-motor electric vehicle

Abstract

The electric vehicle equipped with dual motors and four-speed automated manual transmission has demonstrated its superiority in improving energy efficiency and dynamic performance. To exploit this configuration effectively, optimal shift schedules and corresponding mode selection maps are proposed separately for accelerating and braking conditions. Hysteresis zones between upshift and downshift lines are created by properly integrating a priority factor into the equivalent motor efficiency. Interestingly, the proposed shift schedules depend not only on the motor efficiency map, motor torque allocation, but also on the current working gear pair. Besides, the intersections of the shift schedules and mode selection borders show that gear shift and mode transition need to be implemented at the same time. Therefore, a coordinated control strategy is developed to handle these requirements. Finally, simulation results show that the case of without hysteresis zones achieves minimum electricity consumption but with many undesired and unnecessary gear changes. Conversely, with comparable energy economy, the introduced priority factor of 0.02 avoids the shift hunting effectively. Moreover, taking the advantages of the powertrain configuration, the proposed coordinated control strategy eliminates all torque gaps under the gearshift and mode transition, so great shift quality is achieved.