Multispeed transmissions are helpful for improvement of the economy and drivability of electric vehicles (EVs). In this paper, we propose a two-speed transmission based on dual planetary gear mechanism, in which shifts are realized by torque transfer between two brakes located on ring gears. To synthesize the dynamic and economic performances of the vehicle, a multiobjective optimization problem is constructed for gear ratio optimization and Pareto-optimal solutions of gear ratio combinations are obtained by Nondominated sorting genetic algorithm-II (NSGA-II). In particular, the minimum electric energy consumption of the EV is calculated with a fast Dynamic Programming (DP) in each iteration. Following this, a constant-output-torque control (COTC) scheme is adopted for the torque phase and inertia phase of gearshift process to ensure constant output torque on the wheel. To enhance transient responses, the feedforward–feedback controller structure is applied and a disturbance observer is integrated to improve robustness. Simulation results demonstrate that the two-speed transmission has much better performance in terms of acceleration time and energy economy compared to the fixed-ratio transmission, and the proposed gearshift control method is able to achieve fast and smooth gear shift robustly while maintaining constant output torque.

This paper presents a gear shift method for the dual clutch transmission (DCT) with integrated electric motor in pure electric drive mode. In contrast to clutch-to-clutch shift in conventional DCT, a good gear shifting process relies on the coordinated control of the motor and synchronizer in electric drive mode of the hybrid DCT. To shorten the torque interruption time and reduce the wear of the synchronizer during engagement, the key point is to adjust the oncoming gear speed to the output shaft speed rapidly. This study provides a speed regulation control framework based on model predictive control (MPC) and disturbance observer (DO), where the MPC controller is designed to achieve a good tracking performance and the DO is to eliminate effects from exogenous disturbances. Simulation and experimental results demonstrate that the proposed approach can attain a rapid and robust gear shifting performance.

Precise motor speed regulation control is essential to achieve a good gear shifting quality of the integrated motor-transmission (IMT) system, in which the relative speed between outgoing shaft and the gearwheel to be engaged can be eliminated directly through regulation of the motor speed. The speed regulation control confronts the difficulty that there exist external disturbances on the motor shaft, like the unknown load torque arised from bearing friction, oil shearing and oil churning, etc. To deal with these disturbances, a robust speed regulation controller combined a nominal proportional control and integral sliding mode control is proposed. The former is designed to achieve a good speed tracking performance and the latter provides functionality of disturbances rejection. The effects of different controller parameters for the robust controller design are assessed via simulations. Moreover, to verify the effectiveness of the combined control scheme in practical engineering use, experiments are carried out on a test bench with a real IMT powertrain system. Results indicate that the proposed approach can attain a rapid and smooth speed regulation process with a simple controller structure and good robustness.