Cooperative Brake Control Strategy for Electric Vehicle Equipped With a Two-Speed Uninterrupted Mechanical Transmission

Regenerative braking of EV (electric vehicle) can enhance fuel efficiency to a great extent in urban areas. In addition, transmission plays a great role on the vehicle fuel economy and comfort and there are some research focus on the multi-speed transmission on EV. However, only limited number of scholars discussed about the influence of multi-speed transmission system on regenerative braking system. This paper focus on the effects of Electric Vehicle equipped with a Two-speed Uninterrupted Mechanical Transmission., which consist of a set of planetary gear, band brake and friction clutch. The transmission is capable of achieving seamless downshift which indicates that it can still transfer torque while downshifting. At the same time, as traction interruption of shift exerted an influence on the comfort during brake, this article put forward with a cooperative control algorithm considering the real response of electrohydraulic braking system in order to compensate the traction interruption and established an dynamic simulation model to testify the algorithm. The transmission dynamic model is developed by utilizing Euler-Lagrange equations to derive the motion while the other models are some simplified models. The whole model is applied by using the SimDriveline library of the MATLAB/Simulink. The simulation results of EV which commit a downshift while brake and the EV keep the gear are compared at the last demonstrate that the downshift strategy can save more energy without excessive oscillations.