Impact of Mounting Blocks on Drivability

Precedent papers have shown that motor-block (i.e., electric motor and speed reducer) rolling motion onto its mounting blocks has an important effect on the drivability rating. The drivability aspect is crucial for an electric vehicle because of the high torque gradient at low speeds or between regenerative and motor modes. Within the context of the new European emission standard, automotive engineers have to focus their research on fuel-efficient vehicles. Therefore, many car manufacturers are directed toward zero-emission vehicles as a solution, hence the development of the electric vehicle. To lead this vehicle project from the very early design steps, it is very important to assess and optimize customer perception during vehicle use. We also need to assess the difference between the vehicle response to driver request and that expected from the driver himself. This aspect of vehicle customer perception is called drivability and is evaluated by numerous maneuvers such as tip-in and back out of the accelerator pedal (tip-out) or acceleration from a rest position (takeoff). During tip-in, the torque gradient causes oscillations of the driveline and a jerk of the vehicle. Moreover, precedent works have shown that torque excitation causes a roll motion of the motor block (i.e., the electric motor and speed reducer) onto its mounting blocks and therefore shocks on the vehicle acceleration.