The Study of Torque Control Characteristics for the Optimization of the NVH of an Electric Vehicle

Over recent years IDIADA has developed several prototype electric vehicles as well as testing a number of electric powertrain configurations. Generally the electric motor output shaft delivers the torque to the transmission under a considerable level of high-frequency load variation and with noticeable torque irregularities that must be smoothed out in order to fulfill general NVH targets. This paper deals with the development phase of a prototype vehicle in which a specific testing activity was carried out to improve the overall NVH behavior of the powertrain. For this purpose, the mechanism of energy transference from the current to the motor and from the motor to the downstream driveline components was deeply characterized. The activity was aimed at smoothing the abrupt change in torque delivery and limiting the transfer of torque irregularities from the motor to the transmission. The torque control software calibration and the driveline elements were developed in order to reduce the noise and vibration critical frequency ranges. New methodologies and testing approaches focused on electric powertrain allowed an accurate analysis in frequency and time domain for the detection of the causes of the NVH issues and helped to properly optimize the torque delivery. The study finally enabled the definition of the powertrain specifications with particular attention to the electric motor torque control and the transmission elements for the entire vehicle speed range.