Reducing Noise in an Electric Vehicle Powertrain by Means of Numerical Simulation

The noise performance of fully electric vehicles is essential to ensure that they gain market acceptance. This can be a challenge for several reasons. Firstly, there is no masking from the internal combustion engine. Next, there is pressure to move to cost-efficient motor designs such as Switched Reluctance Motors, which have worse vibro-acoustic behaviour than their Permanent Magnet counterparts. Finally, power-dense, higher speed motors run closer fundamental frequency to the structural resonances of the system [1]. Experience has shown that this challenge is frequently not met. Reputable suppliers have designed and developed their "quiet" sub-systems to state of the art levels, only to discover that the assembled E-powertrain is unacceptably noisy. The paper describes the process and arising results for the noise simulation of the complete powertrain. The dynamic properties are efficiently modelled as a complete system and subjected to motor excitation (torque ripple, electro-magnetic forces and rotor imbalance). Innovation in this project comes from the speed of the modelling and analysis, so that analysis and data interpretation comes early enough in a project to be effective in reducing the noise problems. This contrasts with the approach of simulating problems that have already occurred in testing. Actions to reduce the motor noise are explained and identified. System dynamic response identifies the operating points in which different excitation mechanisms are most problematic and steps are taken to reduce the dynamic response. Also, problematic conditions can be identified where innovative motor control algorithms are necessary.