The automotive industry is experiencing a profound change due to increasing pressure from environmental and energy concerns. This leads many automakers to accelerate hybrid and electric vehicle development. Generally hybrid and electric vehicles create less noise due to their compact engines (or no engine). However, customer satisfaction could be negatively impacted by the peak whine emitted by electric motor. Unlike conventional gas vehicles, the strategy for reducing motor whine is still largely unexplored.
This paper presents an analytical study on electric motor whine radiated from the transmission in a hybrid vehicle. The analysis includes two stages. Firstly, a detailed finite element (FE) model of the transmission is constructed, and case surface velocities are calculated utilizing motor electromagnetic force. Then a boundary element model is built for evaluating noise radiated from the transmission surface using acoustic transfer vector (ATV) method. The normal modes and frequencies of the motor stator are compared with those obtained from test results to gauge the accuracy of FE model.
The correlated model is applied to evaluate the acoustic response of hybrid transmission including the effect of motor torque, radial and tangential force, and radiating hot spots. Sensitivity studies are also conducted for propose noise reduction countermeasures.