A Theoretical and Experimental Investigation of NVH of In-Wheel Reduced Motor System

To enhance the power density of the system and reduce production costs, the in-wheel reduced motor system (IWRMS), characterized by its integrated design and control, is poised to become the future development trend. However, the high speeds of motors and gear reducers can lead to challenges such as system stability and issues related to NVH (Noise, Vibration, and Harshness). This paper specifically addresses the NVH concerns associated with the IWRMS. Firstly, a bench test scheme was established, and vibration and noise tests were conducted under a range of conventional operating conditions. The results indicated that at the torque of 200 Nm and the speed of 5500 rpm, the noise sound pressure level reached 86.2 dB, highlighting significant vibration and noise issues within the system. Subsequently, operating deflection shapes (ODS) testing and analysis were performed on the IWRMS. Vibration responses of 48th order show that breathing mode of the motor housing bring resonance phenomenon, which differs from the mode of torsional resonance of the housing in conventional electric drive systems. The electromagnetic forces for each order were reconstructed at the inner diameter node of the stator and incorporated into the finite element model of the structure for vibration and noise simulation. This approach enabled a quantitative analysis of the contribution of each electromagnetic force and facilitated targeted optimization of these forces. Finally, to counteract the 48th order vibration of the motor, harmonic optimization was achieved through methods such as rotor slotting. This strategy reduces the radial force at its source and offers valuable insights for optimizing the NVH performance of the IWRMS.