The automotive industry continues to develop new powertrain and vehicle technologies aimed at reducing overall vehicle-level fuel consumption. Specifically, the use of electrified propulsion systems, including electrified and electric drive units (EDU), is expected to play a significant role in helping OEMs meet fleet CO2 reduction targets for 2025 and beyond. The change to vehicles propelled by electrified powertrains leads to a reduction in vehicle noise levels. Despite the overall noise levels being low, the NVH behavior of such vehicles can be objectionable due to the presence of tonal noise coming from electric machines and geartrain components. In order to ensure customer acceptance of electrically propelled vehicles, it is imperative that these NVH challenges are understood and solved.
Specifically, this paper discusses the EDU NVH development process. This includes considerations for CAE/test-based development and validation processes to ensure optimal NVH development. The CAE-based processes will include examples based on the use of advanced multi-body systems analyses coupled with finite element methods, addressing both electromagnetic as well as geartrain-related forcing functions.
Further, the development of a novel electric drive sound level (EDSL) approach to test-based characterization of EDUs will be presented. Noise shares from the geartrain, broadband mechanical noise, primary electromagnetic forcing, and switching are extracted through novel transfer function calculations. The overall approach gives any EDU development team the ability to compare noise shares against scatterbands, conduct root cause analysis on specific noise issues, and predict sound levels at untested loads. Results from case studies are utilized to highlight the details of the developed methodology. Finally, aspects of EDU integration into the vehicle to assure refined vehicle-level NVH behavior will be discussed.