Electric Drive Unit CAE Modeling for NVH Vibroacoustic Performance Prediction

The present thesis addresses the vibroacoustic performance prediction of an electric drive unit developed by Garrett for battery electric vehicle applications. This is a relatively young and developing topic in the engineering literature, with limited research available. The high competitiveness of the BEV market renders the powertrain’s vibroacoustic performance a distinctive advantage among carmakers and OEMs, often protected by intellectual property. Most analyses are based on testing and empirical measurements rather than on a rigorous theoretical procedure. The methodology employed to build a complete simulation, from evaluating the electromagnetic loads of the electric motor to predicting the radiated noise, is extensively discussed in Chapter 3. This methodology represents a novel integrated approach, encompassing and linking multiple physical domains: electromagnetic, mechanical, and acoustic. Multi-body dynamics plays a central role in the methodology, serving as the interface between these physical domains and representing the mechanical transmission of the electric powertrain. Here, analogies between the dynamics of the components constituting the multi-body system and the equations implemented by the simulation software are presented. Chapter 1 provides an introduction to NVH phenomena in electric powertrains and discusses their human-perception-based nature. Chapter 2 offers a deeper analysis of the electric drive unit’s components and identifies their common sources of vibration and noise. The simulation is conducted using GT-SUITE™ software, which combines numerical and multi-physical capabilities. Chapter 4 describes the test specimen, test rig, and the model setup in relation to its dynamic behavior. The simulation primarily focuses on the vibratory behavior of the powertrain caused by gear meshing, leaving the acoustic domain for future developments. Due to the lack of data regarding the electric machine’s electromagnetic model, boundary torque and speed conditions were simplified, and the excitation of the electric motor casing was not considered. Order tracking analysis is employed to post-process and analyze the displacements measured by the accelerometers, at the aim of isolating the gear mesh vibration orders. A detailed description of the order tracking method, providing insight into the root causes of the transmission and rotating machine dynamics, along with the analysis of results, is presented in Chapter 5.