This presentation was made at the NAFEMS Americas "Creating the Next Generation Vehicle" held on the 14th of November in Troy.

The automotive engineering community is now confronting the largest technology transformation since its inception. This includes the electrification of powertrains for more efficient consumption and cleaner emissions, the reinvention of the battery with fast wireless charging capabilities and finally the advent of a fully autonomous vehicle. Compounding to these technology changes, the automotive companies design verification process is moving away from a major reliance on physical testing to almost a full virtual simulation product verification process.

The automotive engineering community is now confronting the largest technology transformation since its inception. This includes the electrification of powertrains for more efficient consumption and cleaner emissions, the reinvention of the battery with fast wireless charging capabilities and finally the advent of a fully autonomous vehicle. Compounding to these technology changes, the automotive companies design verification process is moving away from a major reliance on physical testing to almost a full virtual simulation product verification process.

Resource Abstract

Fast-growing vehicle electrification makes the performance of electric drive draw more and more attention. NVH issue caused by electromagnetic excitation and torque ripple is one of the key attributes directly affecting drivers’ impression. Accurate NVH simulation for the electric drives requires high fidelity mechanical analysis model. Specially, the installation of electric motors often involves contact interference in the process of press fit. Therefore, an effective analysis method is desired to address the severe nonlinear effects presented in this process in the support bracket vibration and housing radiated noise analysis for motor whine and other associated NVH performance assessment.



Linear dynamics (often modes-based frequency domain analysis) alone provides fast and expedient solutions for many NVH problems; however, there are cases where the nonlinearity plays such a significant role in NVH performance evaluation that they should not be neglected. An effective and feasible analysis modeling method to simulate interference fit and other nonlinear features possibly involved in both the installation and operating process was developed for E-motor NVH analysis and assessment. First, the method was confirmed in a correlation study on FRF Response of the E-motor Assembly in an Electric Rear Axle Drive (eRAD) of a hybrid electric vehicle. Additionally, the method was also successfully employed to a surrogate full assembly of the Primary Drive Unit (PDU) of a pure electric vehicle with full and light contact interference. Related parametric study was performed on the effect of interference magnitude, and interference pattern and distribution on NVH responses.



The analysis procedure developed in this study includes 3 steps. Step 1 simulates the press fit and other related preloading effects using nonlinear static analysis, in which contact was defined with interference between the housing inner face and the stator outer face. In Step 2, normal modes extraction is conducted as a preparation for next step. The final step (step 3) is a steady state dynamic perturbation procedure, calculating the frequency response for either structural vibration or acoustic pressure due to mechanical or electromagnetic forces. The comparison with test result was preformed and reasonably good correlation was achieved. The method can be readily utilized to account for other linear and nonlinear effects in the system for NVH prediction such as preloading, assembling, plasticity, thermal loading etc.