Root Cause Analysis and Structural Optimization of E-Drive Transmission 2020-01-1578

This paper describes the simulation tool chain serving to design and optimize the transmission of an electric axle drive from concept to final design with respect to NVH.

A two-stage transmission of an eAxle is designed from scratch by the initial layout of gears and shafts, including the optimization of gear micro geometry. After the shaft system and bearings are defined, the concept design of the transmission housing is evaluated with the help of a basic topology optimization regarding stiffness and certain eigenfrequencies. In the next step a fully flexible multi-body dynamic (MBD) and acoustic analysis of the transmission is performed using internally calculated excitations due to gear contact and bearing interaction with shaft and gear dynamics for the entire speed and load range. Critical operating conditions in terms of shaft dynamics, structure borne noise and noise radiation are evaluated and selected as target for optimization in the following steps.

Critical operating conditions are detected by a detailed root cause analysis (RCA) including operational modal analysis of assembled transmission, modal and panel contribution evaluation, operational deflection shape analysis (ODS), numerical transfer path analysis (NTPA) and transfer function (TF) evaluation. Based on the RCA result, the transmission housing design is exposed to the new optimization loop using different methods and tools and based on the dynamic loads. The design is optimized with the goal of reducing the emitted noise. The final housing design is verified by repeating the MBD and acoustic analysis. The developed simulation methodology and tools can successfully identify the main noise sources from the e-drive transmission. Followed by design optimization, the emitted noise is reduced, and the design can be improved.