Electric motor mounting system validation with subsystem and powered e-axle tests 2023-01-1097

As more and more electric vehicles (EVs) on dedicated platforms are being developed and launched, powertrain (PT) mounting systems evolve to focus on the specific requirements of the electric drive units (EDUs) – especially the partially opposing targets of controlling powertrain motion under torque and enhancing high frequency isolation. Vibracoustic has faced this challenge by adapting its motor mount system simulation methodology as well as by extending and enhancing its subsystem and e-axle test capabilities. In modern battery electric light vehicles, the electric drive unit (EDU) in the front or the rear axle is typically suspended on the vehicle body on three or four bushing. An isolated subframe may be added between the EDU and the vehicle body for improved NVH via double isolation. The initial layout of the EDU mounting system linear, such as the number, position and orientation of the motor mounts as well as their linear and non-linear stiffness properties, during the quotation phase as well as its continuous optimization after business nomination are the foundation for an optimal NVH performance. Vibracoustic uses multi-body simulation (MBS) for the basic modal tuning of the motor mounting and subframe mounting systems as well as the tuning of the mount force-deflection-curves under torque. Various sensitivity checks ensure the robustness of the optimal system layout regarding torque and production variation influences. To support early-stage model validation, Vibracoustic analyzes the modal properties of the EDU or the EDU / subframe assembly to ground. For more comprehensive investigations, Vibracoustic has devised unique axle test rigs to analyze and optimize the NVH of entire axles without the surrounding vehicle. Load cells at all interface points, acceleration sensors and other signal sources permit a comprehensive NVH characterization of an axle. Upgrading the axle test rig with a battery simulator, external liquid cooling and an automation system has enabled the NVH investigation of electric axles under their own power – an industry first. A recently added optical kinematic measurement system now allows the tracking of all 6 DOF motions of any axle and driveline component, e.g. under EDU torque or due to wheel excitations. Measurement results can be overlaid with the CAD model and used to correlate against multi-body system simulations. In this presentation, we will share a first correlation study of 6D optical kinematic measurements with multi-body simulations for both test approaches – the simplified experimental modal analysis and a full powered e-axle test on a chassis dyno. The modal analysis test results ensure an early validation of the linear multi-body system model, while the “e-axle under torque” tests support and verify the optimal tuning of the nonlinear force-deflection-curves of the EDU mounts. We will explain the system simulation and test setups, compare and assess the simulation and test results, and give an outlook of future applications.