This paper shows a modular NVH engineering process based on Dynamic Substructuring and component TPA techniques, using experimental data obtained on a fully electric BMW i4 vehicle. Following the component TPA approach, the electric drive unit (EDU) of the BMW i4 is considered as the vibration source and is described by equivalent forces on the EDU. To describe the presence of a second vibration source, originating from the wheels running on the drums, a set of equivalent forces at the rear wheel hubs is included. The quality of the equivalent forces is evaluated using criteria as defined in a recent ISO standard on the topic [1].
Transfer paths from the EDU up to the targets in the cabin, i.e. sound pressure at the driver’s ear and vibrations at the seat rail, are obtained through Dynamic Substructuring of the individual subsystem models using the Lagrange Multiplier Frequency Based Substructuring (LM-FBS) method. The subsystem models include multiple sets of rubber bushings, a rear axle carrier and the vehicle trimmed body. Transfer paths from the rear wheel hubs up to the targets in the vehicle are obtained from FRF measurements. The individual subsystem models are obtained through measurements using the Virtual Point Transformation in DIRAC, a software application specifically designed to generate subsystem models from FRF measurements using 3- or 6-DoF Virtual Points. The rubber bushings are modeled using the inverse-substructuring approach, which is also available in DIRAC. A second application, COUPLE, is then used to generate NVH predictions based on the modular subsystem models and the equivalent force descriptions.