Optimization of bushing stiffness for vehicle vibration reduction using dynamic substructuring approach

In the field of vehicle NVH (Noise, Vibration, Harshness), extensive research has aimed to minimize the transmission of vibrations and noise from various excitation sources to passengers. A primary excitation source is the powertrain, which consists of the engine in internal combustion vehicles and the motor in EVs. The noise and vibration generated by these sources are transmitted to the cabin through the vehicle structure, particularly at low frequencies. As the powertrain-induced noise and vibration propagate to passengers through the bushings, optimizing their stiffness is crucial for effective noise and vibration reduction. This study proposes an optimization method for bushing stiffness based on FRF (Frequency Response Function) Based Substructuring (FBS), one of the widely used Dynamic Substructuring techniques. A simplified vehicle model is divided into active and passive parts, and the coupling stiffness between them is identified using FBS theory. The system's dynamic characteristics are then updated by modifying the bushing stiffness. An optimization approach was implemented, setting receiver vibration, calculated based on the force transmitted to the passive side, along with source vibration, as objective functions. This study was validated using a simplified FEA rather than full-scale vehicle testing, allowing for cost-effective and time-efficient analysis under various stiffness conditions.