Robust NVH Development of Steering Systems Using In-Situ Blocked Forces from Measurements with Low-Noise Driver Simulators

The in-situ measurement of blocked forces has become an important method to develop products of superior NVH quality for the automotive industry. Due to the invariant property of the blocked force this method allows characterization of structure-borne sound sources in arbitrary installations (e.g. source on supplier test bench) and employing the obtained intrinsic source data to predict vibration in, or sound radiated from, different receiver structures (e.g. source installed in vehicle). The latter application is known as Virtual Acoustic Prototyping and represents an interesting engineering tool to conduct subjective and objective design evaluations remote from the vehicle. Using the example of a column type electric power steering system (CEPS), this paper proposes a robust approach towards designing low-noise steering systems using in-situ blocked forces. In-situ Transfer Path Analysis (iTPA) is conducted in the vehicle to verify that the CEPS is a structure-borne sound source. The vehicle transfer functions are then combined with blocked forces measured in-situ on standard test benches to model the sound pressure response of the CEPS virtually operated in the vehicle. The obtained virtual acoustic prototype is validated employing low-noise driver simulators to perform dynamic steering on the bench and in the vehicle under highly repeatable conditions.