A New Experimental Methodology to Estimate Chassis Force Transmissibility and Applications to Road NVH Improvement

The performance of structure-borne road NVH can be cascaded down to three major systems: 1) vehicle body structure, 2) chassis/suspension, 3) tire/wheel. The forces at the body attachment points are controlled by the isolation efficiency of the chassis/suspension system and the excitation at the spindle/knuckle due to the tire/road interaction. The chassis force transmissibility is a metric to quantify the isolation efficiency. This paper presents a new experimental methodology to estimate the chassis force transmissibility from a fully assembled vehicle. For the calculation of the transmissibility, the spindle force/moment estimation and the conventional Noise Path Analysis (NPA) methodologies are utilized. A merit of the methodology provides not only spindle force to body force transmissibility but also spindle moment to body force transmissibility. Hence it enables us to understand the effectiveness of the spindle moments on the body forces. The feasibility and applicability of the methodology was experimentally demonstrated. The accuracy of the methodology was verified. This methodology can be used for the benchmarking and system cascading for target setting to achieve a desired road NVH performance as well as for diagnosing root causes in the problem solving procedure. Two different vehicles were used for the demonstration of the root cause analysis implementing the method. The comparison of the chassis force transmissibility of these two vehicles is presented to show the merits of this methodology.