A methodolgy for evaluating the structure-borne road noise prior to a prototype vehicle using direct force measured on a suspension rig

Abstract

Numerous previous studies have been conducted on quantifying road noise through transfer path analysis (TPA) using the matrix inversion and the dynamic stiffness methods. However, the matrix inversion method is a calculation that always contains error, even when treated with the best condition number found by trial and error iteration to match the calculation SPL (sound pressure level) to measured SPL. Furthermore, the caveat of the dynamic stiffness method is that it requires accurate dynamic stiffness value up to the frequency range of interest, which, in reality, is rarely available and is challenging to obtain. Therefore, TPA using these two methods is only possible when a complete vehicle is available. For the sake of cost and time reduction, circumventing these limitations is crucial within the vehicle production period. The main focus of the present study is to directly obtain the operational forces at the suspension mounting points neglecting the effect of the vehicle body through a special suspension rig. The suspension rig is verified through a comparative analysis with the actual baseline vehicle measurement up to 250 Hz. In addition, an example approach for finding suspension's NVH performance improving factor using the rig benchmarking technique is introduced.

Derivation of road noise improvement factor within a suspension system using the inverse substructuring method

“…The FBS model for improving the vibro-acoustic performance of the suspension was also derived and applied in the verification process. For the validation test, road excitation was substituted with shaker excitation in the vertical direction, using a previously developed suspension rig, 1 which enables direct measurement of the body input force at the coupling points. A specially developed cross member jig was used for the validation test.…”

“…The active side is where the external force is entering, and the passive side is the body side to which the operational force is transmitted (see Figure 1(a)). If the conditions of the force equilibrium and displacement compatibility are satisfied, the equal but opposite reaction force to both the active and the passive sides, R, can be used to obtain the following relation (see equations (1) and 2)x B = H B R ð1Þ…”

“…Hence, various approaches have recently been attempted to improve the experimental inefficiency in terms of the vehicle NVH and to shorten the duration of the vehicle development process. In one of these studies, Song et al 1 deployed a new methodology for road noise performance evaluation using the suspension rig. This rig enables the separate tackling of these influencing factors by identifying the vibro-acoustic performance of a sole suspension, neglecting the body coupling effect.…”

Accuracy improvement method for dynamic substructuring models in vehicle systems

“…Despite many studies on model improvement, practical limitations remain when applying the DS technique in automotive fields. Van der Seijs et al (2017) performed a practical physical study using the substructuring technique, and Kang (2019a, 2019b) and Song et al (2016) proposed a test jig to develop a vehicle suspension system by applying a DS technique while acknowledging the limitations of practical testing. Kim et al (2020) estimated system characteristics using virtual parameters and suggested practical uses for the DS method.…”

Estimation of body input force transmission change due to parts’ modification using the impedance method under rolling excitation

“…One of the most ubiquitously performed strategies for improving structure-borne road noise is optimizing the dynamic properties of the bushing at a dominant acoustic energy transfer path, as two-thirds of the road noise is conquered by suspension of the body input operational forces. 2,3 To closely attend to the problem of improving the operational force, Song et al 4 developed a suspension rig for practically obtaining the direct force at hard points, neglecting the vehicle’s body and hence solely assessing the suspension’s vibro-acoustic performance. A basic schematic representation of the developed suspension rig is shown in Figure 1.…”