Road Response Optimization

Abstract

Automobile design increasingly relies upon CAE (computer aided -engineering) technology to sim ulate vehicle performance. Simulation of NVH (Noise, Vibration and Harshness) provides d esigners and analysts with insights into their designs which not only advance produ ct competitiveness but also i m- prove pa ssenger comfort. An important area of NVH is assessing the response of the veh icle as it traverses a road that contains bumps. Power Spectral Density (PSD) methods can be used to characterize the r e- sponse of the vehi cle in the frequency domain due to input PSD information that characterizes the roug h- ness of the road by the energy present across a range of freque ncies. This paper discusses the addition of a design cap ability for this type of analysis within MSC.Nastra n. PSD and RMS responses have been added to those available in opt imization. Semi - analytical methods are utilized to compute the sens i- tivities of PSD and RMS responses for the optimiz a- tion in MSC.Nastran. An introduction to the techno l- ogy underlying r oad r esponse optimization is followed by a brief theoretical discussion and some comments on the implement ation of the capability in MSC.Nastran. Two exa mples are provided in this paper to illustrate the new capability. The first exa m- ple is a small ideal ized vehicle model which demo n- strates the potential of the new technique deve loped. The second example is a large full vehicle model. In this exa mple, engine mounts, modeled with springs, masses and dampers, are s elected as design variables. Different o bjectives are explored and di scussed.