Cécile Mattrand

Estimation of road profile variability from measured vehicle responses

ABSTRACT When assessing the statistical variability of fatigue loads acting throughout the life of a vehicle, the question of the variability of road roughness naturally arises, as both quantities are strongly related. For car manufacturers, gathering information on the environment in which vehicles evolve is a long and costly but necessary process to adapt their products to durability requirements. In the present paper, a data processing algorithm is proposed in order to estimate the road profiles covered by a given vehicle, from the dynamic responses measured on this vehicle. The algorithm based on Kalman filtering theory aims at solving a so-called inverse problem, in a stochastic framework. It is validated using experimental data obtained from simulations and real measurements. The proposed method is subsequently applied to extract valuable statistical information on road roughness from an existing load characterisation campaign carried out by Renault within one of its markets.

ON THE CONSIDERATION OF UNCERTAINTY IN DESIGN: OPTIMIZATION – RELIABILITY – ROBUSTNESS

Structural designs aspire to ensure the functionality of a system respecting specific requirements defined by engineers. Structural optimization techniques are widely used to optimize the system performances while garanteeing that specific requirements are fulfilled. However, it is worth remembering that uncertainties might affect all design quantities which can make the design problem much more arduous to solve. This paper aims to discuss the formulation of design problems under uncertainty. Several strategies might be identified when considering uncertainties in the objective and/or constraint functions. Moreover, this paper aspires to clarify the notions of robustness and reliability. After a presentation of each formulation, an academic example illustrates the different strategies and shows the main differences between results of each one. Thus, the choice of the formulation should be viewed as a crucial step of design procedure. N. Lelièvre, P. Beaurepaire, C. Mattrand, N. Gayton and A. Otsmane