Geometric Identification of an Elastokinematic Model in a Car Suspension

Abstract

This paper deals with the modelling of a car suspension including rubber bushings. Significant differences are found between data from the numerical elastokinematic model and experimental results. One reason for these differences comes from geometrical shifts of bushing centres in the real suspension with respect to the numerical model. The aim of the present work is to reduce the differences by identifying the geometric parameters of the elastokinematic model. To achieve this goal, a method is proposed for computing the location and orientation of each part and joint in the assembled suspension. The first stage of the method uses measurements on separate parts to define joint location in the coordinate system local to the part. In the second stage, measurements are performed on the assembled suspension mechanism using a portable coordinate measuring machine for locating parts and joints in a global coordinate system. Based on these data and elastic joint stiffnesses, bushing deflection is computed at the static equilibrium of the vehicle and used to identify the real joint locations on parts. This identification method is tested on a pseudo-McPherson suspension and improves model behaviour during vertical wheel movement.