Influence of front/rear drive force distribution on the lateral grip and understeer of all-wheel drive vehicles

Journal article, 2011

In this paper, the combined longitudinal and lateral road holding capability for All-Wheel Drive (AWD) vehicles with equal left/right longitudinal forces is analysed using a simple single-track model and assuming quasi-steady state conditions. To facilitate an improved correlation of the single-track model to more complex models, closed-form expressions that better describe critical axle performance parameters than currently used approximations are necessary. New expressions for the lateral grip limits and the vehicle understeer are therefore developed to account for general cases of front/rear drive force distributions. In order to visualise the effect of an arbitrary front/rear drive force distribution on the lateral grip, a contour plot, called the dynamic square, is used. The developed single-track model is applied to four particular driveline configurations (including an optimal front/rear distribution) and visualised in the dynamic square diagram, thereby demonstrating the application of these methods for analysis of modern driveline systems.