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

Authors: M. Klomp; R. Thomson

Addresses: Saab Automobile, SE-461 80, Trollhättan, Sweden. ' Swedish National Road and Transport Research Institute, SE-402 78 Gothenburg, Sweden

Abstract: 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.

Keywords: vehicle dynamics; AWD vehicles; all-wheel drive; vehicle handling; vehicle performance; vehicle understeer; road holding; front drive force; rear drive force; force distribution; modelling; lateral grip limits; driveline configurations.

DOI: 10.1504/IJVD.2011.043272

International Journal of Vehicle Design, 2011 Vol.56 No.1/2/3/4, pp.34 - 48

Received: 16 Mar 2010
Accepted: 19 Nov 2010

Published online: 10 Apr 2015 *

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