A NONLINEAR VEHICLE BICYCLE MODEL FOR SUSPENSION AND HANDLING CONTROL STUDIES A. Zin ¤ O. Sename ¤ M. Basset ¤¤ L. Dugard ¤ G. Gissinger ¤¤ ¤ Laboratoire d’Automatique de Grenoble, UMR CNRS-INPG-UJF 5528, ENSIEG-BP 46, 38402 Saint Martin d’H`eres Cedex, FRANCE. Email: fAlessandro.Zin, Olivier.Sename, Luc.Dugardg@inpg.fr ¤¤ Laboratoire Mod´elisation, Intelligence, Processus, Syst`emes, ESSAIM, 12 rue des fr`eres Lumi`ere, 68093 Mulhouse Cedex, FRANCE Email : fm.basset, g.gissingerg@uha.fr Abstract: This paper presents a mathematical ”3D” nonlinear (NL) bicycle model (for passenger cars) dedicated to chassis control design (suspension, braking and steering subsystems . . . ). The proposed model takes into account the vertical, longitudinal and lateral motions (in a coupled way), and rotational wheel dynamics, while neglecting the roll motion. In order to validate this model, simulation results were obtained and compared to experimental measurements, for some representative driving trials. As illustration, linear control- oriented models are obtained by linearizing the previous nonlinear model. Then two optimal control strategies are developed to improve ride confort, road holding (thanks to active suspensions) and vehicle handling (thanks to active steering). Simulation results of the control strategies applied to the NL model are then given. c °IFAC Copyright 2004. Keywords: Vehicle model, ride confort, road holding, vehicle handling, LQ control. 1. INTRODUCTION The vehicle is a complex system having a strongly nonlinear behavior in limit handling, (Wade-Allen et al., 2002). It is composed of several subsystems like engine, driveline, suspensions, wheels, tires. . . . The study of the ”whole” vehicle needs to integrate different subsystem models, (Rauh, 2003). For subsystems and vehicle design, these models are more or less complex. However these ones are generally not usable for control system design. Indeed at this stage, control-oriented models can often be simple (e.g. linear). At the prototype testing level, the required models may be very detailed and complex (many parameters, not always easily available, are required) to get realistic simulations. Thus they may include physical equations as well as behavioral models, which make them difficult to be reused (Connair et al., 1999; Syers et al., 2002). In this paper a mathematical model is developed, to be used between development and prototype testing levels. Its operation requires only few parameters to be known. The model is modular in order to allow for easy integration with other subsystems. Furthermore, concerning vehicle dynamics (which cover a wide range of subject material, (Crolla, 1996)), the model is valid for the study of ride confort, road holding and vehicle handling in classical operations (e.g. braking in straight line, small cornering. . . ). These topics are linked (Cooke et al., 1997) but are generally studied separately in automotive literature, (Ackermann, 1996; Esmailzadeh and Taghirad, 1997; Gaspar et al., 1996; Mammar and Koenig, 2002). In the case of handling, a classical model used in the automotive literature is the single-track model, composed by only two .....