Precursors of Instability for a Vehicle Traveling in Curve

Nowadays, the automotive field takes care of human safety in the everyday driving. In this sense, the vehicle dynamics control systems and ADAS (Advanced Driver Assistance System) play a crucial role for both active and passive safety. In terms of handling, the critical issues for the everyday driver are during braking or steering maneuvers: the main idea of this paper is to investigate the possibility to recognize some critical behaviors leading to vehicle instability, using only the wheel sensors signals, already available as mandatory in actual passenger car (in particular for ABS). In order to do this, a seven degrees of freedom model of a vehicle that runs in a curve with constant longitudinal speed is formulated. With no particular reference to the power unit (IC motor or electrical motors), three different traction schemes configurations are considered. The numerical solutions of the model are analyzed to evaluate their stability, the associated modal shapes and the modal participation factors. A systematic analysis allows recognizing some vehicle behaviors that may constitute instability precursors useful to develop a suitable control logic. Results provided by both a standard vehicle dynamics simulation software and a "on-road" test are presented and discussed to verify the actual feasibility of the proposed precursors employment.