Dual back-stepping observer to anticipate the rollover risk in under/over-steering situations. Application to ATVs in off-road context

In this paper, an ATV (All-Terrain Vehicle) rollover prevention system is proposed. Dynamic instability evaluation is based on the on-line estimation and prediction of the Lateral Load Transfer (LLT) from a vehicle model based on two 2D representations. As off-road vehicles are considered, grip conditions have a large influence. They are here estimated relying on observation theory. Nevertheless, two main behaviours (over/under-steering) may be encountered pending on grip and vehicle configuration. Since only a low cost perception system can be considered in ATV applications, these two opposite dynamics cannot be explicitly discriminated. As a result, two observers are designed, according to the vehicle behaviour, to estimate on-line the terrain properties (grip conditions, global sideslip angle and bank angle) and a “supervisor” selects on-line the right observer. Next, a predictive control algorithm, based on the extrapolation of rider´s action and the selected estimated dynamical state, allows the rollover risk to be anticipated, enabling to warn the pilot and to consider the implementation of active actions. Simulations and full-scale experimentations are presented to discuss the efficiency of the proposed solution.