REAL TIME TYRE-ROAD FRICTION COEFFICIENT IDENTIFICATION AND VEHICLE STATE ESTIMATIONS BY MEANS OF TYRE FORCE MEASUREMENTS

Aim of the present paper is to investigate how smart tyres can improve sideslip angle and friction coefficient estimation and to evaluate robustness of estimation to road bank angle. Smart tyres (SM) are an emerging technology aimed at turning the tyre into a sensor able to provide information about tyre-road contact. Among the different types present in the technical literature, a smart tyre constituted of two three-axial MEMS accelerometers directly glued on the inner liner is considered in this study. The adopted sensor in fact presents the advantages of tiny dimensions, low weight, minimal impact on the production process, wide bandwidth, high reliability and the robustness required to withstand the impulses occurring when the sensors enter and exit the footprint. Available measurements, which are provided once per wheel turn by the adopted smart tyre, are assumed to be longitudinal, lateral and vertical contact forces. To evaluate the effect of these additional measurements on sideslip angle and friction coefficient estimation, an Extended Kalman Filter (EKF) based on a single-track vehicle model was implemented. A five degree-offreedom (5 dofs) model accounting for the lateral, yaw, pitch, and roll motions of the vehicle was used on the purpose. Specifically, several handling maneuvers on variable adherence surface were simulated. Robustness of the observer to road bank angle and tyre parameters variation is also discussed.