Experimental verification of nonlinear sliding mode observer for accurate estimation of vehicle sideslip angle and lateral tire forces

This paper investigates the estimation of the sideslip angle and lateral tire-road forces for a class of nonlinear road vehicles. A Second-Order Sliding Mode Observer (SOSMO) is developed as an extended-state observer to simultaneously estimate lateral tire forces along with other measurable variables. The vehicle’s sideslip angle is then estimated independently using two distinct methods: dynamical equations and an inverse model-based estimation approach. The latter method introduces an innovative tire model that incorporates nonlinear tire-road friction characteristics, effectively simulating lateral force behavior. Comparative simulations and experimental analyses across two practical scenarios demonstrate that the proposed strategies, which do not require detailed tire-road interaction modeling, outperform conventional estimators such as the Extended Kalman Filter (EKF) and the State Dependent Riccati Equation Filter (SDREF). The experimental results particularly highlight the superior accuracy and efficiency of the developed SOSMO-based estimation strategies in providing estimates of the sideslip angle and lateral forces, offering reliable and cost-effective solutions compared to traditional methods.