Estimation of Contact Forces of a Four-Wheel Steering Electric Vehicle by Differential Sliding Mode Observer

This paper deals with the estimation of tire/road contact forces. These forces play a big role on the dynamics of vehicles. Basing on longitudinal, lateral, yaw and wheel dynamics of an electric vehicle ('known as Robucar'), the contact forces can be estimated through second order differential sliding mode observer. A step by step algorithm allows estimating velocities and accelerations and then these forces can be deduced. The results are compared with the empirical model of these forces given by Michelin.