New online estimation algorithm of lateral tire-road coefficients based on Inertial Navigation System

For the sake of simplicity, control laws for autonomous vehicle mainly use linear tire models, but this modeling is only valid for small slip angles. Hence, to keep this hypothesis valid, tire's behavior has to lie within the limits of handling, i.e. there is a threshold the slip angle cannot surpass. This paper develops a new estimator for the cornering stiffness and maximum lateral friction coefficients. These parameters provide important information on the ground conditions and are beneficial for improving the stability of the vehicle. The algorithm is based on estimated lateral tire forces and on a 3 zones adaptive algorithm, including a Dugoff theoretical tire model. It will allow to set up a model not only for the linear part but for the whole range of slip angles, providing the trend of the tire behavior at each time and informing about the future evolution of lateral forces. The advantage of the algorithm is that no measurement of lateral tire forces is needed and few parameters are required such as yaw rate, longitudinal and lateral velocities obtained through an effective Inertial Navigation System, wheel rotational speeds and steering angles. Simulations conducted on realistic dynamical situation validate the algorithm efficiency.