A Novel Approach to Real Time Tire-Road Grip and Slip Monitoring

It is a very challenging task to measure longitudinal slip of a tire on road surface in normal driving conditions, because of the very small value of the slip (a few 1/1000). This paper presents an industrially deployable method for Tire-Road Friction (TRF) monitoring applied to passenger vehicle. This method estimates the longitudinal wheel slip κ and the normalized friction coefficient μ, for low grip requirement driving conditions, in real time. It uses wheels velocity and forces applied on wheels bearings. Due to the imperfections in the wheel speed sensors used, signal to noise ratio from speed measurement is very low. A correction, taking into account the measured deterministic component of the speed measurement noise (called sensor signature), allows for a correction of wheels speed signals and, accordingly, a better estimation of slip. The obtained results demonstrate the ability of our method to distinguish between wet and dry roads during a longitudinal stabilized drive. This method finds applications in Adaptive Cruise Control systems, Driving Assistance systems and Intelligent Highways.