Improved Wheel Speed and Slip Determination Considering Influences of Wheel-Suspension Dynamics and Tire Dynamics

The wheel speed and the slip are important signals for many modern automotive control systems. The performance of these systems strongly depends on the quality of the evaluated wheel speed and the slip. However, during car motion, especially during acceleration or braking, deflections of the flexibly mounted wheel suspension and of the tire disturb the measurement or rather the determination of these signals. In this paper an approach to increase the quality of the evaluated wheel-speed signal and the slip signal by considering these influences is introduced. The method considers the longitudinal motion of the wheel center, the tangential motion or rather the oscillations of the belt, the changing of the dynamic tire radius and the disturbances due to the angular motion of the wheel-speed sensor. To obtain the required kinematic values for the compensation, a mathematical model of the wheel suspension and of the tire is developed. The reconstructed signals are verified by means of measurement data taken during test drives with a BMW 318i. By comparing the slip as well as a μ-slip curve with and without the introduced compensation, the potential of the developed method is shown.