Estimation of road friction for enhanced active safety systems: Algebraic approach

Knowledge of tire friction force capacity, i.e. tire-load frictional coefficient, is important for the control of vehicle active safety systems. In this paper we review several methods for friction estimation and develop two robust and cost effective methods based on a nonlinear least square approach and the peak aligning torque. The methods proposed in this paper utilize simple vehicle lateral dynamics, steering system, and front tire dynamics. The first estimator uses direct calculation based on front tire self-aligning torque and the second method is based on a nonlinear least square method. These estimators are verified with Carsim under various conditions.