Experimental Validation Of Tire-road Friction Observer Based On Self-aligning Torque∗

Automated and cooperative driving is one of the most promising but challenging tasks of automotive industry. For guaranteeing safe operation of automated driving, observing vehicle and environment states is of necessity, in which the tire-road friction coefficient (μmax) is a crucial parameter. We give a solution to this problem by using the estimation framework proposed by the authors [1] for estimating the μmax by utilizing total aligning torque information and experimentally validate this observer. Firstly, we briefly introduce the proposed nonlinear adaptive observer. Then, a robust activation criteria is applied for reliable estimation. The estimation results from the proposed observer and Extended Kalman Filter (EKF) are subsequently compared under various μmax with experiments. The results show that 1) stability can be guaranteed with the proposed observer in various maneuvers while the EKF cannot. 2) The observer performs similar in terms of root mean square estimation error compared to EKF (when EKF is stable). Finally, detailed discussions are conducted to describe the potential limitations of the proposed method for μmax estimation.