Slip slope change detection based on active drive force excitation

Abstract

Identification of the available friction potential is crucial for road safety but difficult, in particular at normal driving. This paper aims to contribute by presenting an effect-based method for slip slope change detection related to friction potential changes at all wheel-drive vehicles applying active drive force excitation. The proposed estimation approach relies above all on the wheel speeds and the axle/wheel drive forces of the front and rear axle. Different types of periodic active drive force excitation that are superimposed to the drive force requested by the driver while maintaining the desired level of speed or acceleration are investigated w.r.t. the availability of the estimates and overall effectiveness of the estimator. Vehicle tests are performed to evaluate theoretical results and the (co-)driver’s perception of the active drive force excitation. Results from both the simulation study and vehicle tests show that the proposed method allows to reliably estimate slip slope changes at all-wheel drive vehicles in driving conditions with low levels of drive force excitation.