Real-time Estimation and Compensation of Road Slip for Longitudinal Control

Abstract

SUMMARYOne important problem in tire modeling and its application to vehicle control is to quantitatively describe tire slip effect which is a dynamic interaction between the tire and road surface. Several tire slip models have been established, which can be divided as static models such as Bakker-Pacejka magic model and dynamic models such as LuGre model. It is generally recognized that the former provides a reasonably good curve-fitting from experimental data. However, the main difficulty in using those models is real-time estimation of the tire slip because it behaves as a random variable. It is impossible to estimate the tire slip exactly at each time instant. Even if this estimate is available, compensation for it in a controller is not easy. It is thus suggested that tire slip makes sense to longitudinal control only when it is considered statistically or on average. Based on this idea, a new definition of tire slip is proposed, which makes the real-time estimation and compensation practical. This method can also be applied to all-wheel-drive and/or all-wheel-brake vehicles without extra hardware installation. Two most important effects of tire slip on vehicle longitudinal motion, i.e. vehicle acceleration/deceleration capability and vehicle moving distance measurements, have been considered. Methods to compensate for the tire slip in longitudinal control have been proposed. Some experimental tests have been carried out.