Dynamic tire forces in vehicles with semi-active suspensions

Assessment of vehicle tire forces is important in problems related to the structural health monitoring of highway bridges, damage to road pavements, design of suspensions, and road safety issues. In this paper, the effects of using semi-active control strategies, such as MR dampers, in vehicle suspensions on the dynamic tire forces are examined for the development of smart suspension systems for pavement- and bridge-friendly vehicles. The vehicle dynamics is described by a general linear MDOF model with multiple contacts (i.e., a multiple-axle vehicle) with the road. It is assumed that the tires are always in contact with the road surface. In particular, we are interested in the evaluation of the tire forces due to a harmonic excitation. A technique is developed to analytically assess the magnitude of the resulting tire force in the case of a passive suspension. Although the technique discussed cannot directly be applied to the calculation of tire forces in vehicles with controlled suspensions, it can efficiently be used for design purposes, which is demonstrated by an example of a semi-active suspension based on the sky-hook control. The discussion is amply illustrated by numerical examples.