On the Influence of Anti-Roll Stiffness on Vehicle Stability and Proposal of an Innovative Semi-Active Magnetorheological Fluid Anti-Roll Bar

Modern vehicles are equipped with several active and passive devices whose function is to increase active safety. This paper is focused on the anti-roll stiffness influence on vehicle handling, and follows a theoretical approach. The work firstly develops a quadricycle theoretical model, useful to study the influence of anti-roll stiffness on the vehicle local stability. The model, involving non-linear phenomena, is simplified by proper linearizations. This procedure allows local stability analysis with low computational load. At the same time, the linearized model takes into account the dynamic effects induced by load transfers through a tyre-road interaction model sensitive to the vertical load. The study is conducted considering the anti-roll stiffnesses of the two axles as parameters. The proposed model defines the relationship between the anti-roll bars stiffness and the system state. In order to realize an adaptive system able to provide a variable roll stiffness, a semi-active anti-roll bar prototype, employing magnetorheological fluid, is described. Such device gives the possibility to quickly change the roll stiffness, according to the system state, to preserve its stability.