Cascaded Predictive Control of Tire Force Saturation Levels for Vehicle Stability

This paper proposes and demonstrates a cascaded predictive control strategy that quantifies and uses longitudinal and lateral tire force saturation for directional stability control of road vehicles. Saturation is explicitly defined and computed as the deficiency of a tire to generate a linearly increasing force in either the lateral or longitudinal direction. The optimal management of lateral saturation levels is set as the objective for an upper level controller, while the optimal management of longitudinal saturation among all tires is set as the objective for a lower level driving/braking torque distribution controller. This cascaded predictive scheme exploits prevailing time scale separations between the lateral vehicle dynamics and the tire/wheel dynamics. The performance of the approach is illustrated using simulations of a medium-duty truck undergoing a transient handling maneuver.