Vehicle Lateral Stability Control Based on Shiftable Stability Regions and Dynamic Margins

Vehicle lateral stability control is one of the most critical aspects of vehicle safety control. In this paper, aiming at keeping the vehicle states (lateral velocity and yaw rate) always in the vehicle stability regions, a novel lateral stability control method, which consists of shiftable region-based stability analyses and a corresponding stability controller, is proposed. In the stability analyses, two features of the stability regions are introduced. First, a shifting vector is formulated to explicitly describe the shifting feature of lateral stability regions, so that the shiftable regions are not necessarily re-estimated with respect to a varying steering angle input. Second, dynamic margins of the stability regions are formulated and applied to avoid the penetration of vehicle state trajectory with respect to the stability region boundaries. With these two features, the shiftable stability regions are feasible for an accurate stability analysis, where a projection method is adopted to determine the relative location/distance between the vehicle state point and the closest boundary of the stability region. Based on the analyses, a dynamic sliding mode controller, where the sliding surfaces are selected as the stability region boundaries with the proposed dynamic margins, is designed to keep the vehicle states always in the shiftable stability region. To validate the effectiveness of the proposed control design and analyses, two maneuvers through the co-simulation between Matlab/Simulink and CarSim, namely a high-speed constant cornering and a double lane change maneuvers, are presented and discussed.