Abstract: The four-wheel independent multi-mode steering system integrates four-wheel steering and in-wheel motor differential steering functions, enabling multiple steering modes such as front-wheel, four-wheel, and compound steering. Under varying speeds and road adhesion conditions, the critical stability boundaries associated with each steering mode differ significantly and evolve dynamically. To address this, a hierarchical multi-mode switching stability control method is proposed. The upper layer formulates a quantitative description of stability boundaries under different steering modes, defining the stable domains and switching criteria across various driving conditions. The lower layer models the system as a switched system composed of multiple subsystems and employs a common Lyapunov function to design the switching control strategy, ensuring globally asymptotic stability during mode transitions. The proposed method is validated through co-simulation using Carsim and MATLAB/Simulink. Results demonstrate that the approach effectively suppresses vehicle sideslip angle and yaw rate fluctuations under high-speed and low-adhesion conditions, thereby enhancing vehicle stability in extreme driving scenarios.

Key words: four-wheel independent steering system, mode switching, critical stability boundary, common Lyapunov function