Multi-Modal Emergency Obstacle Avoidance Planning and Tracking Control for Four-Wheel Steering Vehicles

To enhance active safety in four-wheel steering (4WS) vehicles during emergency obstacle avoidance, a planning and tracking control method incorporating multi-modal motion features was proposed. A motion primitive library was constructed by integrating the kinematic characteristics of both oblique moving and conventional 4WS modes. An improved Hybrid A* algorithm was employed to perform multi-modal composite search within the state space. A multi-objective cost function was used to generate the optimal avoidance path. A model predictive tracking controller was designed based on a vehicle dynamics model. Smooth modal transitions were ensured via constrained optimization. Co-simulations with CarSim and Matlab/Simulink showed that, the proposed multi-modal method reduces required avoidance space and time, suppresses sideslip angle, and improves both the safety and stability of the vehicle under varying road adhesion conditions.