Multi-Mode Trajectory Planning for Four-Wheel Independent Steering Vehicles Under Emergency Obstacle Avoidance Scenarios

Four-Wheel Independent Steering (4WIS) vehicles can independently control each wheel angle to achieve multiple steering modes, thereby expanding their motion space. However, existing trajectories do not match the multiple steering modes, making it difficult to leverage the stability of same-direction steering and the agility of opposite-direction steering of the front and rear wheels. This results in 4WIS vehicles facing challenges in generating trajectories that balance flexibility and stability under emergency obstacle avoidance scenarios. To address this, this manuscript proposes a multi-mode trajectory planning method for 4WIS vehicles under emergency obstacle avoidance scenarios. It decomposes the multiple steering modes of 4WIS vehicles into stable side-move motion and flexible yaw motion. By integrating these two motions, we establish a comprehensive kinematic model for 4WIS multi-mode operation. Based on this, the method combines side-move and yaw motions to construct a multi-mode risk field. The field is then iteratively optimized by the ILQR-MPC method to generate obstacle avoidance trajectories with sideslip and yaw angles, providing reference for the side-move and yaw motions across the multiple steering modes. Results show that the proposed method can generate trajectories that balance flexibility and stability, providing a foundation for safe and efficient obstacle avoidance.