Instantaneous Center of Rotation Tracking Control of Four-Wheel Independent Steering Vehicles Under Large-Curvature Turning Conditions

Compared with other steering systems, Four-Wheel Independent Steering (4WIS) can control not only yaw motion but also their unique side-move motion to provide intelligent vehicles with stronger trajectory tracking capabilities. However, existing 4WIS wheel angle control often aims at zeroing the sideslip angle of the Center of Gravity (CoG), which inhibits the unique side-move motion of 4WIS vehicles. Especially under large-curvature turning conditions, relying only on yaw motion, the system is prone to entering a state of nonlinear instability; its trajectory tracking accuracy and stability are difficult to guarantee. In response, this paper proposes a 4WIS vehicle instantaneous center of rotation (ICR) tracking control method under large-curvature turning conditions. It converts traditional wheel angle control into ICR control. Through the coordinated control of side-move and yaw motion, trajectory tracking accuracy and stability are ensured under large-curvature turning conditions. The proposed ICR tracking control includes two parts: ICR control and trajectory decomposition. ICR control constructs a polar coordinate system with the vehicle CoG as the pole and establishes a decoupled mapping of side-move and yaw motion to the ICR. By predicting and optimizing the deviation between the ICR and its reference, the side-move and yaw motions are coordinated to achieve effective tracking of large curvature trajectories. Trajectory decomposition mainly converts the trajectory tracking target into the ICR control reference. By combining the particle model and trajectory curvature, polar coordinates are used to decompose the trajectory curvature into side-move and yaw curvatures, and through rolling optimization of lateral and heading errors, the target trajectory is decomposed into side-move and yaw control reference. HIL experimental results show that the proposed ICR tracking control strategy can effectively improve the trajectory tracking performance of 4WIS vehicles under large-curvature turning conditions.