Hierarchical Coordinated Path-Following Control of Four-Wheel Steer-by-Wire Vehicles with Corner Module Actuation

Four-wheel steer-by-wire vehicles enable independent steering actuation at each corner, providing greater control flexibility for coordinated vehicle motion and path following. However, finite actuator dynamics and local steering loads can affect the wheel angles actually delivered to the vehicle, thereby influencing the overall steering response. To address this issue, this paper proposes a three-layer hierarchical steering control strategy for coordinated vehicle motion and accurate corner-level execution in four-wheel steer-by-wire vehicles. First, model predictive control (MPC) generates coordinated front- and rear-axle steering commands using weights calibrated offline by particle swarm optimization (PSO) and bounded state-dependent corrections from a fuzzy neural network (FNN) to the preview curvature and yaw rate references. Second, instantaneous-center-of-rotation (ICR) geometry converts the axle commands into four-wheel reference angles, accounting for differences between the turning radii of the left and right wheels and maintaining geometric consistency. Finally, active disturbance rejection control (ADRC) improves the execution performance of four independent permanent-magnet synchronous motor (PMSM) steering modules driven by field-oriented control (FOC), enabling wheel reference tracking and compensation for local steering-load disturbances. Simulations under representative driving conditions show that the mean lateral root-mean-square (RMS) error under ideal steering execution is 0.0278 m, 55.4% lower than that of the two-wheel-steering baseline. Regarding the finite corner actuator dynamics and the associated execution controllers, the worst-case lateral RMS error is 0.0631 m, still 27.9% lower than the same baseline, while the peak vehicle sideslip angle remains below 2.30°, with the applicability of the proposed framework at higher speeds and the capability limitations of the steering execution system also analyzed and discussed. These results show that the proposed hierarchical control framework improves the lateral path-following performance of four-wheel steer-by-wire vehicles with corner module actuation and enhances steering control flexibility across different driving scenarios.