A Hierarchical Autonomous Drift Controller for Vehicles with Driving Limits

This study presents a steady-state drift control strategy for rear-wheel-drive vehicles, aiming to maintain stability during drifting when tire saturation and instability pose control challenges. The approach utilizes Model Predictive Control (MPC) and a three-degree-of-freedom(3-DOF) vehicle model, focusing on regulating speed and yaw rate. Due to the unstable equilibrium inherent to drifting and the significant force exerted by rear-wheel drive causing tire saturation, maintaining balance is difficult. We propose a novel approach that couples the lateral and longitudinal forces of the rear wheels, improving vehicle stability by redistributing forces to mitigate tire saturation effects. The control system is designed as an inner-outer dual-loop architecture: the inner loop manages the coupled rear-wheel forces for enhanced lateral stability, while the outer loop ensures accurate path following, which is crucial for effective drifting. Simulation results show that this coupled control approach successfully enables stable drifting and accurate path following, confirming the robustness and effectiveness of the proposed strategy in maintaining vehicle stability under challenging drift conditions.