Coordinated Strategy of Trajectory Tracking and Stability Control for Autonomous Vehicles with Switched Envelope and Composite Evaluation

<div>Trajectory tracking and lateral stability under extreme conditions are critical yet conflicting control objectives due to nonlinear tire dynamics and road adhesion limitation, where accurate characterization of vehicle dynamics for each objective is essential to enable coordinated performance. This article proposes a coordinated control strategy based on switched envelope and composite evaluation to improve both tracking accuracy and stability. Unlike previous stability envelope methods that rely solely on the vehicle’s rear tire saturation boundary to prevent instability, the switched envelope approach incorporates both front and rear tire saturation boundaries to simultaneously mitigate steering loss and instability in trajectory tracking. A critical steering angle, derived from tire slip dynamics and phase plane stability analysis, is formulated as the switching criterion. Additionally, a composite stability evaluation is developed by combining a future disturbance resistance index with the current stability utilization metric, providing a comprehensive measure of vehicle control capability and preventing frequent oscillations among control objectives. Integrated with a switched envelope model predictive control framework, it enables adaptive adjustment of state constraints and control weights to dynamically balance trajectory tracking accuracy and stability. Finally, co-simulations using CarSim and MATLAB/Simulink, along with hardware-in-the-loop experiments, demonstrate the effectiveness of the proposed strategy in enhancing vehicle handling and stability under severe driving scenarios.</div>