Disturbance-Observer-Based Barrier Function Adaptive Sliding Mode Control for Path Tracking of Autonomous Agricultural Vehicles with Matched-Mismatched Disturbances

In this paper, the path-tracking control strategies are proposed for autonomous agricultural vehicles with unknown matched-mismatched disturbances. First of all, a second-order disturbance observer (DOB) is designed to estimate the matched and mismatched disturbances to mitigate their negative effects. Secondly, by introducing a modified sliding mode surface, a DOB-based first-order sliding mode (FOSM) control scheme is proposed to effectively deal with the system lumped disturbance. To completely eliminate the chattering problem existing in the designed DOB-based FOSM controller, a DOB-based barrier function adaptive sliding mode (BFASM) control strategy is further proposed. The distinguishing feature of the developed BFASM control strategy is that the designed sliding variable can be finite-time stabilized to a predefined neighborhood around the origin, and the upper bound of lumped disturbance does not require to be known in advance. The practical stability of the overall path-tracking system is demonstrated by using the rigorous Lyapunov theory analysis. Finally, some comparative simulations and experiments are conducted to highlight the strong robustness, adaptability, and excellent tracking performance of the developed barrier function-based adaptive path-tracking control strategy.