Sliding mode control with power-type barrier function for autonomous aerial refueling based on disturbance observer

Abrupt disturbances, such as wind gusts, present significant challenges to precise docking control in autonomous aerial refueling (AAR). To address this, this paper proposes a disturbance-rejection sliding mode control (SMC) strategy based on power-type barrier function for a receiver aircraft with multiple control surfaces. First, an estimator-based disturbance observer is developed to enable feedforward compensation for time-varying disturbances while mitigating chattering in SMC, without requiring prior knowledge of the upper bounds of the disturbances or their derivatives. Second, a single-power barrier function-based SMC (SPBFSMC) is introduced to rapidly compensate for disturbance estimation errors under abrupt disturbances, avoid gain overestimation, and ensure that the sliding mode variables converge to a predefined neighborhood of the origin. Furthermore, a dual-power barrier function-based SMC (DPBFSMC) is developed by combining two SPBFSMC methods with powers greater than and less than one, respectively. This approach achieves a smaller final convergence region regardless of the disturbance estimation error magnitude, thereby improving tracking accuracy. Finally, the stability of the closed-loop system is proved using Lyapunov functions, and the effectiveness of the proposed control strategy is validated through simulations.