Observer-Based Finite-Time Dynamic Encirclement for Multi-ASV Systems Using Time-Varying Sliding Mode Control

Dynamic encirclement is a strategy employed to maintain ongoing monitoring or neutralize a target by restricting its range of movements. This paper proposes a novel approach to handle finite-time dynamic encirclement problems for multiautonomous surface vehicle (ASV) systems. To be consistent with the actual task scenarios, each ASV faces challenges such as model uncertainties, unavailable velocities, saturated inputs, and external disturbances. Specifically, a fuzzy logic system (FLS) is utilized to approximate the nonlinear dynamics, and an adaptive fuzzy state observer is designed to estimate the unavailable velocities of the multi-ASV system. Next, a time-varying sliding mode controller is developed based on a time-varying formation function. In order to prevent singularity, the system is divided into two zones. A terminal sliding mode controller and a linear auxiliary sliding mode controller are assigned to each zone, respectively. Then, by applying finite-time theory, the dynamic encirclement issues of multi-ASV systems can be addressed within a finite time. Finally, the effectiveness of the obtained results can be verified by the Lyapunov theory and simulation examples presented.