Hierarchical Flocking Control Strategy for Underactuated Autonomous Surface Vehicles with Integrated Obstacle Avoidance

This paper introduces a hierarchical flocking control strategy for underactuated autonomous surface vehicles addressing nonlinear dynamics, environmental disturbances, and obstacle avoidance. The proposed framework integrates high-level flocking, mid-level path-following guidance, and low-level dynamic control that explicitly manages actuator saturation. This hierarchical framework ensures cohesive group behavior, smooth transitions between control layers, and bounded control actions. Simulations using the CyberShip II model validate effectiveness, demonstrating minimized tracking errors and successful collision avoidance. The results highlight the robustness and applicability of the proposed approach for coordinating multiple underactuated autonomous surface vehicles in realistic operational scenarios with constrained propeller power.