A Two-Stage APF-Pheromone Cooperative Search and Encirclement Method for Multi-UAV Target Capture in Obstacle Environments

Cooperative search and encirclement of a maneuvering target by a group of unmanned aerial vehicles (UAVs) in cluttered environments is a challenging problem because searching, obstacle avoidance, and encirclement impose conflicting objectives on a single controller. In this paper, we propose a two-stage cooperative control framework that combines a pheromone-guided distributed search strategy with an artificial potential field (APF) based cooperative encirclement strategy. In the search stage, a globally shared pheromone map drives the swarm away from repeatedly visited regions while stochastic exploration terms and boundary-aware repulsive fields prevent clustering and collision. Once any UAV detects the target within a sensing radius, the swarm switches to the hunt stage, in which one UAV is assigned as an interceptor that blocks the escape direction towards the boundary while the remaining UAVs distribute themselves uniformly around the target using an adaptive angular allocation rule. The method is validated in a$10 \mathrm{m} \times 10 \mathrm{m}$indoorscale simulation arena with six quadrotors. Experimental results over twenty randomized trials show a 100% detection success rate with an average detection time of 16.7 s and a capture success rate of 92%.