Collective Circumnavigation

This paper considers the problem of localization and circumnavigation of a slowly drifting target with an unknown speed by a group of autonomous agents while they form a regular polygon at a known distance from the target. The goal is achieved in a distributed way where each of the agents coordinates its motion knowing its own position and either the bearing angle of the target or the distance to the target, and the position of one of its neighbors. First, we solve the problem for the case where the target is stationary and propose a two-stage control law that forces the agents to move on a circular trajectory around the target and form a regular polygon formation. Then, we consider the case where the target is undergoing a slow but possibly persistent movement. Later, we consider the case where only one of the agents know the desired distance from the target. In the end, the case in which only a subset of agents can measure either the bearing or the distance to the target is considered. The performance of the controllers proposed is verified analytically, through simulations, and in an experimental setup.