Local and asymmetrical potential field approach to leader tracking problem in rigid formations of fixed-wing UAVs

The paper presents a novel approach to a position control problem in rigid formations of nonholonomic unmanned aerial vehicles (UAVs), such as fixed-wing aircrafts. In the most known approaches of artificial potential fields applied in swarm robotics, it is assumed that the potential fields usually reach a zero or minimal magnitude at desired positions of UAVs in the formation, i.e. a steady state, since they are usually defined as a spherical function of positions errors. This is not feasible for fixed-wing UAVs, which have limited turn radius and minimum flight speed securing them against a substantial loss of lift force. Therefore, at the stationary state of the formation, UAV should reach speed and heading angle of a reference point defined as a real or virtual formation leader. To achieve this, a new asymmetrical local potential field is proposed in the paper. It will steer UAV in the formation flight in the way that makes its airspeed and heading angle asymptotically tending to the airspeed and the heading of the leader, according to the decrement of its position error. This guarantees both a precision of position tracking and stability of flight of each UAV as well as entire formation. Moreover a simplicity of this approach allows implementing it easily into real UAVs.