Nonlinear adaptive close formation control of unmanned aerial vehicles

This paper treats the question of formation flight control of multiple unma nned aerial vehicles (UAVs). In close formation the wing UAV motion is affe cted by the vortex of the adjacent lead aircraft. The forces produced by th ese vortices are complex functions of the relative position coordinates of the UAVs. In this paper, these forces are treated as unknown functions, For simplicity, it is assumed that the UAVs have autopilots for heading-, alti tude-, and Mach-hold in the inner loops. An adaptive control law is derived for the position control of the wing aircraft based on a backstepping desi gn technique. In the closed-loop system, commanded separation trajectories are asymptotically tracked by each wing aircraft while the lead UAV is mane uvering. It is seen that an overparametrization in the design is essential for the decentralization of the control system. These results are applied t o formation flight control of two UAVs and simulation results are obtained. These results show that the wing UAV follows precisely the reference separ ation trajectories in spite of the uncertainties in the aerodynamic coeffic ients, while the lead aircraft maneuvers.