A flexible virtual structure formation keeping control for fixed-wing UAVs

This paper presents a flexible virtual structure (V-S) formation control schemes for nonholonomic fixed-wing UAVs. In contrast to geometric rigid V-S formation control schemes, flexible V-S formation scheme enables a formation to turn smoothly, and hence allows the UAVs in the formation to follow the desired heading profile of the planned formation trajectory. In this work, trajectory generation algorithms are developed to compute the coordinated formation reference trajectories where each of these reference trajectories is executed by our recently proposed trajectory tracking control scheme. Results are also developed to assess the feasibility of the formation trajectory based on operating envelopes of a given UAV. These results provide basic tools for understanding and implementing the formation keeping control scheme according to the fixed-wing UAV´s capability. The effectiveness of the V-S formation control scheme is validated using nonlinear six degree-of-freedom (6DOF) fixed-wing UAV models and simulation results are presented.