A formation keeping feedback control for formation flight of UAVs

When executing a sharp maneuver, if the formation maneuver path is not well designed, a formation of UAVs constrained by their performance capabilities, may not be able to keep in satisfactory formation as desired. We, applying Lyapunov stability theory and using virtual structure approach, propose designing individually a nonlinear controller for satisfactory formation keeping. Then, by applying nonlinear model predictive control approach, a trajectory tracker with formation feedback is designed to improve the capacity of formation keeping during a sharp maneuver. Formation feedback is achieved by adding a formation-error cost to the total cost function, and a dynamic parameter is proposed to obtain a trade-off between formation keeping and flying along prescribed trajectory adaptively. Each UAV gets the reference commands of the virtual structure by solving a Finite Horizon Optimal Control Problem at each time step. Simulation results and their analysis suggest that, compared with situation without formation feedback, the designed trajectory tracker with formation feedback can reduce formation-keeping error evidently.