Unmanned aerial vehicle formation flight via a hierarchical cooperative control approach

Cooperative control is crucial for networked dynamical systems, such as unmanned aerial vehicles in a formation, to respond more quickly and to be capable of working in a cluttered environment. In this paper, a divide-and-conquer hierarchical approach is proposed in three levels to handle the design challenges associated with the mission consensus, different constraints, and precise feedback tracking. In the top level, the algorithm aims to guarantee the macro cooperative behaviors, such as formation consensus of multiple agents under simplified double-integrator dynamics and obstacles. In the middle level, the virtual motion camouflage based algorithm is employed in each individual vehicle to compute the near optimal trajectory considering realistic constraints that the top-level algorithm has to neglect. To enhance the robustness of the trajectory control, a nonlinear feedback controller is used in the bottom level for each vehicle to precisely track the desired trajectory commanded by the middle level. Simulation results demonstrate the formation control capabilities of the hierarchical control strategy under obstacle-laden environments and constraints.