Cooperative formation control for unmanned aerial vehciles (UAV) is a fundamental yet essential component towards to the development of high levels autonomous flight control systems. UAV formation control aims to keep the ground of unmanned aircraft in a designed geometric pattern while avoiding collisions. The capabilities of UAVs can be greatly enhanced when a group of UAVs are deployed, which allows for completing tasks that cannot be achieved by a single vehicle or too costly to accomplish. In the case where the UAVs are formed as a tight formation, the power requirements for following aircraft can be significant reduced, due to the vortices effect of the leading aircraft. However, it also introduces the aerodynamic coupling to the formation dynamics, making the formation control problem even difficult.
Most of the existing works are designed for UAVs with loose formation, which cannot be applied to the problem of tightly flight UAVs, since the vortices effects cannot be ignored when aircraft is flying close to each other. In a recent paper published in SCIENCE CHINA Information Sciences 2017?7?issue, researchers develop a control technique to keep the formation geometric pattern when the UAVs are flying in tight formation, where the interference of the aerodynamic vortices was treated as unknown model parameters/functions to the formation dynamics. It was estimated and suppressed through an adaptive control scheme, which enhance the overall performance of the UAV formation.
Fig. 1 illustrates the proposed formation controller scheme. The leader aircraft shares its motion parameters, i.e., the heading direction and speed to its followers. The follower then estimates the relative positions (x, y) to the leader aircraft based on measured data (ΨW ,VW). The formation controller calculates the motion patterns(Ψc, Vc) for each follower aircraft based on the desired formation distance (xc, yc). The vortices effects to the following aircraft can be defined as the drag incremental factor and lateral force factor, where are assumed as bounded but unknown factors to the formation dynamics.
Though the use of the newly developed control technique, the aerodynamic interference caused by the vortices effect of tightly flying UAVs can be estimated and reduced, thus improving the overall performance of the UAV formation. This research paves the road to achieve a fully automated UAV swarm operation.
See the article:
Wang Y, Wang D B. Tight formation control of multiple unmanned aerial vehicles through an adaptive control method. Sci China Inf Sci, 2017, 60(7): 070207, doi: 10.1007/s11432-016-9092-y