Flexible Structure Control Scheme of a UAVs Formation to Improve the Formation Stability During Maneuvers

Abstract

Abstract:One of the issues related to formation flights, which requires to be still discussed, is the stability of formation flight in turns, where the aerodynamic conditions can be substantially different for outer vehicles due to varying bank angles. Therefore, this paper proposes a decentralized control algorithm based on a leader as the reference point for followers, i.e. other UAVs and two flocking behaviors responsible for local position control, i.e. cohesion and repulsion. But opposite to other research in this area, the structure of the formation becomes flexible (structure is being reshaped and bent according to actual turn radius of the leader. During turns the structure is bent basing on concentred circles with different radiuses corresponding to relative locations of vehicles in the structure. Simultaneously, UAVs' airspeeds must be modified according to the length of turn radius to achieve the stability of the structure. The effectiveness of the algorithm is verified by the results of simulated flights of five UAVs.

Distributed sliding mode control for leader‐follower formation flight of fixed‐wing unmanned aerial vehicles subject to velocity constraints

“…However, as a special type of robots, fixed‐wing UAVs have some special properties owing to its special dynamics. Firstly, the dynamics of the fixed‐wing UAV is an under‐actuated system and its kinematics can be simplified into a unicycle system 29 . In addition, the fixed‐wing UAV can neither move backward directly nor slow down the linear velocity lower than a certain positive value, namely, it is required to maintain a positive minimum airspeed due to the stall conditions 30 .…”