Robust controller design and performance of forward-velocity dynamics of UAVs in close formation flight

Study of multi-UAVs(Unmanned Aerospace Vehicles) in close formation flight has drawn attention of late due to the significant advantages in resource mapping at greater swaths, 3-D imaging etc. A study is carried out for controlling two aerodynamically non-identical UAVs in a leader-follower pattern of flight. The study can be for multi UAVs. The aim is to design a robust controller to maintain the relative velocity between two UAVs in longitudinal plane close formation flight, under nominal and large wind related perturbed conditions. The multi variable control of the leading vehicle and its tracking by a follower are initially performed by a PID controller after suitable decoupling and compared with that of a robust H_∞ controller. The modeling includes the effect of leader-trailing-wing vortex on the follower, both for nominal and perturbed system dynamics. The H_∞ controller weights are designed obeying the general rules with mixed sensitivity approach and the robust stability and performance analysis of forward velocity UAV dynamics under different conditions are performed. It is shown that with a well designed robust H_∞ controller one can perform the control and tracking of by follower more accurately and efficiently when compared to a PID controller.