Adaptive control of UAVs in close-coupled formation flight

This paper studies the control of multiple UAV's flying in a close-coupled formation for the purposes of drag reduction. A controller design methodology for use in the trail vehicle in a two-UAV formation is presented. The LQR outer-loop tracks relative position commands and generates body-axis rate commands for the inner loop. The adaptive dynamic inversion inner-loop tracks these input commands using only minimal knowledge of the aircraft dynamics. The controller is tested in a two-vehicle formation flight simulation. Excellent command tracking and performance are achieved without use of specific knowledge of the formation flight effects. Simulation results demonstrate that the proposed controller design enables the trail UAV to maneuver in the lead UAV's wake, and to hold a desired position in the vortex.