Wake Vortex Detection with UAV Close Formation Flight

Birds fly in formation to benefit from the upwash wake vortices created by their peer leader. Similar strategies can be employed on aircraft for fuel saving or for range extension. However, further understanding of wake vortices in the near field and mid field is needed for close formation flight (< 10 wingspans). This paper introduces a new method for wake vortex detection using small UAV formation. A NonLinear Dynamic Inversion (NLDI) based formation control law is adapted to the WVU Phastball UAV platform. The designed controller showed good tracking performance during close formation flight (5-10 wingspans) with typical errors of less than 3 meters during straight legs. Then, multiple sensor measurements from leader-follower UAV formation flights were used for the wake vortex detection, including angle of attack, angle of sideslip, accelerometers, and gyros. The collected flight data showed the feasibility of using UAV formation for the wake encounter detection.