Autonomous Formation Flight Control System Using In-Flight Sweet-Spot Estimation

A formation flight control system that addresses the unique environment encountered by aircraft flying in formation and in the upwash of the leading aircraft that leads to a scenario with minimum induced drag at the trailing aircraft (sweet spot) has been designed. To test the control system, a simulation environment that adequately represents the aerodynamic coupling effects between aircraft flying in formation and implements an incremental nonlinear dynamic inversion-based formation flight control system has been created. Since the exact position of the sweet spot is not known or measured, the research presented in this paper uses an advanced extremum-seeking algorithm that uses an extended Kalman filter to estimate the wind gradients to automatically steer the trailing vehicle toward the sweet spot. Monte Carlo simulations for two and three aircraft formations have shown that the algorithm has the ability to consistently find the sweet spot and is robust to errors due to turbulence.