NLDI guidance control laws for close formation flight

This paper presents identification, control synthesis and simulation results for an YF-22 aircraft model designed, built, and instrumented at West Virginia University. The goal of the project was the experimental demonstration of formation flight for a set of 3 of the above models. In the planned flight configuration, a pilot on the ground maintained controls of the leader aircraft while a follower aircraft was required to maintain a pre-defined position and orientation with respect to the leader. In this paper, the identification of both a linear model and a nonlinear model of the aircraft from flight data is shown first. Then, the control laws, that feature a linear inner loop controller and a NLDI (nonlinear dynamic inversion) based outer loop guidance controller, are discussed in detail. Finally, both simulation and flight test results are presented.