Approximate Correction of Guidance Commands for Winds

Winds can have a destabilizing effect on parafoil guidance and flight control. This paper will present an analysis that shows how winds affect the guidance loop gain, and several methods are developed for compensating the guidance command for this effect. Exact compensation for winds requires sensing both the wind magnitude and its direction relative to the air speed vector. This requires knowing both the inertial velocity vector and the velocity vector relative to the air mass. The main contribution of the developed approaches presented herein is that they rely only on use of GPS measurements, and are shown to closely approximate the exact solution for a wide variety of flight conditions. Both simulated and flight test results are presented for a typical autonomous parafoil system. Although the emphasis is on application to parafoil guidance and flight control, the methods described can easily be modified so that they can be applied to a wide class of both unpowered and powered unmanned aerial vehicles. I. Backgroun