Visual Tracking in Wind with Field of View Constraints

This paper addresses the problem of tracking a ground-based target with a fixed camera pointing out the wing of a micro air vehicle that is subjected to constant wind. Rather than planning explicit trajectories for the vehicle, a nonlinear image-based feedback guidance strategy is developed that maintains the target in the field-of-view of the camera. We show that under ideal conditions, forcing the target to the center of the image results in flight paths that are elliptical trajectories. We also show that if the target is allowed to move in the image plane, circular orbits are possible. Both simulation and flight tests are used to demonstrate the effectiveness of the proposed algorithm and its robustness to wind gusts. Nomenclature Mathematical symbols are listed in the order that they are used in the document. ρ Range to target η Bearing to target Va Airspeed Vw Wind speed ψ Heading angle of aircraft χw Wind direction g Gravitational constant (9.8 m/s) φ Roll angle αe Elevation angle of optical axis η ̄ Bearing limit imposed by field-of-view constraint h Altitude φ ̄ Roll angle limit imposed by field-of-view constraint ϕ Deviation of optimal axis from line of sight vecto