Video-equipped unmanned aerial vehicles (UAVs) are highly useful in missions of surveillance,
monitoring, and sensing. In these flights, the UAVs must maintain the ability to
see the targets as well as to save energy for prolonged endurance. This paper examines
basic patterns of UAV flights that can maximize its ability to “see” targets or seeability
and/or minimize power consumptions to assist UAV mission planning. In this paper, a
point-mass model is used to describe UAV motions. A seeability model is established
that peaks when the UAV is flying at a certain angle from the normal vector perpendicular
to the surface of the target. UAV flights are formulated as nonlinear periodic
optimal control problems. The performance indices are selected to maximize the average
seeability, to minimize the average power consumption, or to achieve a balance of the
two. Motion constraints due to UAV performance capabilities and safety are imposed.
The effects of different levels of constant wind velocities are considered. These nonlinear
optimal control problems are converted into parameter optimization for numerical solutions.
Extensive numerical solutions are obtained for UAV level flights with constant
airspeeds and variable airspeeds, as well as three-dimensional flights. Clear tradeoffs
between maximum seeability and minimum power are established.