  This work addresses the landing problem of an aerial vehicle, exemplified by
a simple quadrotor, on a moving platform using image-based visual servo
control. First, the mathematical model of the quadrotor aircraft is introduced,
followed by the design of the inner-loop control. At the second stage, the
image features on the textured target plane are exploited to derive a
vision-based control law. The image of the spherical centroid of a set of
landmarks present in the landing target is used as a position measurement,
whereas the translational optical flow is used as velocity measurement. The
kinematics of the vision-based system is expressed in terms of the observable
features, and the proposed control law guarantees convergence without
estimating the unknown distance between the vision system and the target, which
is also guaranteed to remain strictly positive, avoiding undesired collisions.
The performance of the proposed control law is evaluated in MATLAB and 3-D
simulation software Gazebo. Simulation results for a quadrotor UAV are provided
for different velocity profiles of the moving target, showcasing the robustness
of the proposed controller.
