A Hierarchical Strategy for Real-Time Tracking On-Board UAVs

In this paper, we present a real-time tracking
strategy based on direct methods for tracking tasks on-board
UAVs, that is able to overcome problems posed by the challenging
conditions of the task: e.g. constant vibrations, fast 3D
changes, and limited capacity on-board. The vast majority of
approaches make use of feature-based methods to track objects.
Nonetheless, in this paper we show that although some of these
feature-based solutions are faster, direct methods can be more
robust under fast 3D motions (fast changes in position), some
changes in appearance, constant vibrations (without requiring
any specific hardware or software for video stabilization), and
situations where part of the object to track is out the field of
view of the camera. The performance of the proposed strategy
is evaluated with images from real-flight tests using different
evaluation mechanisms (e.g. accurate position estimation using a
Vicon sytem). Results show that our tracking strategy performs
better than well known feature-based algorithms and well known
configurations of direct methods, and that the recovered data is
robust enough for vision-in-the-loop tasks.