  We present a fully integrated autonomous multi- robot aerial system for
finding and collecting moving and static objects with unknown locations. This
task addresses multiple relevant problems in search and rescue (SAR) robotics
such as multi-agent aerial exploration, object detection and tracking, and
aerial gripping. Usually, the community tackles these problems individually but
the integration into a working system generates extra complexity which is
rarely addressed. We show that this task can be solved reliably using only
simple components. Our decentralized system uses accurate global state
estimation, reactive collision avoidance, and sweep planning for multi-agent
exploration. Objects are detected, tracked, and picked up using blob detection,
inverse 3D-projection, Kalman filtering, visual-servoing, and a magnetic
gripper. We evaluate the individual components of our system on the real
platform. The full system has been deployed successfully in various public
demonstrations, field tests, and the Mohamed Bin Zayed International Robotics
Challenge 2017 (MBZIRC). Among the contestants we showed reliable performances
and reached second place out of 17 in the individual challenge.
