  Autonomous Unmanned Aerial Manipulators (UAMs) have shown promising
potentials to transform passive sensing missions into active 3-dimension
interactive missions, but they still suffer from some difficulties impeding
their wide applications, such as target detection and stabilization. This
letter presents a vision-based autonomous UAM with a 3DoF robotic arm for
rotational grasping, with a compensation on displacement for center of gravity.
First, the hardware, software architecture and state estimation methods are
detailed. All the mechanical designs are fully provided as open-source hardware
for the reuse by the community. Then, we analyze the flow distribution
generated by rotors and plan the robotic arm's motion based on this analysis.
Next, a novel detection approach called Rotation-SqueezeDet is proposed to
enable rotation-aware grasping, which can give the target position and rotation
angle in near real-time on Jetson TX2. Finally, the effectiveness of the
proposed scheme is validated in multiple experimental trials, highlighting it's
applicability of autonomous aerial grasping in GPS-denied environments.
