Multirotors are underactuated, thus controlling interaction with the environment such as aerial manipulation has some problems. However, although these problem can be addressed using multi-DOF actuators or some novel control techniques, multirotors suffer from short flight time and limited payloads.
The video below uses a spherical joint to connect multiple quadrotors to the structure and use each quadrotor as rotating thrust generator.
This way the quadrotors may benefit both in flight time and payload capacity while maintaining the agility of the quadrotor. Some groups have also used tethers to use multiple quadrotors on a single aerial platform.
I am interested in implementing this system using the APM flight stack to fly outdoors. However, it seems that APM does not support attitude control on ROS. Curious why px4 supports attitude set point topics but not APM.
Comments
@Jaeyoung,
It should accept the SET_ATTITUDE_TARGET message (see support in ardupilot here) but perhaps the vehicle's not in GUIDED mode or maybe it's because it went in after the Copter-3.3.1 release so the only way to use it is to use master?
@Randy
Thanks, I am using mavros, which sends mavlink messages for commands. However, it seems that APM does not support attitude control commands via MAVLink. It seems like PX4 allows commands via mavlink though not APM. Is there a specific reason that APM is not allowing attitude or rate commands via mavlink?
Jaeyoung,
Cool.
Ardupilot works with ROS in a simulated environment and I'm pretty sure that someone has written a ROS<->ardupilot library. It's not heavily used so I imagine it would take some work to get it working but if you're interested in doing that, please ping us on the drones-discuss@googlegroups.com email list or on Gitter.