A few co-workers and I at NASA's Marshall Space Flight Center (MSFC) have been working on a small formation flying project over the last 9 months. Our project is to demonstrate formation flying using a decentralized mesh network first by flight testing the concept with small UASes (nearly standard 3DR quads), and then simulating the same system being used on satellites. We had a very successful demo flight last week with 5 quads flying, and I thought now would be a great time to show our results and share our work with the sUAS community.
We've been using 3DR UAS systems for several years now on several projects including an internal NASA search and rescue unmanned system competition and to provide aerial footage of test flights of the Mighty Eagle lunar lander testbed at MSFC.
For this new project, we took the standard quad frame and electronics with Pixhawks as the flight computer and added to that a Beaglebone Black to run our formation logic and a pair of XBee radios to provide the formation communication between our vehicles (which we call nodes). Each node communicates using its two XBees which are each running a separate mesh network for redundancy. The nodes exchange state information that they receive from the Pixhawks (GPS position, etc.) and then use that information to determine where they are in the formation and where they need to go. Since they all share their information, there is no one master or leader of the formation.
We have two primary modes. In the first mode, the vehicles are provided a GPS location and a formation shape which they then fly to and establish a formation. We can change the formation position and shape by sending an update from our ground control station (GCS) using some custom GUIs we developed. In the second mode, we can designate one vehicle as the leader of the formation, and the other nodes will automatically begin following that leader as we move it either via RC or from our GCS.
We've always gotten great help and feedback from this open source community, so we just wanted to return the favor and share the work we've been doing. Here's a video of our latest flight of 5 vehicles. The video has overlays of two of our custom GUIs as well as the audio from our ground control team.