I’ve seen some great feedback from this forum, so I thought I’d make a post here. I’m looking to take my quads from flying OK to dialed-in and I really don’t have the depth of experience to know what is needed to make that happen.
For some background, I’m a researcher with the University of New Mexico where I’m using Computer Science to study volcano plumes using a swarm of large quadrotors. The quads we’ve built have 18" arms, use ardupilot on a cube black, along with some large T-motor motors, ECs, and 22" props. The whole quad is designed to fly up to an hour in order to collect gasses above an active volcano. Additionally, we’ve set up a network so that our 5 quads can talk to each other and coordinate their flight - meaning we can fly them in-formation as a single unit or fly them independently and have them trade data. Pretty exciting stuff!
My goal is to make our quads as stable as possible to prepare them for the adverse conditions we may see on the top of a mountain. This would include gusty or high wind scenarios. So, that our automated flights will have their best chance for success.
What we’ve done so far is the following:
- Autotune - we’ve relied heavily on autotune on a single quad to set the PIDs. We adjusted the D parameter up a bit following some analysis of the logs (up from 0.001 to 0.005) for some better response out of the quad. We copied this autotune to the rest of the quads in the swarm.
- Vibration dampening - we’ve combated vibration using a vibration gel under the flight controller and added some weights to the top of the cube to help in this regard. This significantly reduced vibration.
- Setup a static not filter - this took vibration down from sometimes touching 30 to under 10 almost always and seems to make the quad behave better. The RPM we setup to filter is 48hz.
What we’re seeing now is sometimes the quad has some erratic behavior. First, in gusty winds, we see the quad overcorrecting or oscillating in a scary fashion - well, almost any drastic mauver is scary for a large quad. This leads me to believe we’ve set the D parameter too high, or it’s not balanced with a proper P parameter. Second, when flying over bushes, the quad changes elevation in an extreme way, meaning that we see the quad bounce around due to (what I can only guess is) lidar inputs. Again, it seems like the quad is over-reacting to inputs instead of smoothly reacting to inputs.
So, I’m reaching out for help. Here are two recent example flights:
This is a baseline tune that we run on all our quads:
And the flight log for this: https://drive.google.com/file/d/1ehyKYq1NGAG_BOcGcj7nZ6WXhreKBI8f/view?usp=sharing
This is a recent retune with a higher aggressiveness setting:
And the flight log for this: https://drive.google.com/file/d/1CPsQ4bobxN5jHxSHNQqtIzmb20u3vqVY/view?usp=sharing
What should I do next to tune the quads? If more data or a certain flight would help, I’m game to fly it.