Ok. I'm just about to rip off this M8N unit and toss it into the gulf of mexico. Nothing but issues. GPS acquisition is phenomenal - typically 15 to 20 satelites....sitting in my living room. The issue is that &%$ compass.
Symptoms:
- Stable Loiter about 10% of time.
- Incessant toilet-bowling.
- Compass EKF OK (well in the green) so long as I keep the quad pointing north. When I turn the quad the compass heading changes in Mission Planner, but by the wrong amount. Compass EKF goes full scale red and doesn't come back down unless I reorient the quad to the north. Even then Mission Planner isn't showing it to be pointing north but rather offset by 20 to 30deg. If I give it enough time it eventually sorts itself back out again to North.
1) I've checked the orientation of the M8N to the frame and it's fine. I've checked the orientation of the M8N board inside it's housing and it's fine (arrow on the circuit board lines up with arrow on top of housing).
2) Compass is mounted on a 6" pedestal at the rear of the quad and well away from any electrical noise. (It's a 680mm frame).
3) I've calibrated the compass a dozen times now and my offsets are in the range of -24 3 -304 (yeah, the Z-offset is a little on the high side but I haven't been able to sort that out. The pedestal is a folding aluminum/carbon fiber unit and doesn't have any ferrous items on it.
4) I ran CompassMot and my electrical interference is about 8% or less.
5) For shits and giggles I mounted a 6cm x 6cm copper plate under the M8N to see if this might have an effect on compass heading. No effect.
6) My HDOP is consistently 0.80 or lower - even with the Compass EKF pegged in the red and Mission Planner blaring "Compass Variance" at me.
What am I doing wrong here? Is this normal behavior for the M8N? Does the Compass EKF always spike when not pointing north or is it supposed to stay in the green no matter what heading the compass is pointing?
I would appreciate any and all help. Worst case I try a different compass as this one seems to be jinxed. I've ran the quad through a couple Autonomous flight plans and it worked fine. However, unless I get the Loiter toilet-bowling issue sorted out I'm not going to run it autonomously again.
Thanks all!
- J
Replies
i have a few M8N, never had any issues like that, specially with compass....try the "relaxed" setting on arducopter for the compass sensitivity, I believe is somewhere on the EKF settings forgot exactly where
I've verified that the Pixhawk is indeed using the external compass in the M8N as well and not the internal one. (Compass readings in Mission Planner change once I get a magnet within 3ft of the M8N)