Finally got my coaxcopter flying! But I need some help with tuning

Hi everyone! I’ve been working on my 9in coaxcopter design for over a month now on and off. It’s gone through a few changes, starting out with underpowered motors with ancient 3Drobotics ESCs, it now has a ~2:1 TWR, and it’s gone from using normal control surfaces to grid fins. Just now I got it flying. But as you can see from the video, not very well.

Pitch, throttle, and roll response are all pretty good, but yaw response is borderline nonexistent. Very obviously for manual control, but also likely for the auto stabilization as it seems to have no way to exit a spin automatically. And it really really likes entering a spin, it takes a lot of full stick in the opposite direction to get it to stop.

Secondarily, it drifts around a lot, but this is easier to compensate for when it’s not spinning.

I’ve calibrated the ESCs, and I already messed with the PID a lot, and it spins less than it used to. The PID could still be the problem as I have absolutely no idea what I’m doing, and I put a lot of the terms higher than they probably ever should be.

If it could be an issue with my design, here’s some photos:

Excuse the wiring and duct tape, the ESCs were getting toasty inside the body so I had to make some changes.

Any ideas for how to make this fly better? Is it possible to run an autotune in its current state? Go easy on me, I’m new to this.

Nice post. Good photos, but no FW version information and no .bin log file. How can we help you without having that?

This is Copter V4.4.0 I’ll add some logs. I’m not very familiar with this, but I don’t seem to have any .bin logs, only .tlog. If there’s a way to get these in the right format, please tell me and I’ll send the right type.

Please search this forum. We constantly explain how to get the .bin log files.
And post on the correct forum section. You posted on the 4.0 section. There is a 4.4 section. I will correct that.

And welcome to the comunity

IDK if you are using a pixhawk or cube, but if you are, you just need to remove the sd card and read the card and finding the file that matches the date of the flight. you can use mission planner to extract the bin file.

I’m running a mateksys F405 VTOL with no SD card because it wasn’t reading it. I tried a few different cards and messed with the settings, but it wasn’t having it.

Ah, I should have said earlier. I don’t have an SD card in as the autopilot wasn’t able to detect that there was one in. Possibly a hardware issue but I figured telemetry logs would be good enough for my testing. Am I right to assume that the .bin logfile would need be accessed via SD card?

If it’s really important, I can try debugging why the SD slot wasn’t working, and then I can fly again?

if I am not mistaken, unless the sd is properly set up and able to log and store the bin files, wouldn’t that be a pre arm check that would block the arming?

They are not and yes you need an Sd Card for useful flight logs.

I tried to fix the SD issue for like an hour and then I just disabled the prearm check for that.

Dang I hope I don’t need to buy a new autopilot. I’ll try setting that up again.

Put the settings back to default and format a decent Sd card before use.

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Probably not. Try a good SD card. The cheap ones that are so common now are usually half the problem. For logging it doesn’t need to be anything big or super fast, just good quality.

Ok, I got the logging working properly. It turns out that it fixed itself since I last tried it. And I never took the SD card out! The dates on the logs were messed up which is I think why I was confused, but I think I probably have the right ones after a cursory look over them.

When the dates are messed up like that it usually means you don’t have a GPS lock, or working GPS.

Ah ok, that would make sense, these tests were indoors.

That compass is going crazy on there. You should run MagFit to get a better calibration on that compass.

I’ll definitely try this right now!
Does this explain the super sluggish yaw response though? Manual control has basically no say in its angle for the yaw axis.

Here’s the log for a flight with the recalibrated compass. It seems to have helped reduce the initial spinning when you don’t use control inputs. But once you start trying to move around, unwanted angle error builds up and eventually it starts spinning. This time there was a forced disarm because it stopped responding to throttle, so I had to disarm it before it flew away. This occurred after a particularly bad spin. I also experienced a sort of “death wobble” when trying to counteract the spin with sticks, which I don’t really understand either.

I got some logs now. Any ideas?