New build tune problem 5" racer voxl2

Flight Testing & Log Analysis v1.12
1

hi guys
i recently build custom drone 5" racer style .
the arms sitting between 2 alloy plates , rear arms made from alloy as well and the front arms printed in sls printer(sort of plastic ).
i founded very frustrated to tune it , it keeps wobbling no matter what i tried …

my last chance is to show you the log if you find something that could cause it .
the flight computer is modalAi voxl2 1.12.3 px4 firmware .

https://review.px4.io/plot_app?log=e465062c-95c1-43f8-99a1-ac3e5dfba4f5
any help will be much appreciated .

2

Hi @ben,

What exactly are the type of oscillations that you are getting? Is it high or low frequency?

  1. From the Actuator Outputs graph you can see that motors 2,4 requires more current, which may suggest that the C.G is not in the middle of the frame.

  2. There is a pretty strong correlation between the thrust and magnetic field, which may cause a bad yaw estimation. You can try to do the Compass Power Compensation.

Best,
Iftach.

3

Thanks @iftahnaf for quick reply,
It’s pretty low frequency oscillating ,
Looks like more on roll axis , it’s standing pretty much ok on mid air .
but you can see it wobbles periodically on roll axis .
My workaround so far was to make reinforcement to the arms , changing fc dumpers, changing props .

I will try to upload video later
:pray:t2:

4

You can try to reduce the I gain in the roll rate to see if it helps, as written in the PID Tuning Guide:

  • If the I gain is too high: you will see slow oscillations.

We had the same problem with a bigger drone (slow oscillations) and reducing I gain on the rate controllers solved that issue.