Really powerfull setup, hell of vibrations

Hello everyone. I have a really powerful quad copter:

  • 250mm span
  • 4S 2.6Ah LiPo
  • 6x3x3 Props
  • 2350 KV Motors
  • Pixhawk Cube FC
  • ca. 850g weight

It flies horrible. There is a lot off oscillations on the Roll Axis and some on the Pitch Axis. Do you have some experiences with setting up such a powerful/agile copter? Do you have some PID values to share? Is there a way to set the hover trust value to less then 25% (it is still climbing on that value)?

As usual, without logs it is very hard to help.

There are some guidelines here to start with adjusting the system for small vehicles. Then, some auto-tune.

00-01-01_03-57-02.bin (140.7 KB)
I’m sorry the log is really short, I’m barely able to hover. Hope it provides insight though.

I’ve got a similar setup, auw 880g with four 5x4x3 props, 4s and 1950kv motors and a pixracer.
I had to adjust some filter settings to get it to fly great, but to get less filtering & more speed. If vibrations really are your issue i think fixing it in hardware is the thing to do. Although it is hard to imagine with the dampend cube in there…

You can change it outside the safety margin in missionplanner - > config/tuning -> full parameter list.
MOT_THST_HOVER — 0.** — 0.2 0.8 — Motor thrust needed to hover expressed as a number from 0 to 1
You ony get a warning below 0.2, but you can ignore it.

It wont change the behaviour on rol or pitch, only the throttle stick.

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Try setting these:
INS_GYRO_FILTER to ~60
INS_ACCEL_FILTER to ~30 (you could try default 1st with the above change)

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Thanks for the replies. @dkemxr : The current value for those where notably lower. How does increasing the cutoff frequency lower oscillations?
@Nando : Would you mind sharing your PID values?

The current values are probably default but on small quads a lower filter cut-off will not be responsive enough for stability. I have a 250 size quad also with a PixRacer and it’s rock solid after much manual tuning. Once you have basisc stability you can then try Auto Tune. I didn’t bother just did manual tuning via chan 6 options.

alles doet het maar vliegt niet 30 procent gas2.param (15.0 KB)

PIDs are kinda useless without the rest, pwm rc old-school vs oneshot 125 will not fly the same with the same PIDs and i’m on Dshot right now, not the biggest difference to oneshot 125 in flying i think. And different filter settings change it too of course.
So i attached the full set. Can definitely still be improved and i don’t think it’s what i’m flying with now but they worked.