690 Quad noticing oscilation only during Loiter

(Merkatony) #1

Hello All,

Need your help to figure out the problem i am seeing on a 690 Quad.
Configuration is as follows:
*Tarot frame tested that its stiff enough.
*Pixhawk Cube 2.1
*4014 400kv Motors
*Hobbywing 40amp ESC’s
*Tmotor 1550 CF Props balanced
*TF Mini Plus range finder
*IR-lock
When i started to fly for the first time noticed that default PID was way to high and tuned them up manually to the point that i was able to start Autotune.
All went fine and since this is a well balanced QUAD i simply tuned Roll and copy ATC setting to pitch.
Everything was fine and i had perfect flights on AltHold, until i decided to test loiter mode.
Either on pitch or roll i give a sharp fast move and center stick immediate, i am noticing that the Quad is oscillating a few times above the spot it stopped, i do the same in AltHold and the quad flats out perfectly.
Since then i have done alot more Autotunes and manual tuning, lowering D, and P at a times with no much difference. Run FFT to find i have between 113-120hz a high spike that needs to be worked with a Notch filter (which i run on a previous test and found no difference). And my Z vibes still seem to be on the high side.
Here is a log of me testing filter https://plot.dron.ee/WiCF
Yesterday i run once more Autotune that took about 2-3 minutes for roll and after that i tried another flight https://plot.dron.ee/UBjH and this time same effect was both one AltH and Loiter. For this test i have done the following changes:

  • Timing set to 15degrees on ESC’s
    *ESC braking ON, at the lowest setting,since this is a light quad for its weight and also 15" props

My toughts is to change FILT to 20 from 10 and thinking that if PID shows that its spot on on AltH that it might be related to Loiter Jerk.

Any ideas?

Edit: Also forgot to note that on all my tests, Autotune or Manual i keep noticing that my Roll VS my DesRoll is tracking but inbetween i can see “vibrations?” /“harmonics?” that need to be filtered out, that i dont see on my previous test, where Notch filter was on, but seemed to make no difference on FFT measurements.

(AMV) #2

Hi

May be you can try do the PID “manually”, with this option. Set the channel 6 to one of your knobs from you remote, then you can try LIVE the P, D or I or any value until you get the right one.

This is a video from a guy who did it.

Be carefull because if you go up or down very fast the drone will respond at the same moment and can shake it a lot!

(Merkatony) #3

I did a manual also and on AltH i pretty much stay on the same.
Rebalanced props once more and seems Z vibes lowered more, so i think its power related.
took the filter to 20 from 10 on the ATC and added notch filter.
Seems to be handling good on both calm and strong wind so far, but this gives mostly a weird control feeling.
Since its overpowered, might be related with Throttle Rate.