Pixhawk [2.1] Firmware [3.5.2] - Wobbles and out of control

Hardware Pixhawk 2
1

Hi guys,

I am trying to set up my new Pixhawk 2.1 board, but when I try to fly it is so wobbly and becomes out of control.
When plugged on the computer, I sometimes have the warning Bad Gyro Health.

Here is what I tried to do without any success:
Flash another type of vehicle and reflash 3.5.2 quad firmware
De-activate the GPS
Lower the PIDS to minimum
Tried the board on another functional quad
Change battery, it worse with a 4S one than with a 3S
Calibrate successfully a few times the ESCs

I have also noticed the light below the cube is not green when powered, is this showing an issue?
Here is the log of my lastest try where I lost control and crashed 2m away from me…
2017-09-20 10-07-30.log (225.4 KB)

Anyone has ran into this crazy wobbling issue?

2

Why did you lower the pids to minimum? Have you tried flying with defaults?
Crazy wobbling is either bad tuning or bad vibrations.

3

Yes I first tried to take off with normal PIDs values, but it is really bad, I cant even fly…
I tried to lower them down to see if it improved, my quad is a 280mm, smaller than everyone else I guess.

4

Set your gains to 1/3 default and raise your filter values to 30 or 40, then see if it is flyable. If it is, do a pos hold autotune.

5

the log is a bit too short to tell something useful. Are you able to post a longer log?

6

I have done the firmware upgrade to 3.5.3, set gains to 1/3 and raised up filter values to 30.

Here some updates (not necessarily linked to the changes IMO)

5” props + 3S battery = No oscillations ( or not noticeable)
5” props + 4S battery = No oscillations ( or not noticeable)
6” props + 3S battery = bad oscillations
6” props + 4S battery = very bad oscillations to control loosing.

And here is a video of what happening on 6” props + 4S:
Link to video
https://www.dropbox.com/s/jzox76u999ov5ap/IMG_0288-short.mov?dl=0

Any other idea? I will post a longer log of the bad setup soon.

Thank you!
Antoine

7

for the 6"/4S setup, half the gains yet again, then try poshold autotune. You may have to increase the filters again: do this incrementally (10Hz at a time), but you want this figure as low as possible so try decreasing the gains and autotuning first.

8

Also: vibration isolation for the flight controller! Just a little, but it really does help.

9

Sorry stupi question…
How can i lower the gain ?

Thanks in advance.

Kind regards: Jan

10

Here are the PID values I manually tuned on a 210 mini quad with a soft mounted PixRacer. I’m not suggesting you copy them its just to give you an idea of the direction you will likely have to take with respect to Rate Roll/Pitch PID and filter.

210 params.JPG939×523 75.3 KB

11

On the advanced tuning page in missionplanner is easiest if using windows. Read the wiki on tuning though - it’s pretty useful.