Strange Motor Behaviour...PID?

[stud]

Gentleman,

I hope I'm in the right section of this forum. Sorry if not!
In the video below, you see that my X8 coaxial octo runs up. There is no oscillation or instability, but just before lift off, one (random!) or more engines suddenly get very fast (diverge), hit the current limit of the ESC and stop. This happens if the octo is hanging from the ceiling (like in the video), or stationary on the ground.
https://www.youtube.com/watch?v=Lwr7lre ... e=youtu.be
[youtube]Lwr7lrelwLw&feature=youtu.be[/youtube]

What I've done:
-All ESC32 are calibrated with 13Amps and the Global limit is set to 15Amps. I tried 20 Amps, but that just causes a stronger tilt. I think the problem is not the CL calibration, the problem is why do they run up so fast at all?
-Trial and Error with the PID settings of the AQ6. I isolated every parameter and set to zero indepentently and it still happened

What I think it might be:
-ESC32 PID? So far I used default
-Interferece between AQ6 and ESC32 PWM signal caused by three-phase cable between ESC32 and motors
-I dont know, please help

Setup
Rosewhite X8 coax
AQ6 post Oct14
ESC32
4S 4400mAh
MN3510 630kV
13x4.4 CarbonProps (T-Motor)
Immersion RC LongRange UHF with Futaba 14Chnl

Thank you for your help!

Dominic

[aBUGSworstnightmare]

[stud]

Thank you Joerg, some very good, experience based suggestions!
-So I will recalibrate the CL with the values you stated. What do you mean by "not able to calibrate 13x5.5 with good results"?
-I have the DIMU, tare and MAG calibration is done and stored, no calibso or temp compensation
-The DIMU baro is shielded with foam, the AQ6 baro is not (is that a problem?)
Picture of the setup
https://www.dropbox.com/s/l9sqrq73xdsio ... 133408.jpg
Could it be the interferece? Because the PWM signal cables are pretty close to the Motor Cables

Thank you

[aBUGSworstnightmare]

[chschmid]

Hi Dominic

I agree with Joerg about the calibration of the ESC's.
Nevertheless I would double check the motor mixing table. Looking at you vid, I am not sure what comes first. And the X8 should stay level with one motor off.
What I had in build with the ESC'S out at the motor mount was a screwed PWM signal as soon a the amps went over 10A. A shielded PWM line did the trick.

Cheers

Christof

[bluuu]

[stud]

Thank you for your inputs!
I will do the CL calibration (by using your values, Joerg, i mean the 22/23Amps, not your calibration table) tomorrow.
I am sure that the motor mixing table is correct. About what comes first:
1. stable run up of all 8 engines
2. one engine "goes crazy", gets very fast and
3. it hits the current limiter
4. octo tilts
5. i shut it down
Where the core of my problem is nr.2. Nr. 3 is just a consequence
And then I'll see if the shielded PWM do the trick. Thanks again, I'll update tomorrow

[bluuu]

Do some logs. It may help a lot.

[aBUGSworstnightmare]

[chschmid]

Hi Dominic

The current limiter is not shutting off the ESC. It is limiting the current. Why the motor goes out of sync and shuts down has another reason. The "going wild" ect. sound like what I had with the PWM lines.
Why not using CAN?

Cheers
Christof