Strange Roll behavior in stabilize mode

Log Analysis -- deprecated Copter Logs -- deprecated
1

Equipment: Standard quadcopter with APM1

Hello,
After the update to v3.1 I found following strange behavior:

I hovered and I gave some impulses to the transmitter roll axis in order to check the PID quiality.
Please see the attached sreenshot from the log (RollIn:red and Roll:green), after some RollIn impulses the copter suddenly leaned strongly to the opposite direction (40°).
[attachment=0]Crazy_Roll_.jpg[/attachment]
This behavior can be reproduced. I tried it with different Rate PID settings (No D, No I, LowP, highP, HighD, HighI).
I didn’t try this with the former used version 2.7. So I don’t know, if this bahavior is connected with the software version.

Can someone explain this?
Can someone give me a hint, which parameters can I change to avoid this behavior?
I have attached the complete Log (see at line 12500).

Thanks in advance.

2

[quote=“diyohl”]Equipment: Standard quadcopter with APM1

Hello,
After the update to v3.1 I found following strange behavior:

I hovered and I gave some impulses to the transmitter roll axis in order to check the PID quiality.
Please see the attached sreenshot from the log (RollIn:red and Roll:green), after some RollIn impulses the copter suddenly leaned strongly to the opposite direction (40°).
[attachment=1]Crazy_Roll_.jpg[/attachment]
This behavior can be reproduced. I tried it with different Rate PID settings (No D, No I, LowP, highP, HighD, HighI).
I didn’t try this with the former used version 2.7. So I don’t know, if this bahavior is connected with the software version.

Can someone explain this?
Can someone give me a hint, which parameters can I change to avoid this behavior?
I have attached the complete Log (see at line 12500).

Thanks in advance.[/quote]

This kind of thing is generally hardware. Look at this graph - it’s always pitching forward and rolling right. Check the front-right motor.

3

Hello jschall
thank you for the analysis and the hint concerning the hardware. It was a plausible issue, because the ball bearings of some motors have been very very bad.

So,

  • I ordered and mounted new motors (1100kv instead of 950kv).
  • I removed cameras and FPV transmitter.
  • And I tried it again. Hovering at 30 cm height and giving pulses to the transmitter roll axis.

[attachment=2]strange_roll_2nd.jpg[/attachment]

The effect is the same (see at line 6300). I think, this effect appears in both directions and also with pitch pulses.
I attached

  • a new log,
  • a picture with the strong roll reaction of the copter
  • and a analysis roll-rollIn and pitch-pitchIn similar to your analysis. Looks this ‘roll-rollIn and pitch-pitchIn’ graph better than the old one? (I can’t judge it.)

[attachment=1]strange_roll_2nd_diff.jpg[/attachment]

What can I do as next? I have no confidence to fly the copter higher.

  • Something with ESC or ESC calibration?
  • Is the reason possibly the gruond effect in 30cm height?
  • Should I use the APM2.5 board instead of APM1?
4

The solution is quite simple.
ESC calibration has not been complete.
Apperrently the motor output signal fell below zero baseline of ESC input during attitude control.
Consequence: Delay of power increase and stability problems.
So the advice to check the hardware was correct.
Thanks for your help,
Jens

5

[quote=“diyohl”]The solution is quite simple.
ESC calibration has not been complete.
Apperrently the motor output signal fell below zero baseline of ESC input during attitude control.
Consequence: Delay of power increase and stability problems.
So the advice to check the hardware was correct.
Thanks for your help,
Jens[/quote]

Ahh, yes that can happen. Will start mentioning it.