LibrePilot Forum

Users => Vehicles - Fixed Wing => Topic started by: DocHardinger on January 26, 2017, 05:52:35 pm

Title: Roll oscilating
Post by: DocHardinger on January 26, 2017, 05:52:35 pm
I added a CC3D to my acroplane see here: https://forum.librepilot.org/index.php?topic=2984.0 (https://forum.librepilot.org/index.php?topic=2984.0)
When i fly really fast in Attitude mode it begins to wobble in Roll Axis...
I reduced the P Value to 6 then its better but not gone...
Anyone got an idea how to tune PIDs correctly or are there any other ideas how to solve this?
I balanced prop and motor as best as i can, Vibrations are not too high, i think.
And happened also with low motor speed, just falling down with high speed also produces wobbling...

Thx in advance
Title: Re: Roll oscilating
Post by: TheOtherCliff on January 26, 2017, 06:18:42 pm
I had oscillation in pitch when doing fixed wing with CC3D a long time ago.

One solution is to reduce your roll PID (reduce both P and I by the same multiplicative factor, like multiply both by 0.75) until the fastest flight speed you use does not oscillate.  That leaves it a bit slower to respond than it could be when you are flying slowly, but it works.

The best solution is to use an airspeed sensor so the PIDs can be reduced automatically at high speed.  I don't remember whether CC3D supports airspeed sensors, or whether you need a Revo class FC to do that.
Title: Re: Roll oscilating
Post by: DocHardinger on January 26, 2017, 07:02:50 pm
Okay...
But i thought i got only P in Attitude mode? I is set to 0 always...Or am I wrong?
In RateTrainer mode it seems to fly well...
Title: Re: Roll oscilating
Post by: f5soh on January 26, 2017, 07:09:27 pm
Currently airspeed sensor cannot be used to reduce PID.
Airspeed sensor is not supported by CC3D because no analog input or simply no airspeed support.

You can maybe use the TPS function as a alternative, based on raw Throttle.
Flying Attitude you should also take a look at outer loop P gain and reduce a bit.
I term is always 0, see tooltip.

https://librepilot.atlassian.net/wiki/display/LPDOC/Attitude+Setup#AttitudeSetup-Controlstructure

Title: Re: Roll oscilating
Post by: DocHardinger on January 26, 2017, 07:37:43 pm
Ahhh okay...that make sense now...should have take a look at this page earlier ;-)...
Thx Guys