Fixed Wing PID windup issue going into Attitude, RTB, etc.
« on: June 15, 2017, 07:12:28 pm »
There is an issue in 1609 fixed wing stabilization.  When flying Manual the stabilization PIDs wind up so that when you switch to a stabilized mode it can go very bad for a couple seconds while the PIDs unwind.  This is mainly a problem for switching into Attitude mode.

This is especially bad for flying Manual and expecting RTB to work without crashing, since RTB uses Attitude stabilization.

Several work arounds:
- (experts) if you are just testing near by, you can man handle it by manually correcting for a couple seconds when you switch from Manual to Attitude.  Just expect a problem and be ready for it.  I have to hold full up and left.  Not for beginners...
- (beginners) if you are just testing near by, you can zero the throttle, then switch to Attitude mode then run the throttle back up.  Zero throttle instantly unwinds the PIDs.
- if you might be flying far away, fly in Attitude mode so the PIDs won't wind up, so that when RTB engages it doesn't go crazy.  Do the switch from Manual to Attitude close by to get it handled before flying farther out.

This would be a simple fix to have Manual mode constantly zero the windup.

I've been living with this for a while, but I see that some people (@jdl?) may be having this issue, and I thought I would post about it.