February 16, 2015, 12:46am
During Auto take off, especially on a windy day, my plane has some serious pitch oscillations.
It will climb but the entire time it pitches up and down very hard and the elevons are just going up and down in large swoops the entire time.
It is like one of the control loops of the PID is wayyy to high, however, once it gets to altitude it stabilizes out and flies perfect.
Any idea’s why it would only have these crazy oscillations on auto take off?
Post your pitch PID’s here, but also check for small amounts of slop in the elevator pushrod and connections. Are you launching under full power? What plane?
February 16, 2015, 10:56am
The most likely explanation is that your pitch P gain is too low. In normal flight the I gain will tend to even up the flight, so it will seem to be OK, but during takeoff things are a lot more dynamic and it can oscillate.
If you haven’t run AUTOTUNE yet then please do so.
Also, when asking why a particular behavior happens, please post a log file. Otherwise I’m just guessing the answer.
February 16, 2015, 2:47pm
Thanks for the replies,
Current Pitch P gain is set to .783
Pitch I: .071
Pitch D: .059
Plane is a FX-61 Phantom with stock motor and full MG digital servos (Although APM Plane only supports analog output so it is only 50hz cycle rate)
I will attach the log file somewhere and post it, it’s just over the 2mb limit to upload here directly.
February 16, 2015, 5:21pm
I used someone else’s files when I set it up as he had put a lot of work into tuning the PID’s, however, for my setup I think I have to tune my own.
I flew in acro mode today to see how it handled, and it was terrible. It was flying better in manual mode than in acro mode. I think the PID’s are off.
Next time I get a calm day I will go and use the auto tune and tune from there.
I am also waiting for a cable to hook up my 3DR radio’s so I can tune while in the air.