I just recently upgraded my plane from an original 3dr pixhawk to a cube orange. We I go into stab or FBW A or B the Aileron servos and elevator servos with twitch randomly when the plane is sitting on the bench. I get this random twitching if I pick the plane up and roll and pitch the plane.
I thought it was just the gains were to high. However if I lower the gains the twitching is still there but with a lower amplitude.
any ideas guys I may be the guini pig here.
to narrow this down, please do the following:
- test in MANUAL mode, see if it still twitches
- test with GPS not connected
- test with throttle stick above zero position
- test if being armed changes the result
Also, please set LOG_DISARMED=1 and send an onboard log while the twitching is happening
Okay when I state twitching below this is happening on on AL and ELE channels
okay here are the results,
MANUAL mode there is no twitching
When I unplug here GPS twitching seems to stop! Might be a lead here!
throttle above zero with GPS there is still a twitch
vehicle armed there is still a twitch
do you have any recommendations to get the bin file up. Its to big even compressed.
Update: I also just tried with my old 3dr gps and the servo twitching problem comes back.
I think you are on to something because when I unplug the GPS the twitching problem goes away.
This is actually not surprising. The scaling speed will be calculated using GPS velocity, and that effect is maximised at close to zero speed. The effect goes away once you are flying.
Also note that the effect is larger indoors.
I tried flying today and it went well. I did not notice any twiching in flight! Thanks for the help tridge!
@Brian, I have the same problem, and this discussing explains a lot. Assuming you are hand or bungee launching your plane, does your plane wing flutter and than fluttering goes away?
Hey @RizHass I have landing gear so normal take off and landing for me down a runway. What I can tell you is in flight there is no twitching happening. So I think you should be good to go.
I am hand launching a wing so our situation is quite different. Here is a video clip that would explain what I am talking about.
yes it is indeed. I think you are actually seeing an aero elasticity problem. Is that a form board wing?
what mode are you flying in? If you are in manual mode an you see the result in your video then is an aircraft structural problem.
Did you ever try giving full throttle after the flutter stops? I am wondering if the flutter would come back
Its a EPP foam wing made by CrashTest Hobbies (Very tough).
I flew in FBWA mode, and tested RTL as well few times.
Its not a structural problem because after few seconds of flying it settles down and I can fly full throttle with no issues.
Your original topic in regards to twitching servo, explains the behavior one can expect as the GPS starts to report velocity which loops into EKF error with accelerator and creates this phenomena initially.
I will have to AutoTune my plane to reduce gains, since my last AutoTune was done during extremely windy day.
Here is another video of the same flight after fluttering went away. BTW, onboard video is from single-axis gimbal (Roll) mounted camera.
got ya, yea my original post may be your problem then.
Can you try taking off in manual mode? That is how I take off with my plane. If it dose not flutter like crazy then yea I would say its the EKF error.
Have you tried manual tuning? I know it is recommended to do auto tune but I found I could get much better results this way. I used the tuning plots in MP.
At the time of writing this post I had been using Arduplane 3.9.xxx a lot and had not seen my servos twitching when the plane was sitting on the ground.
Great flying site BTW!
Cant thank you enough for this information. Would you happen to know how to manually adjust the scaling that results in these twitches? Also Why is it that the effect is worse indoors? Does it have to do with the quality of the GPS link? because I am getting the same number of Sats indoors as I do outdoors