105mm 8520 microquad wobbliness


#1

You may remember the microquad i recovered from a tree after 15 days…:sweat_smile:
Well, i didn’t have the chance to know how it flies until now, and i’m not happy with it. I’m used to a tiny whoop, and this is totally different, of course. I guess the difference lies in the rpm of the motors and the props, so i have to experiment with different props to see if i can turn this “heavy butt” quad into something a little bit more snappy

But one of the things that bothers me the most is the wobbliness in every maneuver. Here i found a good example in this video (not my video):

In my case the wobbliness isn’t so intense. What causes this? Is it a bad pid tuning? How can i tune it right?


#2

Bad PIDs, plus youtube trying to stabilize for him I think.
More P.
My kingkong Q100 build (~38g no battery) with 14.7kv motors, afunta props, and a mpu6000 gyro running 8K gyro 4K PID loop, ended up at 110P 160D.
Raise P till you get small very fast oscillations (as opposed to the large/slow in the video), then raise D till they go away.
No active braking, so high D won’t roast the motors like brushless.

That’s the really, really, very, extremely condensed version of @NotFastEnuf style tuning, which has generally worked great for me.


#3

Great! I’ll give it a try and follow those steps. Thanks!!:grinning:


#4

When you do it, pick a windy day and just cruise around. Nothing dramatic. You’re looking for the point where you have enough P that external forces can’t knock you around anymore. It will oscillate tightly when it gets pushed on … that’s what your looking for. Then raise D till its smooth. You’ll be in triple digits. That’s normal. Set I at 75 across the board to start. If you do this on a gusty day with bumpy air … it will fly awesome in any maneuver you push it into after that.


#5

Coming home after flying some packs with the 8520. I’ve been changing pids and rates on field with the ezgui app (very useful!!). Just followed your advices but didn’t have to raise D a lot. It just flies much better at around P75 and D75, and oscillations are gone.

I think i’m getting the hang of this powerful micro. You just have to correct direction more agressively than i was used to do with my whoop. Anyways i just need a bit more open space to feel really comfortable flying this thing. It takes a lot of speed very fast!

Thanks guys!


#6

Well done! As your skill improves (which it does for all of us with stick time) - you will probably be able to force out some bad behavior on those pids in aggressive maneuvers. So just watch for it doing anything its not supposed to and be ready to move up when need be. But for now - if it feels good - go fly the props off of it!!! :smile:

The more aggressive correction needed is the momentum you’re carrying from having more weight than a whoop. Totally normal. You’re flying a heavier craft.