Hmm... i just had a hover-maiden. AUW is at the moment 240g, yet without the Caddx Vista. So i need to shed another 10g to stay under 250g in the end.

However! Using stock Betaflight settings, after launching it started gentle wobbling itself higher and higher, even after i reduced the throttle to the lowest setting. Had to cut the throttle completely for a controlled crash.

Does anyone have experience tuning such a weird drone? ^^ Probably i need to reduce the PIDs to a minimum and start from there. And deactivate all the extra filtering options (DMIN and such).

Hi Felias,

The.ronin is one of the best at PID tuning. He also has a couple of Tutorials; will see if I can find them.

(07-May-2021, 04:01 PM)Felias Wrote: Hmm... i just had a hover-maiden. AUW is at the moment 240g, yet without the Caddx Vista. So i need to shed another 10g to stay under 250g in the end.

However! Using stock Betaflight settings, after launching it started gentle wobbling itself higher and higher, even after i reduced the throttle to the lowest setting. Had to cut the throttle completely for a controlled crash.

Does anyone have experience tuning such a weird drone? ^^ Probably i need to reduce the PIDs to a minimum and start from there. And deactivate all the extra filtering options (DMIN and such).

My 2s li-ion quad had a small "wobble", although turning "vbat pid compensation" fix almost all the "wobbly flight control", also your pids will be much easier to tune.

(07-May-2021, 08:56 PM)Joshua_A Wrote: My 2s li-ion quad had a small "wobble", although turning "vbat pid compensation" fix almost all the "wobbly flight control", also your pids will be much easier to tune.

Oh! Never heard of vbat pid compensation. Is it turned off by standard? But will try it out for sure! You think i can go with stock settings otherwise?

Edit: hmmm... it seems this is more relevant for when the voltage drops lower? How will this influence the PIDs when the battery is full?

(07-May-2021, 10:17 PM)Felias Wrote: Oh! Never heard of vbat pid compensation. Is it turned off by standard? But will try it out for sure! You think i can go with stock settings otherwise?

Edit: hmmm... it seems this is more relevant for when the voltage drops lower? How will this influence the PIDs when the battery is full?

Firstly,  yes vbat pid compensation is off by default.

Secondly, It looks like you WILL need to tune your pids...
but having it on won't affect your tune at full battery, just adjust with the voltage drop (which is quite large when running 2s li-ion... ).

So to be more clear: When I tune a 2s li-ion quad, I turn vbat pid compensation on first (this almost alway fixes that crazy "low battery wobble"), then I tune, because your turn will be off at the end of your pack without it...

EDIT: But there have been times that the vbat pid compensation fixed the "full battery wobble" also... I'd give it a try either way.

Thanks a lot, this is helpful

I‘m not really sure if i should start by deactivating everything and turning PID-values to the bare minimum and start from there - or just turn the sliders all to the left and start from there instead. Was hoping i could find some experience from others with a similar quad - but couldn‘t find anything sadly.

Remember the Vid i sent ou when i had exactly the same problems with my 8"?


P*2, I*0.6, D*0,5 from the Betaflight defaults seemed a good start.

(08-May-2021, 08:13 AM)derFrickler Wrote: Remember the Vid i sent ou when i had exactly the same problems with my 8"?


P*2, I*0.6, D*0,5 from the Betaflight defaults seemed a good start.

Thanks! I tried these numbers, but sadly it still shoots up uncontrollably.

Then i switched off all filters, and set P to 20 on all 3 channels, and D to Zero on all 2 channels. Then it was hovering perfectly! I upped P until 65 - if i went higher it oscillated too rapidly.

Then the interesting thing happened: As soon as i add D at a value of 10 or higher, it shoots into the air again. At 10 it does frequent throttle boosts, at 20 it just pushed throttle without me doing anything.

So i need to better understand what D does, and why it is causing this behavior. It might be in the end that the frame just isn't stiff enough and protected against torsion - who know. But i'll try to figure it out before i give up :-)

I'd look at your noise plots first. D-gain can cause real problems in noisy systems.

But I'm waiting for Ronin to come and correct me ;-)

#1. Dont try to fly until you have blackbox logs showing you 100% solved it. Dont rely on "it looks better".

PID on big quad is so different because its like ballerina/skater with weights on stretched out arms - takes a lot of power to get going and to stop. Lots of momentum.

D is supposed to dampen exactly like shock in car. It uses derivative = slope of the gyro.

Gyro moving fast = dampen more.

Except it cant distinguish fast shaking, which it tries to correct, but actually overcorrects and causes even more shaking.

This is why big quad needs very stiff (6mm+) arms, stiff propeller, and probably better without soft mounting FC. High frequency noise can be filtered, but lower frequency cannot.

(06-May-2021, 11:04 AM)hugnosed_bat Wrote: how to balance a such a foldable rotor?

Balancing seems totally overrated.
Flew over 1min with this guy after hitting a metal structure. Had to punch-out to recover it after the hit and it felt sloppy and was missing power.
After landing ~1min later i saw the props ;-) Incredible what the controller can take nowadays...

   

Hi Der Frickler,

I tend to agree with you on prop balancing. I just don't see it making a difference on quads 5 inches or less. I have run a variety of props on a quad and can't tell the difference. I have even drilled out the center hole from 1.5mm to 2mm with a DeWalt drill {and not very precise either...no two are exactly the same} and the props work fine and the quad is stable.

Now, when you get up to 7 inch and greater and are running heavy, maybe carbon fiber, props; it starts to be more important.

Sure, the bigger the props, the more it matters, did it aswell on my 15th" and 17" quads but from my experience below 10" it does not make much difference.

(07-May-2021, 04:27 PM)iFly4rotors Wrote: Hi Felias,

The.ronin is one of the best at PID tuning. He also has a couple of Tutorials; will see if I can find them.

That sounds great! How can i get a hold of him?

@The.ronin requested! I have a superlight drone (240g AUW) with large propellers (7“) compared to the motor (2004 2100kv), using a 2s Li-Ion-setup. When my D-number is higher than around 5, the throttle just keeps going uncontrollably. Help needed! :-)

(13-May-2021, 08:33 AM)Felias Wrote: That sounds great! How can i get a hold of him?

@The.ronin requested! I have a superlight drone (240g AUW) with large propellers (7“) compared to the motor (2004 2100kv), using a 2s Li-Ion-setup. When my D-number is higher than around 5, the throttle just keeps going uncontrollably. Help needed! :-)

Send him a Private Message (PM).  Here is the.ronin's Blackbox Tuning guide.  <- From his new website RoninUAV

I can't seem to find the PID tuning guide that he did. It is very good. I will keep looking. >> See the Next Post <<

Also, voodoo has a PID Cheatsheet <- Click Link

Another PID tuning guide >> Understand PID Tuning in 2 minutes or less...