Greeting all,

When I push the rudder, I can saw my quad will wobble.

I believe this is due to low KV motor.

I already try tune Stabilize KP and Yaw Rate KP. But result is same.

I put 'Angular Rate Control'  P = 0.090 

Below are my setting:Motor: NX-4006-530kv
ESC: Multistar 30A
Battery: Nano tech 4S, 4000mah (if use 3S, quad will be not stable and will lost control)
FC: APM 2.5 (2.9 firmware)

Below my quad video:

https://www.youtube.com/watch?v=2kFpEHuLzpg

Please somebody advise me the best PID setting??

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Replies to This Discussion

try decrease yaw angular rate P  by 20%

im use 0.12 at quaid with 14 inch props

The copter also wobbled during forward flight and during fast down.  That tells me that the Rate Roll and Pitch PIDs need tuning (Config, Standard Parms, Arducopter Config) first and then do Yaw.  Make sure that the rate roll/pitch D value is large enough (just under fast oscillation).  Then tune P and then tune I.  Good pitch and roll PID tuning will help yaw be stable.

You should be able to lose altitude quickly without wobbling.  If it does, the roll and pitch PIDs are not tuned well enough.  Tune in acro not stablilize mode.  Build a good 1 dimensional test stand (that only allows pitch) to do this:

  • put a long bar through your copter frame.
  • secure the copter to the bar in a way that your copter will rotate around the bar in pitch (fore and aft).
  • balance the bar on two posts on either side of the copter.
  • allow the bar to rotate on the posts but not come off the post.
  • hand hold the copter above the bar
  • start the copter and let it get stable
  • let go
  • apply a little pitch
  • study the response and wobble
  • return to neutral and study the response and wobble
  • try at different throttles (but don't over heat)
  • accordingly adjust rate pitch/roll PIDs per the instructions via Mission Planner USB or telemetry link
  • with that complete find a camera tripod with a camera ball socket
  • mount the copter to the ball socket
  • hold the copter during power up and get it stable
  • apply yaw and study the response and wobble
  • adjust rate yaw PIDs
  • too much yaw might overpower the pitch/roll PIDs
  • good luck and share your findings

 On the fast descent in RTL, there is a parameter for changing the speed of descent.

Thanks Kozin. I will try to tune pitch and roll first as mention by Frantz.

Frantz, thanks for the advise.

It a bit hard for me to make test jig.

Anyway I will try to tune this weekend on the field as you propose.

Thanks a lot..

take a brook stick and duct tape it to your copter if needed and place the broom over two chairs with the sweep side free to rotate ... that becomes your fulcrum.

I done roll and pitch PID tuning. I tune by holding quad using my hand.

After that I make field test.

I found my quad more stable then before. But wobbling still happen when I input the yaw.

Next I will try yaw rate PID tuning and update you all later.

Kozin, what type of motor you are using?

Did you figure this out.. i'm also struggling with wobble on my quad when i yaw..
I have tried a few different motor/frame setup's but they all have the wobble when yawing to some degree..

I have exactly the same problem. I managed to tune the roll and pitch P values so the copter flies reasonably well in stabilized mode. In loiter mode however any yaw command immediately disturbs the stability. The copter wobbles precariously while circling the loiter position and climbing in a cork-screw fashion. As soon as I let go of the yaw command the copter stabilizes nicely, moves back to the original loiter position and stops climbing. Also, when I attempt to fly horizontally in any direction, the copter gradually looses altitude. When I let go of the stick, it stops gently and recovers to original altitude.

I am using 400KV motors with 13x4.7 props and 5A ESCs on 32.5cm long arms, 5s, take-off weight approx. 3.2kg.

Any hints on further tuning will be appreciated.

Nano & Svein - 

My guess then is balance.  If the copter is not balanced, as you rotate, the copter rotates around the mass, not the center of the copter.  This in effect changes your square motor layout to a spider layout that has coupling between yaw and pitch or yaw and roll.  Spiders handle this via changes in the software.

Find a way to mark the center of your craft on top or bottom.  If on top, attach a string to that CG point.  Lift the copter up by the string.  It shouldn't quickly tilt to one side.  If on bottom, balance the copter on a rod or your finger.  Move the location of the battery until the balance is good.

I'm assuming at this point that:

o your props are all the same.

o your motors are all the same.

o the motor layout is a perfect rectangle or square

o you have turned the yaw PIDs down and that still doesn't help

Walter - Also check the balance (see above) of the ship and report back.

I've been told that sun impacts altitude hold so I assume you have blackened the APM.

Forrest,

The balance issue makes a lot of sense to me. I'll test it and get back to you.

Thanks for responding.

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