X8 Wookong M gain problem

[Revoflite]

Hi.

Here is my new multirotor setup with Wookong M autopilot and camera gimbal/payload.

For a test filght i have been using a landing gear with dummy weight payload(AUW 8kg) and it has been behaving perfectly and smooth with basic gain at 150 or even over 200(yaw and vertical at 130) without any oscilation.

With the shown gimbal/camera payload(AUW 10kg) which is mounted on a vibratopn isolators lower than dummy payload i'm getting small oscilation even at 30! basic gain and 70 for yaw/vertical. At 100 basic gain it oscilates lake crazy. At this low settings there is really not a lot of stabilization.

I'm using KDE4215XF-465 motors with tri-blade folding DJI 1552 props and Hobbywing Xrotor 50A ESC.
All propellers are balanced.

Do you have any idea what is causing this problem?

Could this be because of soft DJI 1552 plastic blades? If so why am i not seeing any problems with 2kg less AUW? Has anyone experienced any dramatic gain changes after switching from CF to soft plastic propellers like these foldable ones?

 

[eskil23]

Do you get the same Center of Mass with the gimbal as with the dummy weight? I think you can get oscilations if you CoM is too far away from your FC in the horizontal plane.

 

[Revoflite]

No, the center of mass is lower with the gimbal plus increased weight by 2kg but i have applied new settings for CoG to IMU accordingly.

 

[eskil23]

No, the center of mass is lower with the gimbal plus increased weight by 2kg but i have applied new settings for CoG to IMU accordingly.

If the CoG is lower it is still the same in the horizontal plane, it just moved along the vertical axis. A lower CoG should give a more stable aircraft, but if you have not adjusted your gains, it could be overstabilized.

 

[Carapau]

Not sure its the props. How stiff is the frame- very hard to tell from the pictures but I reckon you are close to a 5kg payload which could be causing the frame to flex too much? Really hard to say without seeing the machine in person.

Where abouts is the IMU as I cant see from the pics?

 

[Revoflite]

So far i have tried changing the payload dampers from ultra soft to stiff, different IMU to CoG location settings(Z and X axis) and medium/high ESC timings.
There has been no change in behaviour, still gain related oscilations/wobble visible...

The frame without battery is 3,4kg. Batteries are 2,3kg and the payload(gimbal/camera) is 4,65kg
It is very rigid, everything is secured and tightened up, this is not my first heavy-lift multirotor platform.

 

[Revoflite]

I have also tried wooden Xoar 15x5 props, still the same.

 

[Lanzar]

I will say the frame cant handle it and gimbal is oscilating. Please connect the gimball without rubers and try. I bet this will help a lot.

 

[Revoflite]

I have attached a short video:

You can clearly hear the motor oscilations and see the arms moving up and down(especially the front arms) and camera gimbal wobbling. This was with pich/roll 60 and yaw/vertical 70 basic gain. Attitude gains were at 55.

I have already tried:
-recalibrating compass
-recalibrating each ESC
-firmware reinstall
-wooden xoar 15x5 propellers
-harder and softer camera gimbal dampers(even completely tightened up with zip ties)
-different motor timings
-different IMU/GPS positions(Z and X axis) in configurator

 

[Carapau]

I think it is the frame that is not up to it. What frame is it and are there any specs for it? The addition of a further 4lbs / 2kgs is a 25% rise over the test weight you flew, this would easily be enough of an increase to take the frame from being suitable to unsuitable hence why it flew nicely at 8kg AUW.

 

[Revoflite]

This is a custom foldable frame made from 2mm CF plates. Very rigid, if i hold 2 opposite arms and pu a lot of force to flex 2 others there is barely any give at all.
I have designed a similar platform before that just like this one was super lighweight and carried RED beautifully.
https://www.facebook.com/Revoflite/...152644491536030/469536956513447/?l=51c645f2be
https://www.facebook.com/Revoflite/...152644491536030/465673723566437/?l=20bfc032e5

I'm going to screw the gimbal directly to the frame tomorrow and see how it goes.

 

[Lanzar]

2mm is not even close to enough, And your center plates are too small. Plus additional problems I see that makes this build gonna give you a headache.
I suggest you start from scratch and redo the whole system.