Hi, I have made a huge coaxial drone now.
I have now uploaded the Copter-3.5 firmware to Pixhawk.
The Frame Class is set to 9 (coaxial).
Over the past six months, wobbling has been consistently demonstrated in the Tethered Hover Test.
Now the problem is solved.
The cause was the 90 ° phase angle, which is the basic principle of the helicopter.
I turned all the equipment including Pixhawk counterclockwise 55 degrees.
I think this problem is very interesting and needs to be understood.
I would like to upload videos, but I will post the video later because it is one of the national projects.