New PX4 Frame Type Required to Support Octo H Coaxial Frame?

1

Hi all, I’ve build a Octarotor H Coaxial frame and since no such airframe setup currently exists in PX4 I’ve used the Octorotor Coaxial setup. I did have my concerns over the pivot point to control this but got as far as a test flight today and confirmed my fears.

In Stabilize mode (default PIDs) just after I take off the aircraft starts a slow oscillation the toilet bowl movement (sometimes seen in POS with a bad calibration). Video here

I’ve not got as far as trying to decifer the PX4 code base but before I do can any PX4 devs confirm the pivot point on an H vs X frame is the issue why this will not work?

Or is what I’m seeing the result of a bad initial PID tune?

Given the time and cost of the setup I have zero tolerance for a crash! Hence the brief low hover.

The H axis is roughtly 700mm between motors left and right and 1m diagonally.

Many thanks

David

2

It seems like creating a TOML file with the geometry may be required as discussed here.

3

Hi David,
I am also making H frame Quad Co-axial multicopter and faced the vibrations issues on Ardupilot when i have set the “H” frame on Airframe selection. Then I have moved to PX4 and it has two airframe config. namely: Octo Coaxial Wide and Octorotor coaxial. I was wondering how your flight tests went and which airframe you have selected. Also what is your prop size.
Aman