Octo H Frame Motor Mixing

Moving the topic out of Copter-3.5 Testing List as this is diverging from topic.

First off here is an image of the aircraft we fly, in case I am wrong but I believe this is called an H8 or Octo H

We have been flying them with Octa firmware Frame = H. Please correctly me if this is incorrect.
Also the motors are setup the same as Octa as we discussed on the forum a year or so ago.
Now Randy has confused me saying “I think the difference between an X and an H is just the direction of the propellers”
My understanding, again correct me if I am wrong, the main difference is the motor mixing.
As the inner motors, are 50 %closer to COG than the outer motors. Therefor they need 50% less rpm to rotate the aircraft on pitch to the same radius as the outer motors. I actually thought this was the other way around as I am thinking of leverage but I was corrected of this on the DIYDrone forum some time ago. Making the motor mix look something like this:- Note this is from Clean Flight, I never actually found the syntax for Arducopter
mmix 1 1 -0.912 -1 -1
mmix 2 1 0.912 1 -1
mmix 3 1 -0.912 -0.333 1
mmix 4 1 -0.912 1 1
mmix 5 1 0.912 -1 1
mmix 6 1 0.912 0.333 1
mmix 7 1 0.912 -0.333 -1
mmix 8 1 -0.912 0.333 -1

Or have I completely got this wrong?

Ok, interesting, that’s why I asked what was different, I wasn’t seeing why it would be so different in an octa between an X and H frame. This makes more sense.

@rmackay9 comments on this? This does look more like an H than an X with propellers in inverse direction.

Ok, so this frame requires a new motor mix and it probably makes sense to call it “H”.

After a chat with Leonard I’ve removed the Hexa-H and updated the Octa-H roll, pitch and yaw factors to what Leonard suggests they should be. https://github.com/ArduPilot/ardupilot/commit/8b5aae37e0fd4649453f82d60554f850cc3dc554

I’m a little concerned that we’ve made a mistake with the factors so I was wondering if @ACPUK could perhaps load up “latest” some time soon (but wait at least 5 hours from the time of this post) and check that it seems ok? You can load up “latest” by going to the Mission Planner’s install firmware screen and press “Ctrl-Q”. You should see the version change to 3.5-dev. Please be careful of course it’s very possible we have some factors wrong so it might try to flip over immediately upon takeoff. If it seems ok this will go out with AC3.5-rc2.

Randy, Oxinarf, Thank you so much, it is 02:30 here in the UK but I will do this 1st thing in the morning and take it out for a test.
Don’t worry I have plenty spare rigs of this construction for crash testing.
In the long term I have a rather large version with 30" blades which is under developemnt at the moment.

common question about mixing. Here is good calc for CF/BF/MW
for example zmr250 mixer is
motor[0] = PIDMIX(-1,0.772,-1);
motor[1] = PIDMIX(-1,-0.772,1);
motor[2] = PIDMIX(1,0.772,1);
motor[3] = PIDMIX(1,-0.772,-1);
mmix 0 1 -1 0.772 -1
mmix 1 1 -1 -0.772 1
mmix 2 1 1 0.772 1
mmix 3 1 1 -0.772 -1

what values should i place in code?
i read rmackay9 post and try understand how it work, but not have complete understanding.
i see 0.333 in code https://github.com/ArduPilot/ardupilot/commit/8b5aae37e0fd4649453f82d60554f850cc3dc554 and can compare with mmix calc data from first post. But i not see 0.912 from calc data in code. This data rounded to 1?

So far so good, not done any tuning but much more locked in now. The ‘seesaw’ effect we had has gone.
I will do a full field test soon.
The rig even sounds much nicer now.
thank you very much.

Ok great. This will go out with AC3.5-rc2. I’m in australia this week at the ardupilot developer un-conference (amongst other things) but I hope to push out -rc2 next week.

Hi Randy, we have had terrible weather here so no more testing has been done.

Motor testing is all ‘greyed’ out, not sure if this a firmware or a Mission Planner thing.

Do you need to separately install Octo H Frame for the Mission planner because I am building one and I just don’t see the H8 Frame
Please recommend action.!!!

Use latest Copter
To setup an H8 go to full parameters and set: -
FRAME_TYPE = 3 (for H)
FRAME_CLASS = 3 (for Octa)