I’m in the process of designing a heavy lift drone. The target is to be able to lift up to 50kg. I’m starting with a smaller version to lift 15 kg, MTOW around 45 kg.
It is an octoquad design, dimensions 1.5m wide and 1.9m long. Empty weight will be around 25kg.
I’m not sure if the standard PID values will be a good starting point and I look for some help.
Thanks in advance.
Read the entire wiki. It provides information on how to tune big frames.
THEN, use mission planner, ALT+A and generate your default parameters based on copter propulsion data
Thanks a lot. I didn’t know this existed. Very useful answer.
What prop size will be used on each of these? The MP Plug get’s a bit wonky with the filter values >24"
I intend to use 24 motors, prop size 15 x 5.5
Then the values produced from the Plug-in should be a good starting place.
Dave, any recommendations for props larger than 24’’ ? I used with several 32’’ copters and tune was quite good.
Hi Andras-For 32" props the Plug-in suggests Rate filter values of 8Hz and in some recent cases this has been too low. Raising this to ~11Hz has fixed some tuning problems. What is your experience with this? Also, note that the ATC_ACCEL_P/R_MAX values go to zero ~38" prop. So my suggestion is the Plug-in functions probably need some tweaking in this regard.
Well, the idea is to use an octo-quad configuration where on every end 3 props spin in the same direction, as if it is 1 big prop. So on the left top, 3 spin CCW, down 3 spin CW. So together. And the same for the other sides.
In my idea, these will act as big props of around 30".
Will the value of the plug in still be usable?
I don’t understand what your are describing. If it’s not a Motor Mix in Arducopter you will have to come up with the Mixer.
For octoquad (X8) or coaxial configurations use the actual prop size in the calculations, for example 15" and NOT 2x15=30" on each arm.
I do have quite some experience with Ardupilot and a lot of the wiki is just basic information. Would take a lot of time to read the entire wiki. Could you indicate which section provides information on how to tune big frames?
Is this what you mean?
How do get 24 motors on an Octoquad?
I suck at drawing but he may be doing the following… I think.
Each arm has 6 motors - 3 on top and 3 on bottom.
Yes, its like that, but instead of inline, the motors are as a triangle.
So you are coding your own Motor Mixer?
No motor mixer. The upper 3 all turn in the same direction. Like 1 big motor. Just in parallel. Same for the lower 3.
No idea if this works. Just proof of concept and start with a small version.
You want to keep in mind that smaller props are less efficient than big props, and you’ve got a lot of additional weight and complexity overheads.
For example, an Octocpter has good redundancy but has to use small(ish) props or they wont all physically fit together without overlapping, or the frame has to be incredibly large!
A regular quad is much more efficient because it can use larger props and there’s less overheads (weight, complexity) but has no redundancy.
An Octoquad (X8) is somewhere in between - large props are possible and there’s redundancy. There’s still some extra weight and complexity, but hopefully it’s outweighed by the better props.
You’ll notice a lot of commercial heavy lift multirotors are Octoquads, although it depends a lot on the exact requirements.