Yes, but it's the math behind those mixer calculators that's pretty flawed, and what I was pointing out above. The relationship ends up being totally non-linear due to the r^2 factor in the moment of inertia calculations (totally ignoring the interaction of the other variables that complicate it even further), and then the mixer is not being applied by the FC in a way that makes the impact as expected. As Boris pointed out, it's actually a hold over from the way some old PID controllers did things that aren't even used anymore. The only real benefit to the mixer right now is making your PIDs more similar, adjusting for vectored thrust (A-Tail or V-Tail) or remapping motor outputs. I'd have to check in more detail to see how they're being applied to the accelerometer, but I don't believe it's really any different. Again, it might be helping but it's mostly blind luck IMO, and the fact that we happen to be in a range where the changes aren't that far off from linear.
Also an important point here, as you hit on, it's the distance of the accelerometer from the CG that seems to matter to level modes, not the distance of the motors from the center of rotation, which is all the custom mixers are accounting for.
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- Unapproved
quadmcfly:
Aug 27, 2016 at 10:10 PM
Yes, but it's the math behind those mixer calculators that's pretty flawed, and what I was pointing out above. The relationship ends up being totally non-linear due to the r^2 factor in the moment of inertia calculations (totally ignoring the interaction of the other variables that complicate it even further), and then the mixer is not being applied by the FC in a way that makes the impact as expected. As Boris pointed out, it's actually a hold over from the way some old PID controllers did things that aren't even used anymore. The only real benefit to the mixer right now is making your PIDs more similar, adjusting for vectored thrust (A-Tail or V-Tail) or remapping motor outputs. I'd have to check in more detail to see how they're being applied to the accelerometer, but I don't believe it's really any different. Again, it might be helping but it's mostly blind luck IMO, and the fact that we happen to be in a range where the changes aren't that far off from linear.
Also an important point here, as you hit on, it's the distance of the accelerometer from the CG that seems to matter to level modes, not the distance of the motors from the center of rotation, which is all the custom mixers are accounting for.