Re:The Rubik's Contraption
by amluto on Saturday March 10, 2018 @11:08PM
(#16561654)
You’re assuming they’re using a linear controller, and they’re way ahead of you [1].
But I don’t think they’re overshooting per se. I think they’re landing the centers in the right place, but the outer pieces account for most of the moment of inertia, and they’re flexible, so the overall assembly is deforming. Deriving the optimal control law for that could be a bit messy. I would guess that it involves bringing the center piece nearly to a stop slightly short of 90 degrees and then gently bringing it the rest of the way.
Re:The Rubik's Contraption
by Klathmon on Sunday March 11, 2018 @09:34AM
(#16562908)
They talked about how "mistakes" in the tuning often resulted in exploding cubes. I have a feeling they probably tried that or something like it but it just puts too much stress on the cube.
But I don’t think they’re overshooting per se. I think they’re landing the centers in the right place, but the outer pieces account for most of the moment of inertia, and they’re flexible, so the overall assembly is deforming. Deriving the optimal control law for that could be a bit messy. I would guess that it involves bringing the center piece nearly to a stop slightly short of 90 degrees and then gently bringing it the rest of the way.
[1] https://build-its-inprogress.blogspot.com/2017/12/controls-r...