> Using cameras just overcomplicates things for worse results.
If you use a crude algorithm, maybe. But given what's possible with photogrammetry, I think you can use that as another sensor fusion input, with a kalman filter or something similar, and get even more precision at the output.
That's way more complicated when it comes to the algorithm, of course. But the idea was being able to plug more sensors and improve precision.
It uses brushless motors and encoders.