I have never messed with robotics, but I just developed a need to light LED's on a spinning disc. I am going to use the very clever Adafruit Neopixel protocol, so I only need three wires to control even a fairly large number of LED's. Back in the days of DC motors with brushes, getting power to the armature (rotating part) was done with metal contacts resting against spinning copper cylinders. I suppose such commutators still exist for robotics, and I'd like to be pointed toward a good source for them.
Also, any moving mechanical connection is going to generate electrical noise. Any idea how high a data rate I could get through such a commutator?
There are still slip ring type assemblies available but they tend to be somewhat expensive. The easiest solution for just three conductors is to utilize 1/4" stereo phono plug and jack. Use good quality metal types and you should bet decent life out of them and they can pass quite a bit of current if needed.
