[Alan Anderson]

KatsKlaw (team 45's 2004 robot) used Banner sensors pointed at black stripes on the wheel hubs. For initial testing, we had six evenly spaced pieces of electrical tape, alternating with nicely reflective aluminum. The RC had no problem keeping up with the relatively slow signal and its correspondingly coarse resolution. The resolution ended up being just under three inches of linear travel on the field, or about ten degrees of turning in place. That turned out to be plenty for what we needed, so we never tried making it more precise with additional stripes.

For something like closed-loop speed control, more precision is desired. We intend to play around with prototype drive bases for the next couple of months, and rotary shaft encoders might be an option. From what I've seen, building one with optical sensors and a slotted disk is probably going to end up being cheaper than buying one.