I am working on making a SLAM (simultaneous localization and mapping) robot using the NXT, and one of the things I would like for it to have a "Fifth-Wheel Tachometer", i.e. an independent, un-powered wheel who's sole job is to measure distance. I was hoping that a fifth wheel design would be more reliable, as not only would the fifth wheel never move if the robot wasn't, but I was hoping that it might slip up differently from the powered wheels, allowing for a more precise measurement via cross comparison.
The trouble is, I can't get my third NXT motor to "coast" and let the fifth wheel turn freely. Is there a way to get it to do this, or do I need to use some other sensor for the fifth wheel (if so, which do you suggest)?
"The name's Jond, Bames Jond..."