Here is a link to a video of a self-balencing unicycle. I'm curious as to how this works. In particular:
What provides the torque to keep the rider from falling over? I know it's somehow provided by the motor, but this isn't an external torque (if we define the unicycle as our system), and I assume we need an external torque to change the angular momentum of the unicycle.
If you were to try to ride this thing on ice, I assume that it could not prevent the rider from falling over. Is this correct?
What would the free body diagrams look like for this unicycle when it is in the act of falling over? When it is righting itself?