[EricH]

It's kind of hard to drive a robot on concert--the musicians hate having it run over their instruments.

Most robots are just fine running on concrete and asphalt as well as carpet. The main problem you might have is with the omni wheels. If they're in pairs with the rollers offset, you should be OK.

If you're concerned about the rubber wheels, get some conveyor belting and attach with screws. That'll add an extra layer of protection to them. For the omnis, if you're concerned there, that's where you use just rubber wheels that have been thrashed around for a season or more--you don't exactly care if they get chewed up by the rougher surface.