Typically the 3 omni-directional wheels makes direct contact with the ground. Even then, holes and obstacles are a concern.
I didn't read the article, but judging by the video I see this more as a proof of concept. The balancing doesn't so much impress me. I liked what I saw of them being used together. If you scale the design up by any amount and increase the friction/traction between the omni-directional wheels and the ball (possibly by using a hard rubber surface that has some give to it) you would have a hard time finding a more capable form of omni-directional locomotion.
I didn't read the article, but judging by the video I see this more as a proof of concept. The balancing doesn't so much impress me. I liked what I saw of them being used together. If you scale the design up by any amount and increase the friction/traction between the omni-directional wheels and the ball (possibly by using a hard rubber surface that has some give to it) you would have a hard time finding a more capable form of omni-directional locomotion.