Last time I tried to make a robot which balanced on one actively-driven two-axis omni-wheel. This wheel is driven by two motors in a differential drive configuration so it can drive sideways as well as forwards and backwards like a normal wheel. The design was mostly taken from a Honda Patent and Honda had showcased a proof-of-concept machine called the U3-X. The original design showed all the wheels around the circumference being driven together by a flexible shaft, but this is very hard to rep