Inspired by BB-8 from Star Wars, this was my attempt to build an autonomous spherical rolling robot.
Simply, a drive unit with two diametrically opposite motors is freely suspended inside a spherical casing and an obstacle avoidance unit on the outside of the casing is coupled to the internal unit via Neodymium magnets. Two ultrasonic ranging sensors mounted at 45° to the tangent will detect obstacles and communicate to the unit inside via a 433MHz radio.