This mobile robot has just two moving parts - AI Trends

The only other active moving part of the robot is the body itself. The spherical induction motor (SIM) invented by Hollis, a research professor in Carnegie Mellon University's Robotics Institute, and Masaaki Kumagai, a professor of engineering at Tohoku Gakuin University in Tagajo, Japan, eliminates the mechanical drive systems that each used on previous ballbots. Because of this extreme mechanical simplicity, SIMbot requires less routine maintenance and is less likely to suffer mechanical failures. The new motor can move the ball in any direction using only electronic controls. These movements keep SIMbot's body balanced atop the ball.