A group of students built this amazing gymnastics robot using LEGO Mindstorms NXT parts and several custom-built joints. Video after the jump.
We used LEGO Mindstroms NXT to build a two-link gymnastic robot which can perform giant loops on a horizontal bar. The hand-and-bar link is a free running passive joint. Two NXT motors are used to drive the robot-shoulder link. We are still seeking the factors to make repeatable and predictable loops