One of the challenges with humanoid robots, besides keeping them upright, is finding compact combinations of actuators and joint mechanisms that allow for good range of smooth motion while still having good strength. To achieve that researchers from the IRIM Lab at Korea University of Technology and Education developed the LIMS2-AMBIDEX robotic humanoid upper body that uses a combination of brushless motors, pulleys and some very interesting joint mechanisms. (Video, embedded below.)
From shoulder to fingers, each arm has seven degrees of freedom which allows the robot to achieve some spectacularly smooth and realistic upper body motion. Except for the wrist rotation actuator, all the actuators are housed in the shoulders, and motion is transferred to the required joint through an array of cables and pulleys. This keeps the arm light and its inertia low, allowing the arms to move rapidly without breaking anything or toppling the entire robot.
The wrist and elbow mechanisms are especially interesting. The wrist emulates rolling contact between two spheres with only revolute joints. It also allows a drive shaft to pass down the centre of the mechanism and transfer rotating motion from one end to the other. The elbow is a rolling double jointed affair that allows true 180 degrees of rotation.
We have no idea why this took two years to end up in our YouTube feed, but we’re sure glad it finally did. Check out some of the demo videos after the break.