This video, created in 2026, is a 2-link Futura-style underactuated mechanism whose base axis is driven by a single Puck® brushless servomotor controller. The second, unactuated joint, has an encoder only — no motor. There is a weight at the end of the outer (2nd) link.

There are two phases of control. In the first swing-up phase, an energy technique is used. Once the outer link is within 20-degrees of vertical, the 2nd phase kicks in to maintain balance. Due to the low-friction joints, precision control, and high bandwidth, it merely uses linearized PID control to maintain balance.

The specific Puck® used is the 2-gram, 400W P4-16™ variant, which you can see in the video at the top of the base.