Double inverted pendulum

A double inverted pendulum is like a regular inverted pendulum, except that it is made up of two stacked pendulums. The top pendulum has a large mass and a long arm, while the bottom pendulum has a small mass and a short arm. These two pendulums are connected by a motor, and the goal is to keep the pendulums balanced, with the top pendulum upright, and the bottom pendulum sideways. To do this, the motor adjusts the speed of the bottom pendulum so that gravity does not pull it down. This is a difficult balancing act and takes a lot of practice!