robotic ball balancing beam
The Robotic Ball Balancing Beam is a standard feedback control project. Normally a ball will not naturally balance on a flat beam unless it is perfectly balanced; it is an unstable system. A feedback control system must be designed in order to stabilize the system, especially if you want to move the ball to specific positions along the beam.
In this case, an inner and outer loop control system were developed - a potentiometer to feedback the angle of the beam, and a linear resistance sensor to measure the ball's position along the beam. Combining the two with a lead compensator, the ball is not only stabilized but can be commanded to arbitrary positions and patterns along the beam.