Algebraic estimation of impact times: Juggling a ball with a magnetically levitated plate

A plate that may freely move in the field of four electromagnets is automatically controlled such as to keep a ping-pong ball bouncing. A simple mathematical model of the process is used together with an algebraic derivative estimator in order to estimate the impact times of the ball. This information is used to predict the next impact. The only measurement used in this process is the plate position measurement. It is related with the reference forces in order to generate a motion appropriate to keep the ball bouncing. Precision and robustness against measurement noise, mechanical vibrations, and fast motions of the plate are achieved by a suitable parameterization of the algebraic derivative estimator and an automatic calibration. Experimental results are shown.