Elihu Thomsonʹs jumping ring in a levitated closed-loop control experiment

A conducting nonmagnetic ring is levitated above a coil excited by an ac source, using the same principle as that of the well-known jumping ring experiment, originally discovered by Elihu Thomson. The ac source is amplitude modulated to ensure that the ring stays in a stationary levitated position. The circuit is analyzed using a simple electrical/magnetic treatment, and the parameters of the system are found. A control strategy is derived for the system, after it has been linearized for small perturbations about an operating point. A simple low-voltage implementation is also shown, with results.