HIGH-PRECISION MAGNETIC-LEVITATION DEVICE WITH ELECTROOPTICAL FEEDBACK

We report on a magnetic levitation device with electro-optical feedbac k which allows for precise stabilization of the vertical position of t he levitated piece (LP) within 1 mu m. The vertical position of the LP is monitored through the reflection of a laser beam on a mirror place d in the upper part of the LP. The reflected beam goes to a position s ensitive photodiode and suitable electronics transforms the fluctuatio ns in the vertical position of the LP to an electrical signal. This si gnal is fed into a PID controller that drives an electromagnet. The ou tput of the detection stage yields high-precision measurements of the fluctuations in the vertical position of the device and the current fe d to the electromagnet provides a precise reading of the vertical forc e felt by the levitating part. We have also developed a model that exp lains most of the dynamical behavior observed. We have formulated the dynamical equations of the system and, by means of a linear perturbati on technique, we have obtained the stability characteristics which com pare well with the experimental response. (C) 1995 American Institute of Physics.