Abstract: Two nonlinear and coupled models governing the electrostatic forces are described for a class of electrostatic bearings with a bias voltage in each electrode, followed by comparison of the derived force models with their numeric integration results. It is shown that the force model expressed by power series of the rotor displacements is accurate only for small motion range while the approximate model is applicable for initial levitation of the bearing with large range of the rotor motion. The necessary conditions for the initial levitation are also discussed to achieve a stable levitation of the rotor inside the electrode cavity in an arbitrary orientation. The simulation results for a three-axis suspended system in various orientations are presented based on the approximated force model.

Key words: Coupled nonlinearities, Electrostatic bearing, Electrostatic force, Initial levitation