Modeling and control of magnetically levitated rotating machines

Characteristics of magnetic bearings are inherently nonlinear and unstable due to the nonlinearities of electromagnetic fields. Such properties introduce complexity to the system dynamics and control. To achieve successful operation of such devices in rotating machine applications, this paper addresses critical issues associated with modeling and control. A model refining procedure based on experimental data is discussed. The resultant model not only explains the nonlinear electromechanical coupling but also includes nonideal effects such as flux leakages, fringing fluxes and the eddy current loss. An adaptive control scheme using a local function estimation concept is designed and validated both numerically and experimentally. The tests conducted, for spinning and nonspinning conditions, show that the system exhibits a superior performance