Electromagnetic(EML) or attracting levitation can levitate the suspend mass by means of the attracting force created by the electromagnets,which are inherently unstable if the currents are constant.Therefore feedback forces are required to stabilize EML devices.There are several EML methods that may be classified as direct,position feedback-control techniques and ac modulated or indirect feedback methods.In order to obtain stable levitation,the nature of the magnetic force should be a restoring force.After analyzing the magnetic forces,the statically stable condition can be obtained directly by means of the magnetic stiffness conept.In the direct position feedback-control EML,for a necessary condition for stability the control stiffness should exceed