Active Magnetic Bearing (AMB) is a kind of novel high performance bearingwhich can suspend the rotor by magnetic force. Because of its contact-free mannerbetween the rotor and stator, the rotor can rotate at a very high speed and it has longerlifetime, lower power loss, lower noise, almost no wear and needs no lubrication. Inaddition, it can improve rotor dynamic behavior via feedback control. MagneticBearing has great advantages over the conventional bearings in the application.The hardware and software of the digital controller for Active Magnetic Bearingsare introduced. The master-slave working style is used and the parameters of thecontroller can be revised on line. The on-line optimal control method according torotating speed is presented. Because the dynamics property of AMB rotor and thenonlinear of amplifier is the function of rotating speed, we can optimize the controlleron the basis of rotating speed in order to make AMBs works on the optimumconditions. The simulation and optimal theory were employed to get the digitalcontroller抯 optimal parameters, which were verified by test preliminarily.The critical speed, the unbalance response of the rotor suspended by the AMBs,the attenuation coefficient and damped natural frequency of the AMB system areanalyzed by the synthetic analysis method of the Active Magnetic Bearings-flexiblerotor system. Results show that the AMBs with PDD controller can increase the stablemargin at high speed and decrease the average amplitude of the rotor抯 unbalanceresponse much better than with PD controller. Because of the difference of locationsbetween the sensors and the magnetic bearings, the observability and controllabilityare affected, so that the characteristics of the systems, particularly when near thebending mode critical speed, are affected.
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