Electromagnetic bearings can support a flexible rotor without any contact and simultaneously influence its dynamics. Such an active suspension and vibration control requires closed-loop control of the rotor motions. In practical applications, the design of the controller is based on a simplified reduced-order model of the mechanical system. As a result, one must deal with the reduced-order control problem. A nonexpansive direct output control scheme for mechanical systems with collocated actuators and sensors (“DCD-control”) is presented. This scheme inherently guarantees stability for the real actively controlled system despite reduced-order control effects like spillover. This concept has been experimentally verified through the active suspension of an elastic rotor by means of two digitally controlled, contactless, electromagnetic bearings. Numerical results of the control design procedure and the full-order system behavior are confirmed by measurements in the experimental setup.

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