Modal damping identification of a gyroscopic rotor in active magnetic bearings
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SIRM 2015 - 11th International Conference on Vibrations in Rotating Machines, Magdeburg, Germany, February 23-25, 2015
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Modal testing is done for a rotor in active magnetic bearings whose first backward gyroscopic mode is prone to instability. In the absence of process forces, the rotor is excited from one of its active magnetic bearings, and modal parameters are identified at rotational speeds up to 60000 rpm. Experiments are done with excitation directions x and y and for different versions of the active magnetic bearing position controller. The excitation current consists of a series of triangular impulses; the frequency spectrum of the windowed excitation signal contains a narrow band that covers the first backward and forward gyroscopic modes of the rotor. Within this frequency band, natural frequencies, damping ratios, and mode shapes are identified. The results demonstrate the suitability of the chosen excitation and enable a comparison of active magnetic bearing position controllers that should stabilize the first backward gyroscopic mode.